Shallow Thoughts : tags : debian

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Tue, 26 Dec 2023

Running Windows 10 under QEMU, Update: Debian Changed OVMF

In October I wrote about making a Windows 10 that Boots off a USB Stick, From Linux.

A Debian update today or yesterday (Merry Christmas!) broke that and I spent a few hours today chasing that down.

There's a package called ovmf that puts BIOS/firmware related files in /usr/share/OVMF/. The command I used in the earlier article included the flag -bios /usr/share/OVMF/OVMF_CODE.fd but as of today, -bios apparently doesn't work any more with any of the files there.

Read more ...

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[ 18:01 Dec 26, 2023    More linux | permalink to this entry | ]

Sun, 01 Oct 2023

Create a Windows 10 that Boots off a USB Stick, from Linux

In 2019, I wrote about struggling to get any sort of Windows booting off an external USB stick, in order to Install Lenovo Firmware Packaged as a .exe on a Linux Machine. I ended up needing to borrow a real Windows machine and install Rufus on it.

In 2023, things are much better. Aki at atkdinosaurus has written a clear, concise tutorial on that topic: How to create a Windows 10 installation on a USB stick in UEFI mode. I love that it's all command-line, so you can duplicate the steps exactly.

Read more ...

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[ 10:07 Oct 01, 2023    More linux | permalink to this entry | ]

Mon, 10 Oct 2022

dpkg-divert: override a file in a Debian package

I boot Linux in text mode, with all the boot-time messages showing. There are several reasons for this, but one is that I want to be able to see any errors that might arise — boot-time errors aren't otherwise shown to the user.

However, many Linux distros, including Debian and Ubuntu, clear the screen before showing a login prompt, making it impossible to read the last few messages or find any errors.

Some years back, I looked into why this was happening, and found the answer in Stop Clearing My God Damned Console. It comes down to a line in getty@tty1.service: TTYVTDisallocate=yes. Change that to TTYVTDisallocate=no and the terminal will stop clearing before you log in.

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[ 19:08 Oct 10, 2022    More linux | permalink to this entry | ]

Fri, 11 Feb 2022

Using a Driverless Printer on Debian (Without Avahi)

It's nice to be back on a relatively minimal Debian install, instead of Ubuntu-with-everything. But one thing that I have to admit I appreciated about Ubuntu: printing "just worked". Turn on a printer, call up the print menu in any app, and the printer I turned on would be there in the menu, without any need of struggling with CUPS configurations.

Ubuntu was using Avahi, the Linux version of Apple's Zeroconf/Bonjour framework, to discover printers. I knew that I'd probably need to install Avahi if I wanted easy printer configuration on Debian. But as it turned out, getting printing working was both harder, and easier.

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[ 18:14 Feb 11, 2022    More linux | permalink to this entry | ]

Mon, 17 Jan 2022

Setting a grub2 Boot Splash Image

For many years, I used extlinux as my boot loader to avoid having to deal with the annoying and difficult grub2. But that was on MBR machines. I never got the sense that extlinux was terribly well supported in the newer UEFI/Secure Boot world. So when I bought my current machine a few years ago, I bit the bullet and let Ubuntu's installer put grub2 on the hard drive.

One of the things I lost in that transition was a boot splash image.

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[ 19:29 Jan 17, 2022    More linux | permalink to this entry | ]

Tue, 28 Dec 2021

Grub2 on a Multi-Boot EFI System

When I bought my new laptop several years ago, I chose Ubuntu as its first distro even though I usually run Debian. For one thing, Ubuntu has an excellent installer. Second, they seem to do more testing on cutting-edge hardware, so I thought the chances were better that hardware on a brand-new laptop would be supported.

Ubuntu has been working fine for a couple of years, but with 21.10 ("Impish Indri") it took a precipitous downturn.

Read more ...

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[ 19:53 Dec 28, 2021    More linux | permalink to this entry | ]

Thu, 23 Aug 2018

Making Sure the Debian Kernel is Up To Date

I try to avoid Grub2 on my Linux machines, for reasons I've discussed before. Even if I run it, I usually block it from auto-updating /boot since that tends to overwrite other operating systems. But on a couple of my Debian machines, that has meant needing to notice when a system update has installed a new kernel, so I can update the relevant boot files. Inevitably, I fail to notice, and end up running an out of date kernel.

But didn't Debian use to have a /boot/vmlinuz that always linked to the latest kernel? That was such a good idea: what happened to that?

I'll get to that. But before I found out, I got sidetracked trying to find a way to check whether my kernel was up-to-date, so I could have it warn me of out-of-date kernels when I log in.

That turned out to be fairly easy using uname and a little shell pipery:

# Is the kernel running behind?
kernelvers=$(uname -a | awk '{ print $3; }')
latestvers=$(cd /boot; ls -1 vmlinuz-* | sort --version-sort | tail -1 | sed 's/vmlinuz-//')
if [[ $kernelvers != $latestvers ]]; then
    echo "======= Running kernel $kernelvers but $latestvers is available"
    echo "The kernel is up to date"

I put that in my .login. But meanwhile I discovered that that /boot/vmlinuz link still exists -- it just isn't enabled by default for some strange reason. That, of course, is the right way to make sure you're on the latest kernel, and you can do it with the linux-update-symlinks command.

linux-update-symlinks is called automatically when you install a new kernel -- but by default it updates symlinks in the root directory, /, which isn't much help if you're trying to boot off a separate /boot partition.

But you can configure it to notice your /boot partition. Edit /etc/kernel-img.conf and change link_in_boot to yes:

link_in_boot = yes

Then linux-update-symlinks will automatically update the /boot/vmlinuz link whenever you update the kernel, and whatever bootloader you prefer can point to that image. It also updates /boot/vmlinuz.old to point to the previous kernel in case you can't boot from the new one.

Update: To get linux-update-symlinks to update symlinks to reflect the current kernel, you need to reinstall the package for the current kernel, e.g. apt-get install --reinstall linux-image-4.18.0-3-amd64. Just apt-get install --reinstall linux-image-amd64 isn't enough.

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[ 20:14 Aug 23, 2018    More linux/kernel | permalink to this entry | ]

Thu, 01 Mar 2018

Re-enabling PHP when a Debian system upgrade disables it

I updated my Debian Testing system via apt-get upgrade, as one does during the normal course of running a Debian system. The next time I went to a locally hosted website, I discovered PHP didn't work. One of my websites gave an error, due to a directive in .htaccess; another one presented pages that were full of PHP code interspersed with the HTML of the page. Ick!

In theory, Debian updates aren't supposed to change configuration files without asking first, but in practice, silent and unexpected Apache bustage is fairly common. But for this one, I couldn't find anything in a web search, so maybe this will help.

The problem turned out to be that /etc/apache2/mods-available/ includes four files:

$ ls /etc/apache2/mods-available/*php*

The appropriate files are supposed to be linked from there into /etc/apache2/mods-enabled. Presumably, I previously had a link to ../mods-available/php7.0.* (or perhaps 7.1?); the upgrade to PHP 7.2 must have removed that existing link without replacing it with a link to the new ../mods-available/php7.2.*.

The solution is to restore those links, either with ln -s or with the approved apache2 commands (as root, of course):

# a2enmod php7.2
# systemctl restart apache2

Whew! Easy fix, but it took a while to realize what was broken, and would have been nice if it didn't break in the first place. Why is the link version-specific anyway? Why isn't there a file called /etc/apache2/mods-available/php.* for the latest version? Does PHP really change enough between minor releases to break websites? Doesn't it break a website more to disable PHP entirely than to swap in a newer version of it?

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[ 10:31 Mar 01, 2018    More linux | permalink to this entry | ]

Sat, 26 Mar 2016

Debian: Holding packages you build from source, and rebuilding them easily

Recently I wrote about building the Debian hexchat package to correct a key binding bug.

I built my own version of the hexchat packages, then installed the ones I needed:

dpkg -i hexchat_2.10.2-1_i386.deb hexchat-common_2.10.2-1_all.deb hexchat-python_2.10.2-1_i386.deb hexchat-perl_2.10.2-1_i386.deb

That's fine, but of course, a few days later Debian had an update to the hexchat package that wiped out my changes.

The solution to that is to hold the packages so they won't be overwritten on the next apt-get upgrade:

aptitude hold hexchat hexchat-common hexchat-perl hexchat-python

If you forget which packages you've held, you can find out with aptitude:

aptitude search '~ahold'

Simplifying the rebuilding process

But now I wanted an easier way to build the package. I didn't want to have to search for my old blog post and paste the lines one by one every time there was an update -- then I'd get lazy and never update the package, and I'd never get security fixes.

I solved that with a zsh function:

newhexchat() {
    # Can't set errreturn yet, because that will cause mv and rm
    # (even with -f) to exit if there's nothing to remove.
    cd ~/outsrc/hexchat
    echo "Removing what was in old previously"
    rm -rf old
    echo "Moving everything here to old/"
    mkdir old
    mv *.* old/

    # Make sure this exits on errors from here on!
    setopt localoptions errreturn

    echo "Getting source ..."
    apt-get source hexchat
    cd hexchat-2*
    echo "Patching ..."
    patch -p0 < ~/outsrc/hexchat-2.10.2.patch
    echo "Building ..."
    debuild -b -uc -us
    echo 'Installing' ../hexchat{,-python,-perl}_2*.deb
    sudo dpkg -i ../hexchat{,-python,-perl}_2*.deb

Now I can type newhexchat and pull a new version of the source, build it, and install the new packages.

How do you know if you need to rebuild?

One more thing. How can I find out when there's a new version of hexchat, so I know I need to build new source in case there's a security fix?

One way is the Debian Package Tracking System. You can subscribe to a package and get emails when a new version is released. There's supposed to be a package tracker web interface, e.g. package tracker: hexchat with a form you can fill out to subscribe to updates -- but for some packages, including hexchat, there's no form. Clicking on the link for the new package tracker goes to a similar page that also doesn't have a form.

So I guess the only option is to subscribe by email. Send mail to containing this line:

subscribe hexchat [your-email-address]
You'll get a reply asking for confirmation.

This may turn out to generate too much mail: I've only just subscribed, so I don't know yet. There are supposedly keywords you can use to limit the subscription, such as upload-binary and upload-source, but the instructions aren't at all clear on how to include them in your subscription mail -- you say keyword, or keyword your-email, so where do you put the actual keywords you want to accept? They offer no examples.

Use apt to check whether your version is current

If you can't get the email interface to work or suspect it'll be too much email, you can use apt to check whether the current version in the repository is higher than the one you're running:

apt-cache policy hexchat

You might want to automate that, to make it easy to check on every package you've held to see if there's a new version. Here's a little shell function to do that:

# Check on status of all held packages:
check_holds() {
    for pkg in $( aptitude search '~ahold' | awk '{print $2}' ); do
        policy=$(apt-cache policy $pkg)
        installed=$(echo $policy | grep Installed: | awk '{print $2}' )
        candidate=$(echo $policy | grep Candidate: | awk '{print $2}' )
        if [[ "$installed" == "$candidate" ]]; then
            echo $pkg : nothing new
            echo $pkg : new version $candidate available

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[ 11:11 Mar 26, 2016    More linux | permalink to this entry | ]

Thu, 17 Mar 2016

Changing X brightness and gamma with xrandr

I switched a few weeks ago from unstable ("Sid") to testing ("Stretch") in the hope that my system, particularly X, would break less often. The very next day, I updated and discovered I couldn't use my system at night any more, because the program I use to reduce the screen brightness by tweaking X gamma no longer worked. Neither did other related programs, such as xgamma and xcalib.

The Dell monitor I use doesn't have reasonable hardware brightness controls: strangely, the brightness button works when the monitor is connected over VGA, but if I want to use the sharper HDMI connection, brightness adjustment no longer works. So I depend on software brightness adjustment in order to use my computer at night when the room is dim.

Fortunately, it turns out there's a workaround. xrandr has options for both brightness and gamma:

xrandr --output HDMI1 --brightness .5
xrandr --output HDMI1 --gamma .5:.5:.5

I've always put xbrightness on a key, so I can use a function key to adjust brightness interactively up and down according to conditions. So a command that sets brightness to .5 or .8 isn't what I need; I need to get the current brightness and set it a little brighter or a little dimmer. xrandr doesn't offer that, so I needed to script it.

You can get the current brightness with

xrandr --verbose | grep -i brightness

But I was hoping there would be a more straightforward way to get brightness from a program. I looked into Python bindings for xrandr; there are some, but with no documentation and no examples. After an hour of fiddling around, I concluded that I could waste the rest of the day poring through the source code and trying things hoping something would work; or I could spend fifteen minutes using to wrap the command-line xrandr.

So subprocesses it was. It made for a nice short script, much simpler than the old xbrightness C program that used <X11/extensions/xf86vmode.h> and XF86VidModeGetGammaRampSize(): xbright on github.

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[ 11:01 Mar 17, 2016    More linux | permalink to this entry | ]

Fri, 05 Feb 2016

Updating Debian under a chroot

Debian's Unstable ("Sid") distribution has been terrible lately. They're switching to a version of X that doesn't require root, and apparently the X transition has broken all sorts of things in ways that are hard to fix and there's no ETA for when things might get any better.

And, being Debian, there's no real bug system so you can't just CC yourself on the bug to see when new fixes might be available to try. You just have to wait, try every few days and see if the system

That's hard when the system doesn't work at all. Last week, I was booting into a shell but X wouldn't run, so at least I could pull updates. This week, X starts but the keyboard and mouse don't work at all, making it hard to run an upgrade. has been fixed.

Fortunately, I have an install of Debian stable ("Jessie") on this system as well. When I partition a large disk I always reserve several root partitions so I can try out other Linux distros, and when running the more experimental versions, like Sid, sometimes that's a life saver. So I've been running Jessie while I wait for Sid to get fixed. The only trick is: how can I upgrade my Sid partition while running Jessie, since Sid isn't usable at all?

I have an entry in /etc/fstab that lets me mount my Sid partition easily:

/dev/sda6 /sid ext4 defaults,user,noauto,exec 0 0
So I can type mount /sid as myself, without even needing to be root.

But Debian's apt upgrade tools assume everything will be on /, not on /sid. So I'll need to use chroot /sid (as root) to change the root of the filesystem to /sid. That only affects the shell where I type that command; the rest of my system will still be happily running Jessie.

Mount the special filesystems

That mostly works, but not quite, because I get a lot of errors like permission denied: /dev/null.

/dev/null is a device: you can write to it and the bytes disappear, as if into a black hole except without Hawking radiation. Since /dev is implemented by the kernel and udev, in the chroot it's just an empty directory. And if a program opens /dev/null in the chroot, it might create a regular file there and actually write to it. You wouldn't want that: it eats up disk space and can slow things down a lot.

The way to fix that is before you chroot: mount --bind /dev /sid/dev which will make /sid/dev a mirror of the real /dev. It has to be done before the chroot because inside the chroot, you no longer have access to the running system's /dev.

But there is a different syntax you can use after chrooting:

mount -t proc proc proc/
mount --rbind /sys sys/
mount --rbind /dev dev/

It's a good idea to do this for /proc and /sys as well, and Debian recommends adding /dev/pts (which must be done after you've mounted /dev), even though most of these probably won't come into play during your upgrade.

Mount /boot

Finally, on my multi-boot system, I have one shared /boot partition with kernels for Jessie, Sid and any other distros I have installed on this system. (That's somewhat hard to do using grub2 but easy on Debian though you may need to turn off auto-update and Debian is making it harder to use extlinux now.) Anyway, if you have a separate /boot partition, you'll want it mounted in the chroot, in case the update needs to add a new kernel. Since you presumably already have the same /boot mounted on the running system, use mount --bind for that as well.

So here's the final set of commands to run, as root:

mount /sid
mount --bind /proc /sid/proc
mount --bind /sys /sid/sys
mount --bind /dev /sid/dev
mount --bind /dev/pts /sid/dev/pts
mount --bind /boot /sid/boot
chroot /sid

And then you can proceed with your apt-get update, apt-get dist-upgrade etc. When you're finished, you can unmount everything with one command:

umount --recursive /sid

Some helpful background reading:

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[ 11:43 Feb 05, 2016    More linux/install | permalink to this entry | ]

Sun, 27 Dec 2015

Extlinux on Debian Jessie

Debian "Sid" (unstable) stopped working on my Thinkpad X201 as of the last upgrade -- it's dropping mouse and keyboard events. With any luck that'll get straightened out soon -- I hear I'm not the only one having USB problems with recent Sid updates. But meanwhile, fortunately, I keep a couple of spare root partitions so I can try out different Linux distros. So I decided to switch to the current Debian stable version, "Jessie".

The mouse and keyboard worked fine there. Except it turned out I had never fully upgraded that partition to the "Jessie"; it was still on "Wheezy". So, with much trepidation, I attempted an apt-get update; apt-get dist-upgrade

After an interminable wait for everything to download, though, I was faced with a blue screen asking this:

No bootloader integration code anymore.
The extlinux package does not ship bootloader integration anymore.
If you are upgrading to this version of EXTLINUX your system will not boot any longer if EXTLINUX was the only configured bootloader.
Please install GRUB.

No -- it's not okay! I have good reasons for not using grub2 -- besides which, extlinux on exact machine has been working fine for years under Debian Sid. If it worked on Wheezy and works on Sid, why wouldn't it work on the version in between, Jessie?

And what does it mean not to ship "bootloader integration", anyway? That term is completely unclear, and googling was no help. There have been various Debian bugs filed but of course, no explanation from the developers for exactly what does and doesn't work.

My best guess is that what Debian means by "bootloader integration" is that there's a script that looks at /boot/extlinux/extlinux.conf, figures out which stanza corresponds to the current system, figures out whether there's a new kernel being installed that's different from the one in extlinux.conf, and updates the appropriate kernel and initrd lines to point to the new kernel.

If so, that's something I can do myself easily enough. But what if there's more to it? What would actually happen if I upgraded the extlinux package?

Of course, there's zero documentation on this. I found plenty of questions from people who had hit this warning, but most were from newbies who had no idea what extlinux was or why their systems were using it, and they were advised to install grub. I only found one hit from someone who was intentionally using extlinux. That person aborted the install, held back the package so the potentially nonbooting new version of extlinux wouldn't be installed, then updated extlinux.conf by hand, and apparently that worked fine.

It sounded like a reasonable bet. So here's what I did (as root, of course):

It worked fine. I booted into jessie with the kernel I had specified. And hooray -- my keyboard and mouse work, so I can continue to use my system until Sid becomes usable again.

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[ 17:28 Dec 27, 2015    More linux/install | permalink to this entry | ]

Sun, 09 Jun 2013

Debugging a Firefox freeze on Ringtail and Sid

I recently went on an upgrading spree on my main computer. In the hope of getting more up-to-date libraries, I updated my Ubuntu to 13.04 "Raring Ringtail", and Debian to unstable "Sid". Most things went fine -- except for Firefox.

Under both Ringtail and Sid, Firefox became extremely unstable. I couldn't use it for more than about fifteen minutes before it would freeze while trying to access some web resource. The only cure when that happened was to kill it and start another Firefox. This was happening with the exact same Firefox -- a 21.0 build from -- that I was using without any problems on older versions of Debian and Ubuntu; and with the exact same profile. So it was clearly something that had changed about Debian and Ubuntu.

The first thing I do when I hit a Firefox bug is test with a fresh profile. I have all sorts of Firefox customizations, extensions and other hacks. In fact, the customizations are what keep me tied to Firefox rather than jumping to some other browser. But they do, too often, cause problems. I have a generic profile I keep around for testing, so I fired it up and used it for browsing for a day. Firefox still froze, but not as often.

Disabling Extensions

Was it one of my extensions? I went to the Tools->Add-ons to try disabling them all ... and Firefox froze. Bingo! That was actually good news. Problems like "Firefox freezes a lot" are hard to debug. "Firefox freezes every time I open Tools->Add-ons" are a whole lot easier. Now I needed to find some other way of disabling extensions to see if that helped.

I went to my Firefox profile directory and moved everything in the extensions directory into a new directory I made called extensions.sav. Then I started moving them back one by one, each time starting Firefox and calling up Tools->Add-ons. It turned out two extensions were causing the freeze: Open in Browser and Custom Tab Width. So I left those off for the time being.

Disabling Themes

Along the way, I discovered that clicking on Appearance in Tools->Add-ons would also cause a freeze, so my visual theme was also a problem. This wasn't something I cared about: some time back when Mozilla started trumpeting their themeability, I clicked around and picked up some theme involving stars and planets. I could live without that.

But how do you disable a theme? Especially if you can't go to Tools->Add-ons->Appearance?

Turns out everything written on the web on this is wrong. First, everything on themes on assumes you can get to that Appearance tab, and doesn't even consider the possibility that you might have to look in your profile and remove a file. Search further and you might find references to files named lightweighttheme-header and lightweighttheme-footer, neither of which existed in my profile.

But I did have a directory called lwtheme. So I removed that, plus four preferences in prefs.js that included the term "lightweightThemes". After a restart, my theme was gone, I was able to view that Appearance tab, and I was able to browse the web for nearly 4 hours before firefox hung again. Darn! That wasn't all of it.

Debugging the environment

But soon after that I had a breakthrough. I discovered a page on my bank's website that froze Firefox every time. But that was annoying for testing, since it required logging in then clicking through several other pages, and you never know what a bank website might decide to do if you start logging in over and over. I didn't want to get locked out.

But then I was checking an episode in one of the podcasts I listen to, which involved going to the link -- and Firefox froze, on a simple RSS link. I restarted and tried again -- another freeze. I'd finally found the Rosetta stone, something that hung Firefox every time. Now I could do some serious testing!

I'd had friends try this using the same version of Firefox and Ubuntu, without seeing a freeze. Was it something about my user environment? I created a new user, switched to another virtual console (Ctrl-Alt-F2) and logged in as my new user, then ran X. This was a handy way to test: I could get to my normal user's X session in Ctrl-Alt-F7, while the new user's X session was on Ctrl-Alt-F8. Since I don't have Gnome or KDE installed on this machine, the new user came up with a default Openbox session. It came up at the wrong resolution -- the X11 in the newest Linux distros apparently doesn't read the HDMI monitor properly -- but I wasn't worried about that.

And when I ran Firefox as the new user (letting it create a new profile) and middlemouse-pasted the BBC RSS URL, it loaded it, without freezing.

Now we're getting somewhere. Now I knew it was something about my user environment.

I tried copying all of ~/.config from my user to the new user. No hang. I tried various other configuration files. Still no hang.

The X initialization

I'll skip some steps here, and just mention that in trying to fix the resolution problem, so I didn't have to do all my debugging at 1024x768, I discovered that if I used my .xinitrc file to start X, I'd get a freezy Firefox. If I didn't use my .xinitrc, and defaulted to the system one, Firefox was fine. Even if I removed everything else from my .xinitrc, and simply ran openbox from it, that was enough to make Firefox hang.

Okay, what was the system doing? I poked around /etc/X11: it was running /etc/X11/Xsession. I copied that file to my .xinitrc and started X. No hang.

Xsession does a bunch of things, but one of the main things it does is run every script in the /etc/X11/Xsession.d directory. So I made a copy of that directory inside my home directory, and modified .xinitrc to execute those files instead. Then I started moving them aside to see which ones made a difference.

And I found it. /etc/X11/Xsession.d/75dbus_dbus-launch was the file that mattered.

75dbus_dbus-launch takes the name of the program that's going to be executed -- in this case that was x-session-manager, which links to /etc/alternatives/x-session-manager, which links to /usr/bin/openbox-session -- and instead runs /usr/bin/dbus-launch --exit-with-session x-session-manager.

Now that I knew that, I moved everything aside and made a little .xinitrc that ran /usr/bin/dbus-launch --exit-with-session openbox-session. And Firefox didn't crash.


So it all comes down to dbus. I was already running dbus: ps shows /usr/bin/dbus-daemon --system running -- and that worked fine for everything dbussy I normally do, like run "gimp image.jpg" and have it open in my already running GIMP.

But on Ringtail and Sid, that isn't enough for Firefox. For some reason, on these newer systems, Firefox requires a second dbus daemon -- it shows up in ps as /usr/bin/dbus-daemon --fork --print-pid 5 --print-address 7 --session -- for the X session. If it doesn't have that, it's fine for a while, and then, hours later, it will mysteriously freeze while waiting for a network resource.

Why? I have no idea. No one I've asked seems to know anything about how dbus works, the difference between system and session dbus daemons, or why any of it it would have this effect on Firefox.

I filed a Firefox bug, Bug 881122, though I don't have much hope of anyone being interested in a bug that only affects Linux users using nonstandard X sessions. But maybe I'm not the only one. If your Firefox is hanging and you found your way here, I hope I've given you some ideas. And if anyone has a clue as to what's really happening and why dbus would have that effect, I'd love to hear from you.

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[ 20:08 Jun 09, 2013    More linux | permalink to this entry | ]

Wed, 15 May 2013

Finding versions of installed packages in Debian/Ubuntu

Checking versions in Debian-based systems is a bit of a pain.

This happens to me a couple of times a month: for some reason I need to know what version of something I'm currently running -- often a library, like libgtk. aptitude show will tell you all about a package -- but only if you know its exact name. You can't do aptitude show libgtk or even aptitude show '*libgtk*' -- you have to know that the package name is libgtk2.0-0. Why is it libgtk2.0-0? I have no idea, and it makes no sense to me.

So I always have to do something like aptitude search libgtk | egrep '^i' to find out what packages I have installed that matches the name libgtk, find the package I want, then copy and paste that name after typing aptitude show.

But it turns out it's super easy in Python to query Debian packages using the Python apt package. In fact, this is all the code you need:

import sys
import apt

cache = apt.cache.Cache()

pat = sys.argv[1]

for pkgname in cache.keys():
    if pat in pkgname:
        pkg = cache[pkgname]
        instver = pkg.installed
        if instver:
            print, instver.version
Then run aptver libgtk and you're all set.

In practice, I wanted nicer formatting, with columns that lined up, so the actual script is a little longer. I also added a -u flag to show uninstalled packages as well as installed ones. Amusingly, the code to format the columns took about twice as many lines as the code that does the actual work. There doesn't seem to be a standard way of formatting columns in Python, though there are lots of different implementations on the web. Now there's one more -- in my aptver on github.

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[ 16:07 May 15, 2013    More linux | permalink to this entry | ]

Wed, 14 Nov 2012

How To Satisfy Debian Dependencies Without Installing The Stupid Package

(This is a guest post by David North.)

Debian developers tend to get overzealous in their dependency lists, probably to avoid constant headaches from fringe cases whose favorite programs fail because they also need some obscure library or package support (and yes, I'm talking to you, Ubuntu). But what if you don't want some goofy dependency (and the cascade of other crap it pulls in?)

As a small aside, aptitude/apt-get hold <pkg> is terrific if you just want to keep a package at a pre-horkage level, but for some obcure reason you can't "hold" a package that isn't installed. So that won't work as of 11/2012.

You can however generate an equivalent package with a higher version number and install it, which naturally blocks the offending package. Even better, the replacement package need do nothing at all other than satisfy the apt database. Even better, the whole thing is incredibly simple.

First install the "equivs" package. This will deliver two programs:

Officially you should start with 'equivs-control <:pkgname>' which will create a file 'pkgname' in the current directory. Inside are various fields but you only need eight and can simply delete the rest. Here's approximately what you should end up with for a fictional package "pkgname":

Section: misc
Priority: optional
Standards-Version: 3.9.2

Package: pkgname
Version: 1:42
Maintainer: Your Name <your@email.address>
Architecture: all
Description: fake pkgname to block a dumb dependency

The first three lines are just boilerplate, though you may have to increment the standards-version at some point if you reuse the file. No changes are needed now.

The pkgname does actually have to match the name of the package you want to block. The version must be higher than that of the target package. Maintainer need not be you, but it's a good idea to at least use a name you recognize as yourself. Architecture can be left as "all" unless you're doing something extra tricky. Description is not necessary but a good idea; put your notes here.

The only trick is the version. Note the 1:42 structure here. The first number is the "epoch" in debian-speak, and may or may not be used. In practice I've never seen an epoch greater than one, so I suggest using either 1 or 2 here rather than just leaving it blank. You can see the epoch number in a package when you use aptitude show <pkgname>. The version is the number immediately after the colon, and for safety's sake should be considerably larger than the version you're trying to block (to avoid future updates). I like to use "42" for obvious reasons unless the actual package version is too close. Factoid: if no "epoch" is indicated debian will assume epoch 0, which will not show up as a zero in a .deb (or in aptitude show) but rather as a blank. The version number will have no colon in this event.

Having done this, all you need do is issue the command 'equivs-build path-to-pkgname' (preferably from the same directory) and you get a fake deb to install with dpkg -i. Say goodbye to the dependency.

One more trick: once you have your file <pkgname> with the Eight Important Fields, you can pretty much skip using equivs-control. All it does is make the initial text file, and it will be easier to edit the one you already have with a new package name (and rename the file at the same time). Note, however, this handy file will not necessarily be useful on other debian-based systems or later installs, so running equivs-control after a big upgrade or moving to another distro is very good practice. If you compare the files and they have the same entries, great. If not, use the new ones.

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[ 11:50 Nov 14, 2012    More linux/install | permalink to this entry | ]

Sat, 16 Jun 2012

Setting the default browser when update-alternatives fails

I ran ubuntu-bug to report a bug. After collecting some dependency info, the program asked me if I wanted to load the bug report page in a browser. Of course I did -- but it launched chromium, where I don't have any of my launchpad info loaded, rather than firefox.

So how do you change the default browser in Ubuntu? The program that controls that, and lots of similar defaults, is update-alternatives.

update-alternatives with no arguments gives a long usage statement that isn't too clear. You need to know the various category names ("groups") before you can do much. Here's how to get a list of all the groups:

update-alternatives --get-selections

But that's still a long list. To find the entries that might be pointing to chrome or chromium, I narrowed it down:

update-alternatives --get-selections | grep chrom

That narrowed it down: x-www-browser and gnome-www-browser both pointed to chromium. So let's try to change that to firefox:

$ update-alternatives --set gnome-www-browser /usr/local/firefox11/firefox
update-alternatives: error: alternative /usr/local/firefox11/firefox for gnome-www-browser not registered, not setting.

Whoops! The problem here is that I'm running a firefox installed from, not the one that comes with Ubuntu. What if I want to make that my default browser? What does it mean for an application to be "registered"?

Well, no one seems to have documented that. I found it discussed briefly here: What is Ubuntu's Definition of a “Registered Application”?, but the only solutions seemed to involve hand-editing desktop files to add icons, and there's no easy way to figure out how much of the desktop file it needs. That sounded way too complicated.

Thanks to Lyz and Maco for the real answer: skip update-alternatives entirely, and change the symbolic links in /etc/alternatives by hand.

$ sudo rm /etc/alternatives/gnome-www-browser
$ sudo ln -s /usr/local/firefox11/firefox /etc/alternatives/gnome-www-browser
$ sudo rm /etc/alternatives/x-www-browser
$ sudo ln -s /usr/local/firefox11/firefox /etc/alternatives/x-www-browser 

That was much simpler, and worked fine: now applications that need to call up a browser will use firefox instead of chromium.

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[ 17:04 Jun 16, 2012    More linux | permalink to this entry | ]

Sat, 26 May 2012

Use stdeb to make Debian packages for a Python package

I write a lot of little Python scripts. And I use Ubuntu and Debian. So why aren't any of my scripts packaged for those distros?

Because Debian packaging is absurdly hard, and there's very little documentation on how to do it. In particular, there's no help on how to take something small, like a Python script, and turn it into a package someone else could install on a Debian system. It's pretty crazy, since RPM packaging of Python scripts is so easy.

Recently at the Ubuntu Developers' Summit, Asheesh of OpenHatch pointed me toward a Python package called stdeb that simplifies a lot of the steps and makes Python packaging fairly straightforward.

You'll need a file to describe your Python script, and you'll probably want a .desktop file and an icon. If you haven't done that before, see my article on Packaging Python for MeeGo for some hints.

Then install python-stdeb. The package has some requirements that aren't listed as dependencies, so you'll need to install:

apt-get install python-stdeb fakeroot python-all
(I have no idea why it needs python-all, which installs only a directory /usr/share/doc/python-all with some policy documentation files, but if you don't install it, stdeb will fail later.)

Now create a config file for stdeb to tell it what Debian/Ubuntu version you're going to be targeting, if it's anything other than Debian unstable (stdeb's default). Unfortunately, there seems to be no way to pass this on the command line rather than in a config file. So if you want to make packages for several distros, you'll have to edit the config file for every distro you want to support. Here's what I'm using for Ubuntu 12.04 Precise Pangolin:

Suite: precise

Now you're ready to run stdeb. I know of two ways to run it. You can generate both source and binary packages, like this:

python --command-packages=stdeb.command bdist_deb
Or you can generate source packages only, like this:
python --command-packages=stdeb.command sdist_dsc

Either syntax creates a directory called deb_dist. It contains a lot of files including a source .dsc, several tarballs, a copy of your source directory, and (if you used bdist_deb) a binary .deb package.

If you used the bdist_deb form, don't be put off that it concludes with a message:

dpkg-buildpackage: binary only upload (no source included)
It's fibbing: the source .dsc is there as well as the binary .deb. I presume it prints the warning because it creates them as separate steps, and the binary is the last step.

Now you can use dpkg -i to install your binary deb, or you can use the source dsc for various purposes, like creating a repository or a Launchpad PPA. But those involve a lot more steps -- so I'll cover that in a separate article about creating PPAs.

Update: you can find that article here: Creating packages for a Launchpad PPA.

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[ 11:44 May 26, 2012    More programming | permalink to this entry | ]

Thu, 24 Nov 2011

Configuring extlinux's auto-update on Debian

A few days ago, I wrote about how to set up and configure extlinux (syslinux) as a bootloader. But on Debian or Ubuntu, if you make changes to files like /boot/extlinux/extlinux.conf directly, they'll be overwritten.

The configuration files are regenerated by a program called extlinux-update, which runs automatically every time you update your kernel. (Specifically, it runs from the postinst script of the linux-base package: you can see it in /var/lib/dpkg/info/linux-base.postinst.)

So what's a Debian user to do if she wants to customize the menus, add a splash image or boot other operating systems?

First, if you decide you really don't want Debian overwriting your configuration files, you can change disable updates by editing /etc/default/extlinux. Just be aware you won't get your boot menu updated when you install new kernels -- you'll have to remember to update them by hand.

It might be worth it: the automatic update is nearly as annoying as the grub2 updater: it creates two automatic entries for every kernel you have installed. So if you have several distros installed, each with a kernel or two in your shared /boot, you'll get an entry to boot Debian Squeeze with the Ubuntu Oneiric kernel, one for Squeeze with the Natty kernel, one for Squeeze with the Fedora 16 kernel ... as well as entries for every kernel you have that's actually owned by Debian. And then for each of these, you'll also get a second entry, to boot in recovery mode. If you have several distros installed, it makes for a very long and confusing boot menu!

It's a shame that the auto-updater doesn't restrict itself to kernels managed by the packaging system, which would be easy enough to do. (Wonder if they would accept a patch?) You might be able to fudge something that works right by setting up symlinks so that the only readable kernels actually live on the root partition, so Debian can't read the kernels from the other distros. Sounds a bit complicated and I haven't tried it. For now, I've turned off automatic updating on my system.

But if your setup is simpler -- perhaps just one Debian or one Ubuntu partition plus some non-Linux entries such as BSD or Windows -- here's how to set up Debian-style automatic updating and still keep all your non-Linux boot entries and your nice menu customizations.

Debian automatic updates and themes

First, take a quick look at /etc/default/extlinux and customize anything there you might need, like the names of the kernels, kernel boot parameters or timeout. See man extlinux-update for details.

For configuring menu colors, image backgrounds and such, you'll need to make a theme. You can see a sample theme by installing the package syslinux-themes-debian -- but watch out. If you haven't configured apt not to pull in suggested packages, that may bring back grub or grub-legacy, which you probably don't want.

You can make a theme without needing that package, though. Create a directory /usr/share/syslinux/themes/mythemename (the extlinux-update man page claims you can put a theme anywhere and specify it by its full path, but it lies). Create a directory called extlinux inside it, and make a file with everything you want from extlinux.conf. For example:

default 0
prompt 1
timeout 50

ui vesamenu.c32
menu title Welcome to my Linux machine!
menu background mysplash.png
menu color title 1;36 #ffff8888 #00000000 std
menu color unsel 0    #ffffffff #00000000 none
menu color sel   7    #ff000000 #ffffff00 none

include linux.cfg
menu separator
include themes/mythemename/other.cfg

Note that last line: you can include other files from your theme. For instance, you can create a file called other.cfg with entries for other partitions you want to boot:

label oneiric
menu label Ubuntu Oneiric Ocelot
kernel /vmlinuz-3.0.0-12-generic
append initrd=/initrd.img-3.0.0-12-generic root=UUID=c332b3e2-5c38-4c50-982a-680af82c00ab ro quiet

label fedora
menu label Fedora 16
kernel /vmlinuz-3.1.0-7.fc16.i686
append initrd=/initramfs-3.1.0-7.fc16.i686.img root=UUID=47f6b1fa-eb5d-4254-9fe0-79c8b106f0d9 ro quiet

menu separator

LABEL Windows
KERNEL chain.c32
APPEND hd0 1

Of course, you could have a debian.cfg, an ubuntu.cfg, a fedora.cfg etc. if you wanted to have multiple distros all keeping their kernels up-to-date. Or you can keep the whole thing in one file, theme.cfg. You can make a theme as complex or as simple as you like.

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[ 12:26 Nov 24, 2011    More linux/install | permalink to this entry | ]

Tue, 25 Oct 2011

Creating a multi-distro Linux Live USB stick

Linux live USB sticks (flash drivers) are awesome. You can carry them anywhere and give a demo of Linux on anyone's computer, any time. But how do you keep track of them? Especially since USB sticks don't have any place to write a label. How do you remember that the shiny blue stick is the one with Ubuntu Oneiric, the black one has Ubuntu Lucid, the other blue one that's missing its top is Debian ... and so forth. It's impossible! Plus, such a waste -- you can hardly buy a flash drive smaller than 4G these days, and then you go and devote it to a 700Mb ISO designed to fit on a CD. Silly.

The answer: get one big USB stick and put lots of distros on it, using grub to let you choose at boot time.

To create my stick, I followed the easy instructions at HOWTO: Booting LiveCD ISOs from USB flash drive with Grub2. I found that tutorial quite simple, so I'm not going to duplicate the instructions there. I used the non-LUA version, since my grub on Ubuntu Natty didn't seem to support LUA. Basically you run grub-install to the stick, create a directory called iso where you stick all your ISO files, then create a grub.cfg with magic incantations to boot each ISO.

Ah, wait ... magic incantations? The tutorial is missing one important part: what if you want to use an ISO that isn't already mentioned in the tutorial? If Ubuntu's entry is
linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet splash noprompt -- and Parted Magic's is
linux (loop)/pmagic/bzImage iso_filename=$isofile edd=off noapic load_ramdisk=1 prompt_ramdisk=0 rwnomce sleep=10 loglevel=0 then you know there's some magic going on there.

I knew I needed at least the Ubuntu "alternate installer", since it allows installing a command-line system without the Unity desktop, and Debian Squeeze, since that's currently the most power-efficient Linux for laptops, in addition to the distros mentioned in the tutorial. How do you figure out what to put in those grub.cfg lines? Here's how to figure it out from the ISO file. I'll use the Debian Squeeze ISO as an example.

Step 1: mount the ISO file.

$ sudo mount -o loop /pix/boot/isos/debian-6.0.0-i386-netinst.iso /mnt

Step 2: find the kernel

$ ls /mnt/*/vmlinuz /mnt/*/bzImage

Step 3: find the initrd. It might have various names, and might or might not be compressed, but the name will almost always start with init.

$ ls /mnt/*/vmlinuz /mnt/*/init*

Unmount the ISO file.

$ umount /mnt

The trick in steps 2 and 3 is that nearly all live ISO images put the kernel and initrd a single directory below the root. If you're using an ISO that doesn't, you may have to search more deeply (try /mnt/*/*).

In the case of Debian Squeeze, now I have the two filenames: /install.386/vmlinuz and /install.386/initrd.gz. (I've removed the /mnt part since that won't be there when I'm booting from the USB stick.) Now I can edit boot/grub/grub.cfg and make a boot stanza for Debian:

menuentry "Debian Squeeze" {
    set isofile="/boot/isos/debian-6.0.0-i386-netinst.iso"

    loopback loop $isofile 
    linux (loop)/install.386/vmlinuz iso_filename=$isofile quiet splash noprompt --
    initrd (loop)/install.386/initrd.gz

Here's the entry for the Ubuntu alternate installer:

menuentry "Oneiric 11.10 alternate" {
    set isofile="/boot/isos/ubuntu-11.10-alternate-i386.iso"
    loopback loop $isofile 
    linux (loop)/install/vmlinuz iso_filename=$isofile
    initrd (loop)/install/initrd.gz

It sounds a little convoluted, I know -- but you only have to do it once, and then you have this amazing keychain drive with every Linux distro on it you can think of. Amaze your friends!

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[ 22:21 Oct 25, 2011    More linux/install | permalink to this entry | ]

Sat, 27 Aug 2011

Vaio tips for Debian Squeeze

I switched to the current Debian release, "Squeeze", quite a few months ago on my Sony Vaio laptop. I've found that Squeeze, with its older kernel and good attention to power management (compared to the power management regressions in more recent kernels), gets much better battery life than either Arch Linux or Ubuntu on this machine. I'm using Squeeze as the primary OS at least until the other distros get their kernel power management sorted out.

I did have to solve a couple of minor problems when switching over, though.

Suspend/Resume quirks

The first problem was that my Vaio TX650 would freeze on resuming from suspend -- something that every other Linux distro has handled out of the box on this machine.

The solution turned out to be simple though non-obvious, apparently a problem with controlling power to the display:

sudo pm-suspend --quirk-dpms-on

That wasn't easy to find, but ever since then the machine has been suspending without a single glitch. And it's a true suspend, unlike Ubuntu Natty, which on this machine will use up a full battery if I leave it suspended all day -- Natty uses nearly as much power when suspended as it does running.

Adjusting screen brightness: debugging ACPI

Of course, once I got that sorted out, there were the usual collection of little changes I needed to make. Number one was that it didn't automatically handle brightness adjustment with the Fn-F5 and Fn-F6 keys.

It turned out my previous technique for handling the brightness keys didn't work, because the names of the ACPI events in /etc/acpi/events had changed. Previously, /etc/acpi/events/sony-brightness-down had contained references to the Sony I/O Control, or SPIC:

event=sony/hotkey SPIC 00000001 00000010
action=/etc/acpi/ down
That device didn't exist on Squeeze. To find out what I needed now, I ran acpi-listen and typed the function-key combos in question. That gave me the codes I needed. I changed the sony-brightness-down file to read:
event=video/brightnessdown BRTDN 00000087 00000000
action=/etc/acpi/ down

It's probably a good thing, changing to be less Sony-specific ... but as a user it's one of those niggling annoyances that I have to go chase down every time I upgrade to a new Linux version.

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[ 12:07 Aug 27, 2011    More linux/laptop | permalink to this entry | ]

Tue, 22 Mar 2011

Installing Debian Squeeze

Over the weekend I tried installing Debian's new release, "Squeeze", on my Vaio TX650 laptop.

I used a "net install" CD, the one that installs only the bare minimum then goes to the net for anything else. I used Expert mode, because I needed to set a static IP address and keep it from overwriting my grub configuration.

Most of the install went smoothly -- until I got to the last big step near the end, "Select and install software", where it froze at 1%.

A little web searching (on another machine) gave me the hint that the Debian installer prints a log on the fourth console, Ctrl-Alt-F4. Checking that log made the problem clear: aptitude was complaining about packages without a proper GPG signature -- type Yes to continue without verifying signatures. But since this was running inside the installer, there's no place to type Yes -- that Ctrl-Alt-F4 console is merely displaying messages, not accepting input, and the installer doesn't accept any input for aptitude.

Fortunately, "Select and install software" isn't crucial to the net install process. I don't actually know what software it would have installed -- it never asked me to choose any -- but without it, you should still have a working minimal Debian on the disk. So I made another console on Ctrl-Alt-F2, ran ps aux, found that aptitude was the highest numbered process running, and killed it. Upon returning to the installer (Ctrl-Alt-F1), I was able to skip "Select and install software", finish the install process and reboot.

Upon rebooting, I logged in as root and ran apt-get update. It complained about GPG errors; but now I could do something about it. I ran apt-get upgrade and confirmed that I wanted to proceed even without verifying package signatures. When that was over, the problem was fixed: a subsequent apt-get update ran without errors.

This ISO was downloaded (from the mirror, I believe) a few days after the official release. I'm told that Debian changes the keys at the last minute before a release; perhaps the new keys don't make it into the ISO images on all the mirrors. Or maybe they just messed up with the Squeeze release.

Anyway, it was fairly easily solved, but seemed like a disappointing and silly problem. A web search found lots of people people hitting this problem; it's a shame that the installer can't run aptitude in a mode where it won't prompt and hang up the whole install.

Alas, it's probably all academic anyway, since suspend/resume doesn't work. It freezes on resume, with a black screen -- another common Debian problem, judging by what I see on the net. I'm a bit surprised, since every other distro I've tried has suspended the Vaio beautifully. But after hours of messing with it over the weekend, I ran out of time and conceded defeat.

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[ 22:49 Mar 22, 2011    More linux/install | permalink to this entry | ]

Sun, 20 Mar 2011

Making CapsLock equal Control in Debian Squeeze

It's time for another installment of "Where have the control/capslock adjustments migrated to?" This time it's for the latest Debian release, "Squeeze".

Ever since they stopped making keyboards with the control key to the left of the A, I've remapped my CapsLock key to be another Control key. I never need CapsLock, but I use Control constantly all day while editing text. Some people prefer to swap Control and CapsLock.

But the right way to do that changes periodically. For the last few years, since Ubuntu Intrepid, you could set XKbOptions for Control and Capslock in /etc/default/console-setup. But that no longer works in Squeeze.

It turns out Squeeze introduced a new file, /etc/default/keyboard, so any keyboard options previously had in console-setup need to move to keyboard. For me, that's these lines:

though I suspect only the last line matters.

This wasn't well covered on the web. There aren't many howtos covering Squeeze yet, but I found the hint I needed in a terse Debian IRCbot factoid: Factoid capslock says

For console-setup, append ",ctrl:nocaps" to the value of XKBOPTIONS within /etc/default/console-setup (/etc/default/keyboard on Squeeze).

That factoid assumes you already have XKBOPTIONS set; as shipped, it's empty, so skip that initial comma.

I was going to conclude with a link to the documentation on XKBOPTIONS, or XKbOptions as it was capitalized in xorg.conf ... but there doesn't seem to be any. It's not in any of the Xorg man pages like xorg.conf(5) where I expected to find it; nor can I find anything on the web beyond howtos like this one from people who have figured out a few specific options. Anyone know?

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[ 12:54 Mar 20, 2011    More linux/install | permalink to this entry | ]

Mon, 05 Jul 2010

Adventures with Virtual hosts and CGI on Apache 2.2

We had a server that was still running Debian Etch -- for which Debian just dropped support. We would have upgraded that machine to Lenny long ago except for one impediment: upgrading the live web server from apache 1 to apache 2.2.

Installing etch's apache 2.2.3 package and getting the website running under it was no problem. Debian has vastly improved their apache2 setup from years past -- for instance, installing PHP also enables it now, so you don't need to track down all the places it needs to be turned on.

But when we upgraded to Lenny and its apache 2.2.9, things broke. Getting it working again was tricky because most of the documentation is standard Apache documentation, not based on Debian's more complex setup. Here are the solutions we found.

Enabling virtual hosts

As soon as the new apache 2.2.9 was running, we lost all our websites, because the virtual hosts that had worked fine on Etch broke under Lenny's 2.2.9. Plus, every restart complained [warn] NameVirtualHost *:80 has no VirtualHosts.

All the web documentation said that we had to change the <VirtualHost *> lines to <VirtualHost *:80>. But that didn't help. Most documentation also said we would also need the line: NameVirtualHost *:80 Usually people seemed to find it worked best to put that in a newly created file called conf.d/virtualhosts. Our Lenny upgrade had already created that line and put it in ports.conf, but it didn't work either there or in conf.d/virtualhosts.

It turned out the key was to remove the NameVirtualHost *:80 line from ports.conf, and add it in sites-available/default. Removing it from ports was the important step: if it was in ports.conf at all, then it didn't matter if it was also in the default virtual host.

Enabling CGI scripts

Another problem to track down: CGI scripts had stopped working. I knew about Options +ExecCGI, but adding it wasn't helping. Turned out it also needed an AddHandler, which I don't remember having to add in recent versions on Ubuntu. I added this in the relevant virtual host file in sites-available:

  <Directory />
    AddHandler cgi-script .cgi
    Options ExecCGI

Enabling .htaccess

We have one enduring mystery: .htaccess files work without needing a line like AllowOverride FileInfo anywhere. I've needed to add that directive in Ubuntu-based apache2 installations, but Lenny seems to allow .htaccess without any override for it. I'm still not sure why it works. It's not supposed to. But hey, without a few mysteries, computers would be boring, right?

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[ 21:46 Jul 05, 2010    More tech/web | permalink to this entry | ]

Sun, 06 Sep 2009

Using apt-file to track down build errors

Someone was asking for help building XEphem on the XEphem mailing list. It was a simple case of a missing include file, where the only trick is to find out what package you need to install to get that file. (This is complicated on Ubuntu, which the poster was using, by the way they fragment the X developement headers into a maze of a xillion tiny packages.)

The solution -- apt-file -- is so simple and easy to use, and yet a lot of people don't know about it. So here's how it works.

The poster reported getting these compiler errors:

ar rc libz.a adler32.o compress.o crc32.o uncompr.o deflate.o trees.o zutil.o inflate.o inftrees.o inffast.o
ranlib libz.a
make[1]: Leaving directory `/home/gregs/xephem-3.7.4/libz'
gcc -I../../libastro -I../../libip -I../../liblilxml -I../../libjpegd -I../../libpng -I../../libz -g -O2 -Wall -I../../libXm/linux86 -I/usr/X11R6/include   -c -o aavso.o aavso.c
In file included from aavso.c:12:
../../libXm/linux86/Xm/Xm.h:56:27: error: X11/Intrinsic.h: No such file or directory
../../libXm/linux86/Xm/Xm.h:57:23: error: X11/Shell.h: No such file or directory
../../libXm/linux86/Xm/Xm.h:58:23: error: X11/Xatom.h: No such file or directory
../../libXm/linux86/Xm/Xm.h:59:34: error: X11/extensions/Print.h: No such file or directory
In file included from ../../libXm/linux86/Xm/Xm.h:60,
                 from aavso.c:12:
../../libXm/linux86/Xm/XmStrDefs.h:1373: error: expected `=', `,', `;', `asm' or `__attribute__' before `char'
In file included from ../../libXm/linux86/Xm/Xm.h:60,
                 from aavso.c:12:
../../libXm/linux86/Xm/XmStrDefs.h:5439:28: error: X11/StringDefs.h: No such file or directory
In file included from ../../libXm/linux86/Xm/Xm.h:61,
                 from aavso.c:12:
../../libXm/linux86/Xm/VirtKeys.h:108: error: expected `)' before `*' token
In file included from ../../libXm/linux86/Xm/Display.h:49,
                 from ../../libXm/linux86/Xm/DragC.h:48,
                 from ../../libXm/linux86/Xm/Transfer.h:44,
                 from ../../libXm/linux86/Xm/Xm.h:62,
                 from aavso.c:12:
../../libXm/linux86/Xm/DropSMgr.h:88: error: expected specifier-qualifier-list before `XEvent'
../../libXm/linux86/Xm/DropSMgr.h:100: error: expected specifier-qualifier-list before `XEvent'
How do you go about figuring this out?

When interpreting compiler errors, usually what matters is the *first* error. So try to find that. In the transcript above, the first line saying "error:" is this one:

../../libXm/linux86/Xm/Xm.h:56:27: error: X11/Intrinsic.h: No such file or directory

So the first problem is that the compiler is trying to find a file called Intrinsic.h that isn't installed.

On Debian-based systems, there's a great program you can use to find files available for install: apt-file. It's not installed by default, so install it, then update it, like this (the update will take a long time):

$ sudo apt-get install apt-file
$ sudo apt-file update
Once it's updated, you can now find out what package would install a file like this:
$  apt-file search Intrinsic.h
libxt-dev: /usr/include/X11/Intrinsic.h
tendra: /usr/lib/TenDRA/lib/include/x5/t.api/X11/Intrinsic.h

In this case two two packages could install a file by that name. You can usually figure out from looking which one is the "real" one (usually the one with the shorter name, or the one where the package name sounds related to what you're trying to do). If you're stil not sure, try something like apt-cache show libxt-dev tendra to find out more about the packages involved.

In this case, it's pretty clear that tendra is a red herring, and the problem is likely that the libxt-dev package is missing. So apt-get install libxt-dev and try the build again.

Repeat the process until you have everything you need for the build.

Remember apt-file if you're not already using it. It's tremendously useful in tracking down build dependencies.

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[ 11:25 Sep 06, 2009    More linux | permalink to this entry | ]

Sun, 01 Mar 2009

Simple pinning

"Pinning" is the usual way Debian derivatives (like Ubuntu) deal with pulling software from multiple releases. For instance, you need an updated gtk or qt library in order to build some program, but you don't want to pull in everything else from the newer release.

But most people, upon trying to actually set up pinning, get lost in the elaborate documentation and end up deciding maybe they don't really need it after all.

For years, I've been avoiding needing to learn pinning because of a wonderful LinuxChix Techtalk posting from Hamster years ago on easier method of pinning releases Basically, you add a line like:

APT::Default-Release "hardy";
to your /etc/apt/apt.conf (creating it if it doesn't already exist). Then when you need to pull something from the newer repository you pull with apt-get install -t hardy-backports packagename.

That's generally worked for me, until yesterday when I tried to pull a -dev package and found out it was incompatible with the library package I already had installed. It turned out that the lib package came from hardy-security, which is considered a different archive from hardy, so my Default-Release didn't apply to security updates (or bugfixes, which come from hardy-updates).

You can apparently only have one Default-Release. Since Ubuntu uses three different archives for hardy the only way to handle it is pinning. Pinning is documented in the man page apt_preferences(5) -- which is a perfect example of a well intentioned geek-written Unix man page. There's tons of information there -- someone went to a lot of work, bless their heart, to document exactly what happens and why, down to the algorithms used to decide priorities -- but straightforward "type X to achieve effect Y" examples are lost in the noise. If you want to figure out how to actually set this up on your own system, expect to spend a long time going back and forward and back and forward in the man page correlating bits from different sections.

Ubuntu guru Mackenzie Morgan was nice enough to help me out, and with her help I got the problem fixed pretty quickly. Here's the quick recipe:

First, remove the Default-Release thing from apt.conf.

Next, create /etc/apt/preferences and put this in it:

Package: *
Pin: release a=hardy-security
Pin-Priority: 950

Package: *
Pin: release a=hardy-updates
Pin-Priority: 940

Package: *
Pin: release a=hardy
Pin-Priority: 900

# Pin backports negative so it'll never try to auto-upgrade
Package: *
Pin: release a=hardy-backports
Pin-Priority: -1

Here's what it means:

a= means archive, though it's apparently not really needed.

The hardy-security archive has the highest priority, 950. hardy-updates is right behind it with 940 (actually, setting these equal might be smarter but I'm not sure it matters).

hardy, which apparently is just the software initially installed, is lower priority so it won't override the other two.

Finally, hardy-backports has a negative priority so that apt will never try to upgrade automatically from it; it'll only grab things from there if I specify apt-get install -t hardy-backports.

You can put comments (with #) in /etc/apt/preferences but not in apt.conf -- they're a syntax error there (so don't bother trying to comment out that Default-Release line).

And while you're editing apt.conf, a useful thing to put there is:

APT::Install-Recommends "false";
APT::Install-Suggests "false";
which prevents apt from automatically installing recommended or suggested packages. Aptitude will still install the recommends and suggests; it's supposed to be configurable in aptitude as well, but turning it off never worked for me, so mostly I just stick to apt-get.

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[ 21:19 Mar 01, 2009    More linux/install | permalink to this entry | ]

Tue, 13 Jan 2009

Debian/Ubuntu repositories for Pho

I've been wanting for a long time to make Debian and Ubuntu repositories so people can install pho with apt-get, but every time I try to look it up I get bogged down.

But I got mail from a pho user who really wanted that, and even suggested a howto. That howto didn't quite do it, but it got me moving to look for a better one, which I eventually found in the Debian Repository Howto.

It wasn't complete either, alas, so it took some trial-and-error before it actually worked. Here's what finally worked:

I created two web-accessible directories, called hardy and etch. I copied all the files created by dpgk-buildpkg on each distro -- .deb, .dsc, .tar.gz, and .changes (I don't think this last file is used by anything) -- into each directory (renaming them to add -etch and -hardy as appropriate). Then:

% cd hardy/
% dpkg-scanpackages . /dev/null | gzip > Packages.gz
% dpkg-scansources . /dev/null | gzip > Sources.gz
% cd ../etch/
% dpkg-scanpackages . /dev/null | gzip > Packages.gz
% dpkg-scansources . /dev/null | gzip > Sources.gz
It gives an error,
** Packages in archive but missing from override file: **
but seems to work anyway.

Now you can use one of the following /etc/apt/sources.list lines:
deb ./
deb ./

After an apt-get update, it saw pho, but it warned me

WARNING: The following packages cannot be authenticated!
Install these packages without verification [y/N]?
There's some discussion in the SecureAPT page on the Debian wiki, but it's a bit involved and I'm not clear if it helps me if I'm not already part of the official Debian keychain.

This page on Release check of non Debian sources was a little more helpful, and told me how to create the Release and Release.gpg file -- but then I just get a different error,

 The following signatures couldn't be verified because the public key is not available: NO_PUBKEY
And worse, it's an error now, not just a warning, preventing any apt-get update.

Going back to the SecureApt page, under Setting up a secure apt repository they give the two steps the other page gave for creating Release and Release.gpg, with a third step: "Publish the key fingerprint, that way your users will know what key they need to import in order to authenticate the files in the archive."

So apparently if users don't take steps to import the key manually, they can't update at all. Whereas if I leave out the Release and Release.gpg files, all they have to do is type y when they see the warning. Sounds like it's better to leave off the key. I wish, though, that there was a middle ground, where I could offer the key for those who wanted it without making it harder for those who don't care.

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[ 21:14 Jan 13, 2009    More linux | permalink to this entry | ]

Fri, 16 May 2008

How to set your time zone

My laptop's clock has been drifting. I suspect the clock battery is low (not surprising on a 7-year-old machine). But after an hour of poking and prodding, I've been unable to find a way to expose the circuit board under the keyboard, either from the top (keyboard) side -- though I know how to remove individual keycaps, thanks to a reader who sent me detailed instructions a while back (thanks, Miles!) -- or the bottom. Any expert on Vaio SR laptops know how this works?

Anyway, that means I have to check and reset the time periodically. So this morning I did a time check and found it many hours off. No, wait -- actually it was pretty close; it only looked like it was way off because the system had suddenly decided it was in UTC, not PDT. But how could I change that back?

I checked /etc/timezone -- sure enough, it was set to UTC. So I changed that, copying one from a debian machine -- "US/Pacific", but that didn't do it, even after a reboot.

I spent some time reading man hwclock -- there's a lot of good reading in that manual page, about the relation between the system (kernel) clock and the hardware clock. Did you know that you're not supposed to use the date command to set the system time while the system is running? Me neither -- I do that all the time. Hmm. Anyway, interesting reading, but nothing useful about the system time zone.

It has an extensive SEE ALSO list at the end, so I explored some of those documents. /usr/share/doc/util-linux/README.Debian.hwclock is full of lots of interesting information, well worth reading, but it didn't have the answer. man tzset sounded promising, but there was no such man page (or program) on my system. Just for the heckofit, I tried typing tz[tab] to see if I had any other timezone-related programs installed ... and found tzselect. And there was the answer, added almost as an afterthought at the end of the manual page:

Note that tzselect will not actually change the timezone for you. Use 'dpkg-reconfigure tzdata' to achieve this.
Sure enough, dpkg-reconfigure tzdata let me set the time zone. And it even seems to be remembered through a reboot.

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[ 11:04 May 16, 2008    More linux | permalink to this entry | ]

Sun, 20 Apr 2008

Upgrading from Ubuntu Gutsy to Hardy

I finally had a moment to upgrade my desktop to Ubuntu's "Hardy Heron". I followed the same procedure as when I went from feisty to gutsy:
  1. cp -ax / /hardy
  2. cp -ax /dev/.static/dev/* /hardy/dev/
  3. Fix up files like /hardy/etc/fstab and /boot/grub/menu.lst
  4. Reboot into the newly copied gutsy
  5. do-release-upgrade -d

It took an hour or two to pull down all the files, followed by a long interval of occasionally typing Y or N, and then I was ready to start cleaning up some of the packages I'd noticed flying by that I didn't want. Oops! I couldn't remove or install anything with apt-get, because: dpkg --configure -a
But I couldn't dpkg --configure -a because several packages were broken.

The first broken package was plucker, which apparently had failed to install any files. Its postinstall script was failing because it had no files to operate on; and then I couldn't do anything further with it because apt-get wouldn't do anything until I did a dpkg --reconfigure -a

I finally got out of that by dpkg -P plucker; then after several more dpkg --reconfigure -a rounds I was eventually able to apt-get install plucker (which installed just fine the second time).

But apt still wasn't happy, because it wanted to run the trigger for initramfs-tools, which wouldn't run because it wanted kernel modules for some specific kernel version in /lib/modules. I didn't have any kernel modules because I'm not running Ubuntu's kernel (I'm stuck on 2.6.23 because bug 10118 makes all 2.6.24 variants unable to sync with USB Palm devices). But I couldn't remove initramfs-tools because udev (along with a bunch of other less important packages) depends on it. I finally found my way out of that by removing /var/lib/dpkg/triggers/initramfs-tools. I reported it as bug 220094.

Update: I forgot to mention one important thing I hit both on this machine and earlier, on the laptop: /usr/bin/play (provided by the "sox" package) no longer works because it now depends on a zillion separate libraries. apt-get install libsox-fmt-all to get all of them.

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[ 21:02 Apr 20, 2008    More linux/install | permalink to this entry | ]

Sun, 06 Apr 2008


Some time ago, I wished for a simple Linux "Tarball installer", something that could install a minimal install of a Linux distribution onto an existing partition or directory, skipping all the flaky and error-prone hardware-guessing that installers do.

It turns out Debian (and therefore also Ubuntu) has had this for years, and it's totally cool. It's called debootstrap.

Some folks on the #ubuntu+1 channel told me about it, and I found a nice clear howto article on how to use it for Debian. It works just the same for Ubuntu.

First, get the .deb package for the debootstrap you want to use. Here's debootstrap for Ubuntu Hardy Heron. Install it with dpkg -i. Then run it, giving it the name of the system you want to install and the directory (or mounted partition) where you want to install it. Like this: debootstrap hardy /mnt/hda3

That's all! It fetches the files it needs from the online repositories. It takes no time at all -- this really is a minimal system.

Then you need to do some fiddling to turn it into a bootable system. That includes (all paths relative to the newly installed filesystem unless otherwise stated):

Now you're read to reboot into the new system. Of course, since this is a very minimal system, you have a lot more work to do. Hardly anything is installed, and nothing has been configured for you. Some things may be challenging (for example, as I write this, X is installed but most of the fonts aren't showing up properly, which may be a bug in Hardy).

Anyway, you can get a good start by mounting your old system's root directory and copying some starter files from there, starting with these:

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[ 13:54 Apr 06, 2008    More linux/install | permalink to this entry | ]

Sat, 18 Aug 2007

The Importance of Being ESSID (simple Linux wi-fi troubleshooting)

I'm forever having problems connecting to wireless networks, especially with my Netgear Prism 54 card. The most common failure mode: I insert the card and run /etc/init.d/networking restart (udev is supposed to handle this, but that stopped working a month or so ago). The card looks like it's connecting, ifconfig eth0 says it has the right IP address and it's marked up -- but try to connect anywhere and it says "no route to host" or "Destination host unreachable".

I've seen this both on networks which require a WEP key and those that don't, and on nets where my older Prism2/Orinoco based card will connect fine.

Apparently, the root of the problem is that the Prism54 is more sensitive than the Prism2: it can see more nearby networks. The Prism2 (with the orinoco_cs driver) only sees the strongest network, and gloms onto it. But the Prism54 chooses an access point according to arcane wisdom only known to the driver developers. So even if you're sitting right next to your access point and the next one is half a block away and almost out of range, you need to specify which one you want. How do you do that? Use the ESSID.

Every wireless network has a short identifier called the ESSID to distinguish it from other nearby networks. You can list all the access points the card sees with:

iwlist eth0 scan
(I'll be assuming eth0 as the ethernet device throughout this article. Depending on your distro and hardware, you may need to substitute ath0 or eth1 or whatever your wireless card calls itself. Some cards don't support scanning, but details like that seem to be improving in recent kernels.)

You'll probably see a lot of ESSIDs like "linksys" or "default" or "OEM" -- the default values on typical low-cost consumer access points. Of course, you can set your own access point's ESSID to anything you want.

So what if you think your wireless card should be working, but it can't connect anywhere? Check the ESSID first. Start with iwconfig:

iwconfig eth0
iwconfig lists the access point associated with the card right now. If it's not the one you expect, there are two ways to change that.

First, change it temporarily to make sure you're choosing the right ESSID:

iwconfig eth0 essid MyESSID

If your accesspoint requires a key, add key nnnnnnnnnn to the end of that line. Then see if your network is working.

If that works, you can make it permanent. On Debian-derived distros, just add lines to the entry in /etc/network/interfaces:

wireless-essid MyESSID
wireless-key nnnnnnnnnn

Some older howtos may suggest an interfaces line that looks like this:
up iwconfig eth0 essid MyESSID
Don't get sucked in. This "up" syntax used to work (along with pre-up and post-up), but although man interfaces still mentions it, it doesn't work reliably in modern releases. Use wireless-essid instead.

Of course, you can also use a gooey tool like gnome-network-manager to set the essid and key. Not being a gnome user, some time ago I hacked up the beginnings of a standalone Python GTK tool to configure networks. During this week's wi-fi fiddlings, I dug it out and blew some of the dust off: wifi-picker.

You can choose from a list of known networks (including both essid and key) set up in your own configuration file, or from a list of essids currently visible to the card, and (assuming you run it as root) it can then set the essid and key to whatever you choose. For networks I use often, I prefer to set up a long-term network scheme, but it's fun to have something I can run once to show me the visible networks then let me set essid and key.

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[ 15:44 Aug 18, 2007    More linux | permalink to this entry | ]

Tue, 15 May 2007

Etch: Blacklisting Modules, Udev, and Firewire Networking

The new Debian Etch installation on my laptop was working pretty well. But it had one weirdness: the ethernet card was on eth1, not eth0. ifconfig -a revealed that eth0 was ... something else, with no IP address configured and a really long MAC address. What was it?

Poking around dmesg revealed that it was related to the IEEE 1394 and the eth1394 module. It was firewire networking.

This laptop, being a Vaio, does have a built-in firewire interface (Sony calls it i.Link). The Etch installer, when it detected no network present, had noted that it was "possible, though unlikely" that I might want to use firewire instead, and asked whether to enable it. I declined.

Yet the installed system ended up with firewire networking not only installed, but taking the first network slot, ahead of any network cards. It didn't get in the way of functionality, but it was annoying and clutters the output whenever I type ifconfig -a. Probably took up a little extra boot time and system resources, too. I wanted it gone.

Easier said than done, as it turns out.

I could see two possible approaches.

  1. Figure out who was setting it to eth1, and tell it to ignore the device instead.
  2. Blacklist the kernel module, so it couldn't load at all.

I begain with approach 1. The obvious culprit, of course, was udev. (I had already ruled out hal, by removing it, rebooting and observing that the bogus eth0 was still there.) Poking around /etc/udev/rules.d revealed the file where the naming was happening: z25_persistent-net.rules.

It looks like all you have to do is comment out the two lines for the firewire device in that file. Don't believe it. Upon reboot, udev sees the firewire devices and says "Oops! persistent-net.rules doesn't have a rule for this device. I'd better add one!" and you end up with both your commented-out line, plus a brand new uncommented line. No help.

Where is that controlled? From another file, z45_persistent-net-generator.rules. So all you have to do is edit that file and comment out the lines, right?

Well, no. The firewire lines in that file merely tell udev how to add a comment when it updates z25_persistent-net.rules. It still updates the file, it just doesn't comment it as clearly.

There are some lines in z45_persistent-net-generator.rules whose comments say they're disabling particular devices, by adding a rule GOTO="persistent_net_generator_end". But adding that in the firewire device lines caused the boot process to hang. There may be a way to ignore a device from this file, but I haven't found it, nor any documentation on how this system works.

Defeated, I switched to approach 2: prevent the module from loading at all. I never expect to use firewire networking, so it's no loss. And indeed, there are lots of other modules loaded I'd like to blacklist, since they represent hardware this machine doesn't have. So it would be nice to learn how.

I had a vague memory of there having been a file with a name like /etc/modules.blacklist some time back in the Pliocene. But apparently no such file exists any more. I did find /etc/modprobe.d/blacklist, which looked promising; but the comment at the beginning of that file says

# This file lists modules which will not be loaded as the result of
# alias expsnsion, with the purpose of preventing the hotplug subsystem
# to load them. It does not affect autoloading of modules by the kernel.
Okay, sounds like this file isn't what I wanted. (And ... hotplug? I thought that was long gone, replaced by udev scripts.) I tried it anyway. Sure enough, not what I wanted.

I fiddled with several other approaches before Debian diva Erinn Clark found this helpful page. I created a file called /etc/modprobe.d/00local and added this line to it:

install eth1394 /bin/true
and on the next boot, the module was no longer loaded, and no longer showed up as a bogus ethernet device. Hurray!

This /etc/modprobe.d/00local technique probably doesn't bear examining too closely. It has "hack" written all over it. But if that's the only way to blacklist problematic modules, I guess it's better than nothing.

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[ 19:10 May 15, 2007    More linux | permalink to this entry | ]

Debian "Etch": a Sketch

Since I'd already tried the latest Ubuntu on my desktop, I wanted to check out Debian's latest, "Etch", on my laptop.

The installer was the same as always, and the same as the Ubuntu installer. No surprises, although I do like the way Debian gives me a choice of system types to install (Basic desktop, Web server, etc. ... though why isn't "Development" an option?) compared to Ubuntu's "take the packages we give you and deal with it later" approach.

Otherwise, the install went very much like a typical Ubuntu install. I followed the usual procedures and workarounds so as not to overwrite the existing grub, to get around the Vaio hardware issues, etc. No big deal, and the install went smoothly.

The good

But the real surprise came on booting into the new system. Background: my Vaio SR-17 has a quirk (which regular readers will have heard about already): it has one PCMCIA slot, which is needed for either the external CDROM drive or a network card. This means that at any one time, you can have a network, or a CDROM, but not both. This tends to throw Debian-based installers into a tizzy -- you have to go through five or more screens (including timing out on DHCP even after you've told it that you have no network card) to persuade the installer that yes, you really don't have a network and it's okay to continue anyway.

That means that the first step after rebooting into the new system is always configuring the network card. In Ubuntu installs, this typically means either fiddling endlessly with entries in the System or Admin menus, or editing /etc/network/interfaces.

Anticipating a vi session, I booted into my new Etch and inserted the network card (a 3COM 3c59x which often confuses Ubuntu). Immediately, something began spinning in the upper taskbar. Curious, I waited, and in ten seconds or so a popup appeared informing me "You are now connected to the wired net."

And indeed I was! The network worked fine. Kudos to debian -- Etch is the first distro which has ever handled this automatically. (I still need to edit /etc/network/interfaces to set my static IP address -- network manager

Of course, since this was my laptop, the next most important feature is power management. Happily, both sleep and hibernate worked correctly, once I installed the hibernate package. That had been my biggest worry: Ubuntu was an early pioneer in getting ACPI and power management code working properly, but it looks like Debian has caught up.

The bad

I did see a couple of minor glitches.

First, I got a lot of system hangs in X. These turned out to be the usual dri problem on S3 video cards. It's a well known bug, and I wish distros would fix it!

I've also gotten at least one kernel OOPS, but I have a theory about what might be causing that. Time will tell whether it's a real problem.

It took a little googling to figure out the line I needed to add to /etc/apt/sources.list in order to install programs that weren't included on the CD. (Etch automatically adds lines for security updates, but not for getting new software). But fortunately, lots of other people have already asked this in a variety of forums. The answer is:

deb etch main contrib non-free

My husband had suggested that Etch might be lighter weight than Ubuntu and less dependent on hal (which I always remove from my laptop, because its constant hardware polling makes noise and sucks power). But no: Etch installed hal, and any attempt to uninstall it takes with it the whole gnome desktop environment, plus network-manager (that's apparently that nice app that noticed my network card earlier) and rhythmbox. I don't actually use the gnome desktop or these other programs, but it would be nice to have the option of trying them when I want to check something out. So for now I've resorted to the temporary solution: mv /usr/sbin/hald /usr/sbin/hald-not

The ugly

Etch looks fairly nice, and I'm looking forward to exploring it. I'm mostly kidding about the "ugly". I did hit one minor bit of ugliness involving network devices which led me on a two-hour chase ... but I'll save that for its own article.

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[ 14:29 May 15, 2007    More linux | permalink to this entry | ]

Wed, 14 Mar 2007

The Various Debian Upgrade Methods

Carla Schroder's latest (excellent) article, Cheatsheet: Master Linux Package Management, spawned a LinuxChix discussion of the subtleties of Debian package management (which includes other Debian-based distros such as Ubuntu, Knoppix etc.) Specifically, we were unclear on the differences among apt-get upgrade or dist-upgrade, aptitude upgrade, aptitude dist-upgrade, and aptitude -f dist-upgrade. Most of us have just been typing whichever command we learned first, without understanding the trade-offs.

But Erinn Clark, our Debian Diva, checked with some of her fellow Debian experts and got us most of the answers, which I will attempt to summarize with a little extra help from web references and man pages.

First, apt-get vs. aptitude: we were told that the primary difference between them is that "aptitude is less likely to remove packages." I confess I'm still not entirely clear on what that means, but aptitude is seen as safer and smarter and I'll go on using it.

aptitude upgrade gets updates (security, bug fixes or whatever) to all currently installed packages. No packages will be removed, and no new packages will be installed. If a currently installed package changes to require a new package that isn't installed, upgrade will refuse to update those packages (they will be "kept back"). To install the "kept back" packages with their dependencies, you can use:

aptitude dist-upgrade gets updates to the currently installed packages, including any new packages which are now required. But sometimes you'll encounter problems in the dependencies, in which case it will suggest that you:

aptitude -f dist-upgrade tries to "fix broken packages", packages with broken dependencies. What sort of broken dependencies? Well, for example, if one of the new packages conflicts with another installed package, it will offer to remove the conflicting package. Without -f, all you get is that a package will be "held back" for unspecified reasons, and you have to go probing with commands like aptitude -u install pkgname or apt-get -o Debug::pkgProblemResolver=yes dist-upgrade to find out the reason.

The upshot is that if you want everything to just happen in one step without pestering you, use aptitude -f dist-upgrade; if you want to be cautious and think things through at each step, use aptitude upgrade and be willing to type the stronger commands when it runs into trouble.

Sections 6.2 and 6.3 of the Debian Reference cover these commands a little, but not in much detail. The APT Howto is better, and runs through some useful examples (which I used to try to understand what -f does).

Thanks go to Erinn, Ari Pollak, and Martin Krafft (whose highly rated book, The Debian System: Concepts and Techniques, apparently would have answered these questions, and I'll be checking it out).

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[ 22:19 Mar 14, 2007    More linux | permalink to this entry | ]

Fri, 18 Nov 2005

(Really) Reinstalling on Debian

I found myself in a situation where a package was mostly installed, but it was missing some files, notably the startup file in /etc/init.d/packagename. No problem, right? Just reinstall the package.

Well, no. dpkg -i packagename spun and looked busy for a while, but the missing file didn't appear. Removing the package first with dpkg -r packagename, then reinstalling, didn't help either, nor did dpkg -i --force-newconfig packagename. (I didn't try dpkg -r --purge packagename because I already had invested some time into setting up the files in the package and was hoping to avoid losing that work.)

Of course, I could have extracted the .deb somewhere else and pulled the single init.d file out of it; but I was worried that I might be missing other files, and end up with a flaky package.

Well, as far as I can tell, there really isn't any way to do this "right" in Debian: there's no way to tell dpkg "Really install this package, every file in it, even if you think maybe some of the files already got installed before", or "Install any file in this package which doesn't currently exist on disk." It's amazing (I'm pretty sure RPM offered both of these options) but apparently this isn't something dpkg allows.

I found a way to trick it, though:

rm /var/lib/dpkg/info/packagename.*
dpkg -i packagename

You get a lovely warning that
dpkg: serious warning: files list file for package `packagename' missing, assuming package has no files currently installed.
and then dpkg finally goes ahead and reinstalls all the files. Whew!

Update: Aha! It is possible after all. dpkg i --force-confmiss is the option I wasn't seeing. Thanks, Yosh!

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[ 19:01 Nov 18, 2005    More linux | permalink to this entry | ]

Tue, 12 Apr 2005

New Debian Font Weirdness

A recent change to the Debian font system has caused some odd font problems which Debian users might do well to know about.

The change has to do with the addition in /etc/fonts of a directory conf.d containing symbolic links to scripts, and the overwriting of some of the existing files in /etc/fonts.

The symptoms are varied and peculiar. On my sid system, on each boot, the system would toggle between two different font resolutions. I'd start xchat, and the fonts would be too teeny to read; so I'd call up the preferences dialog, see the font was at 9, and increase it to 12, at which point I'd see the font I was used to seeing (though the UI font in the tabs would still be teeny). Subsequent runs of xchat would be fine (except for the still-teeny tab fonts). But upon reboot, xchat would come up with the tab font correct and the channel font HUGE. Prefs dialog again: it's still at 12 where I set it last time, so now I reset it to 9, which makes it the right size. Until the next reboot, when everything became teeny again and I have to go back to 12.

The system resolution never changed, nor did the rendering of the bitmapped fonts I use in emacs and terminal clients; only the rendering of freetype scalable fonts changed with each reboot. Back in the days when all fonts were bitmapped, I would have guessed that the font system was alternating between 100dpi fonts and 72dpi fonts.

At a loss as to what might cause this strange behavior, I took a peek into /etc/fonts/conf.d, which Dave had discovered a few weeks ago when he updated his sarge system and all his bitmapped fonts disappeared. Though my problem didn't sound remotely similar to his: my bitmapped fonts were fine, it was the scalable ones which were flaky.

Turns out the symlink I'd aquired in the update, /etc/fonts/conf.d/30-debconf-no-bitmaps.conf, did indeed point to a file called no-bitmaps.conf, just as Dave's had. Just to see what would happen, I removed it, and made a new symlink, 30-debconf-yes-bitmaps.conf, pointing to yes-bitmaps.conf.

Voila! The size-toggling problem disappeared, and, even better, bitmapped fonts like "clean" now show up in gtkfontsel and in gtk font selection dialogs, which they never did before. I can use all my fonts now!

The moral is: if you've updated sarge or sid recently, and see any weirdness at all in fonts, go to /etc/fonts/conf.d and fiddle with the symlinks. Even if it doesn't seem directly related to your problem.

As to why no-bitmaps.conf causes the system to toggle between two different font scalings, that's still a mystery. The only difference between no-bitmaps.conf and yes-bitmaps.conf is that one rejects, and the other accepts, fonts that have "scalable" set to false. Why that would change the scale at which fonts are rendered is beyond me. I'll leave that up to someone who understands the new debian font system. If any such person exists.

Update 5/24/2005: turns out you can change this on a per-user basis too, with ~/.fonts.conf. man fonts.conf for details.

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[ 22:45 Apr 12, 2005    More linux | permalink to this entry | ]

Wed, 02 Mar 2005

Debian Networking and Hotplug Update; 2.6 Instability

I like to keep my laptop's boot sequence lean and mean, so it can boot very quickly. (Eventually I'll write about this in more detail.) Recently I made some tweaks, and then went through a couple of dist-upgrades (it's currently running Debian "sarge"), and had some glitches. Some of what I learned was interesting enough to be worth sharing.

First, apache stopped serving http://localhost/ -- not important for most machines, but on the laptop it's nice to be able to use a local web server when there's no network connected. Further investigation revealed that this had nothing to do with apache: it was localhost that wasn't working, for any port. I thought perhaps my recent install of 2.4.29 was at fault, since some configuration had changed, but that wasn't it either. Eventually I discovered that the lo interface was there, but wasn't being configured, because my boot-time tweaking had disabled the ifupdown boot-time script, normally called from /etc/rcS.d.

That's all straightforward, and I restored ifupdown to its rightful place using update-rc.d ifupdown start 39 S .
Dancer suggested apt-get install --reinstall ifupdown which sounds like a better way; I'll do that next time. But meanwhile, what's this ifupdown-clean script that gets installed as S18ifupdown-clean ?

I asked around, but nobody seemed to know, and googling doesn't make it any clearer. The script obviously cleans up something related to /etc/network/ifstate, which seems to be a text file holding the names of the currently configured network interfaces. Why? Wouldn't it be better to get this information from the kernel or from ifconfig? I remain unclear as to what the ifstate file is for or why ifupdown-clean is needed.

Now my loopback interface worked -- hurray!

But after another dist-upgrade, now eth0 stopped working. It turns out there's a new hotplug in town. (I knew this because apt-get asked me for permission to overwrite /etc/hotplug/net.agent; the changes were significant enough that I said yes, fully aware that this would likely break eth0.) The new net.agent comes with comments referencing NET_AGENT_POLICY in /etc/default/hotplug, and documentation in /usr/share/doc/hotplug/README.Debian. I found the documentation baffling -- did NET_AGENT_POLICY=all mean that it would try to configure all interfaces on boot, or only that it would try to configure them when they were hotplugged?

It turns out it means the latter. net.agent defaults to NET_AGENT_POLICY=hotplug, which doesn't do anything unless you edit /etc/network/interfaces and make a bunch of changes; but changing NET_AGENT_POLICY=all makes hotplug "just work". I didn't even have to excise LIFACE from the net.agent code, like I needed to in the previous release. And it still works fine with all my existing Network Schemes entries in /etc/network/interfaces.

This new hotplug looks like a win for laptop users. I haven't tried it with usb yet, but I have no reason to worry about that.

Speaking of usb, hotplug, and the laptop: I'm forever hoping to switch to the 2.6 kernel, because it handles usb hotplug so much better than 2.4; but so far, I've been prevented by PCMCIA hotplug issues and general instability when the laptop suspends and resumes. (2.6 works fine on the desktop, where PCMCIA and power management don't come into play.)

A few days ago, I built both 2.4.29 and 2.6.10, since I was behind on both branches. 2.4.29 works fine. 2.6.10, alas, is even less stable than 2.6.9 was. On the laptop's very first resume from BIOS suspend after the first 2.6.10 boot, it hung, in the same way I'd been seeing sporadically from 2.6.9: no keyboard lights blinking (so not a kernel "oops"), cpu fan sometimes spinning, and no keyboard response to ctl-alt-Fn or anything else. I suppose the next step is to hook up the "magic sysrq" key and see if it responds to the keyboard at all when in that state.

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[ 23:06 Mar 02, 2005    More linux | permalink to this entry | ]

Mon, 20 Dec 2004

Giving Up On Debian -- It Damages My Printer!

I've forever struggled with Debian's printing system. A few months ago, Debian unstable introduced a new package called printconf which, once I discovered by accident it required the parallel port to be in EPP mode, actually detected and configured my trusty Epson Photo 700. It was a happy day!

But since then, the printing system has broken again. It wasn't so bad when printing did nothing at all, or printed random garbage characters or postscript instead of a picture. But now (for the past month or so), what it does is print out a centimeter or so of reasonable graphics, after which the printer starts to issue horrible grinding noises and has to be powered off in order to stop the destruction.

I discovered through much fiddling that I could get the printer working again (on a non-Debian system) by powering it off and leaving it that way for quite a while (a few minutes doesn't seem to be enough, but 20 minutes is), then plugging it into the SuSE 9.1 machine and running a series of clean/nozzle test/clean cycles. Eventually, after the second round where the nozzle test prints clean, the printer works normally again from SuSE or Redhat. I still don't know whether all that loud grinding is doing any permanent damage to the printer.

I suspect the actual problem may be something like paper size. In the few months during which printing actually worked, I had lots of problems with mozilla's printouts overrunning the page, which turned out to be due to Xprint having its own idea of paper size (A4) rather than following the system setting (usletter). I never did find a place to configure Xprint's idea of paper size, so I uninstalled Xprint, and mozilla magically became able to print on usletter paper. But it's possible there are other parameters buried in the debian printing system somewhere, perhaps telling the printer to print to paper wider than it's capable of.

I've filed bugs, but they never get any response which might offer a clue how I could help debug this; I suspect Debian's print spooling system is basically orphaned. I've tried installing and uninstalling every combination of the myriad print spooling components I can find. I'd love to uninstall it all and build the whole spooler from source, and then perhaps try to track down the problem and fix it, but there are so many pieces which all work together in undocumented ways that I don't know where to start. (Perhaps by installing exactly the component set that SuSE does?)

I'm reluctantly giving up on Debian for my primary desktop machine. I like almost everything else about Debian, and I've run it for several years on my primary machine; but during that time I've only had a few months here and there where printing briefly worked before breaking again. There must be a distro that can do easy software updates like Debian, yet is still capable of driving a printer without damaging it!

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[ 23:46 Dec 20, 2004    More linux | permalink to this entry | ]

Fri, 05 Nov 2004

Little successes (printing on Debian)

Printing's been broken on my Debian machine forever. For one brief shining moment back in July I briefly got it working, then a week later a dist-upgrade broke it again and it's been broken ever since.

Last week Debian Weekly News mentioned a new package called "printconf" which supposedly autoconfigures usb and parallel printers for CUPS. Now, setting aside for the moment that there's already a package called printconf, which configures a completely different spooler than CUPS, and that it's very confusing of Debian to resurrect an old name for a completely different purpose, of course I wanted to try it.

At apt-get time, it asked me whether I wanted to configure my printers now, and of course I said yes. The package installed, it printed a message about restarting CUPS, and no more details. Did it do anything?

I visited the CUPS configuration url (CUPS is configured via a web browser) and the entry looked like my old printer entry. Just for ducks I clicked "print a test page". Nada. So I removed the entry, went back to my root shell and typed printconf. It printed "Restarting cups ... done." No other info. Back to the web configuration page ... no printer there.

Eventually I discovered the -v option, which at least told me that it wasn't finding any parallel printers. I know this printer can be detected via the parallel port (SuSE and Mandrake both autoconfigure it), so something was wrong. Time to look at the BIOS.

A bunch of reboots later, I finally managed to get into my machine's BIOS screen (hint: repeatedly press DEL during boot. The screen saying DEL is the right key only flashes for a fraction of a second, so there's no hope of ever reading it and I wasted several boot cycles pressing function keys instead) and changed the parallel port from "ECP" to "ECP/EPP". Back into Debian -- and voila! printconf saw the printer, autoconfigured it with some magic the earlier entry hadn't had, and after a year and a half I have a debian printer again!

(Incidentally, the parallel port setting isn't why the printer wasn't working before; it was something about the CUPS configuration. Printing used to work on this machine several years ago and the BIOS settings haven't changed since then.)

All hail printconf! I wonder if it's ever occurred to anyone to mention in the man page that it needs an EPP (or ECP/EPP?) parallel port?

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[ 22:05 Nov 05, 2004    More linux | permalink to this entry | ]

Sat, 31 Jul 2004

Got the external mouse working again

For some reason X on the laptop hasn't been seeing the external USB mouse. But last night I got it working again. Turns out that /dev/input/mouse0 no longer works; I have to use /dev/input/mice because the mouse number changes each time it's plugged in (which I don't think was a problem with earlier kernels). Thanks to Peter S. for helping me track the problem down.

I also learned (unrelated to the mouse issue) about a couple of very useful Debian apps, deborphan and debfoster, for finding orphaned and no longer needed libraries. I'd always wanted something like that to help clean up my crufty debian systems.

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[ 19:39 Jul 31, 2004    More linux | permalink to this entry | ]

Tue, 20 Jul 2004

Printing working on debian, at last

After a year of no printing on sid, I went back to sarge to see if I could still print from there.

When I dist-upgraded my ancient sarge, one of the questions it asked me was whether to replace printers.conf. That sounded suspicious: I saved the old printers.conf, then allowed it to replace it with its new version.

Well, sure enough, with the new printers.conf it didn't know about my Epson, and when I went to the cups admin url to add it, there was no "add printer" button. Just like I'd always seen in sid.

In sid, someone once gave me the direct url to "add a printer", but when I followed it, I didn't get a working setup anyway. I decided to try copying my old printers.conf on top of the new one.

And voila, it worked! Printing works okay from sarge. (It still has the problem of the cups test page outlines not aligning well with the physical printer page, so it may not work for printing labels, but it's a start.)

So I moved over to sid, and tried the same printers.conf. Voila, something came out of the printer, the first I've ever seen that happen from sid! It didn't entirely work: I printed a few lines using lpr, and the printer printed those lines but then didn't eject the page, and I had to wrestle with the printer to get the paper out. So all is not quite well in sid land, but it's much farther along than it was using only the tools available in sid (rather than my two-year-old printers.conf originally configured on a much older sarge).

The other interesting file that upgrade asked me about was epson.conf, which turns out to be for the epson scanner, not the epson printer. Perhaps by using that (I saved the old sarge file) I'll eventually be able to get scanning working on sid! That would be lovely. For now, I'm using sarge a lot more.

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[ 23:09 Jul 20, 2004    More linux | permalink to this entry | ]

Wed, 07 Jul 2004

DRI works after all

Got an account on alioth, akkana-guest.

Discovered that the tuxracer problem I've been having isn't actually Debian sid having broken DRI, but merely some problem with the commercial tuxracer (probably not loading the gl libs properly or something). Free tuxracer still works. Yay.

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[ 20:00 Jul 07, 2004    More linux | permalink to this entry | ]