Shallow Thoughts : tags : grub

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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Tags: linux, debian, ubuntu, grub, boot
[ 19:29 Jan 17, 2022    More linux | permalink to this entry | ]

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.

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Tags: linux, boot, grub, debian, ubuntu
[ 19:53 Dec 28, 2021    More linux | permalink to this entry | ]

Making an Ubuntu live USB stick persistent

I wrote a few days ago about my multi-distro Linux live USB stick. Very handy!

But one thing that bugs me about live distros: they're set up with default settings and don't have a lot of the programs I want to use. Even getting a terminal takes quite a lot of clicks on most distros. If only they would save their settings!

It's possible to make a live USB stick "persistent", but not much is written about it. Most of what's written tells you to create the USB stick with usb-creator -- a GUI app that I've tried periodically for the past two years without ever once succeeding in creating a bootable USB stick.

Even if usb-creator did work, it wouldn't work with a multi-boot stick like this one, because it would want to overwrite the whole drive. So how does persistence really work? What is usb-creator doing, anyway?

How persistence works: Casper

The best howto I've found on Ubuntu persistence is LiveCD Persistence. But it's long and you have to wade through a lot of fdisk commands and similar arcana. So here's how to take your multi-distro stick and make at least one of the installs persistent.

Ubuntu persistence uses a package called casper which overlays the live filesystem with the contents of another filesystem. Figuring out where it looks for that filesystem is the key.

Casper looks for its persistent storage in two possible places: a partition with the label "casper-rw", and a file named "casper-rw" at the root of its mounted partitions.

So you could make a separate partition labeled "casper-rw", using your favorite partitioning tool, such as gparted or fdisk. But if you already have your multi-distro stick set up as one big partition, it's just as easy to create a file. You'll have to decide how big to make the file, based on the size of your USB stick.

I'm using a 4G stick, and I chose 512M for my persistent partition:

$ dd if=/dev/zero of=/path/to/casper-rw bs=1M count=512

Be patient: this step takes a while.

Next, create a filesystem inside that file. I'm not sure what the tradeoffs are among various filesystem types -- no filesystem is optimized for being run as a loopback file read from a vfat USB stick that was also the boot device. So I flipped a coin and used ext3:

$ mkfs.ext3 /path/to/casper-rw
/path/to/casper-rw is not a block special device.
Proceed anyway? (y,n) y

One more step: you need to add the persistent flag to your boot options. If you're following the multi-distro USB stick tutorial I linked to earlier, that means you should edit boot/grub/grub.cfg on the USB stick, find the boot stanza you're using for Ubuntu, and make the line starting with linux look something like this:

    linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet splash noprompt persistent --

Now write the stick, unmount it, and try booting your live install.

Testing: did it work?

The LiveCD/Persistence page says persistent settings aren't necessarily saved for the default "ubuntu" user, so it's a good idea to make a new user. I did so.

Oops -- about that Ubuntu new user thing

But at least in Ubuntu Oneiric: there's a problem with that. If you create a user, even as class Administrator (and of course you do want to be an Administrator), it doesn't ask you for a password. If you now log out or reboot, your new user should be saved -- but you won't be able to do anything with the system, because anything that requires sudo will prompt you for your nonexistent password. Even attempting to set a password will prompt you for the nonexistent password.

Apparently you can "unlock" the user at the time you create it, and then maybe it'll let you set a password. I didn't know this beforehand, so here's how to set a password on a locked user from a terminal:

$ sudo passwd username

For some reason, sudo will let you do this without prompting for a password, even though you can't do anything administrative through the GUI.

Testing redux

Once you're logged in as your new user, try making some changes. Add and remove some items from the unity taskbar. Install a couple of packages. Change the background.

Now try rebooting. If your casper-rw file worked, it should remember your changes.

When you're not booted from your live USB stick, you can poke around in the filesystem it uses by mounting it in "loopback" mode. Plug the stick into a running Linux machine, mount it the usb stick, then mount it with

$ sudo mount -o loop /path/to/casper-rw /mnt

/path/to is wherever you mounted your usb stick -- e.g. /media/whatever. With the file mounted in loopback mode, you should be able to adjust settings or add new files without needing to boot the live install -- and they should show up the next time you use the live install.

My live Ubuntu Oneiric install is so much more fun to use now!

Tags: ubuntu, linux, install, grub
[ 15:41 Oct 28, 2011    More linux/install | permalink to this entry | ]

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
/mnt/install.386/vmlinuz

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*
/mnt/install.386/initrd.gz

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!

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

Article: Linux Boot Camp (part 1: SysV Init)

My latest article is up on Linux Planet: How Linux Boots: Linux Boot Camp (Part I: SysV Init)

It describes the boot sequence, from grub to kernel loading to init scripts to starting X. Part I covers the classic "SysV Init" model still used to some extent by every distro; part II will cover Upstart, the version that's gradually working its way into some of the newer Linux releases.

Tags: writing, linux, boot, grub
[ 15:25 Mar 25, 2010    More writing | permalink to this entry | ]

Grub2 Tutorial, Part 3

Part 3 and final of my series on configuring Ubuntu's new grub2 boot menu. I translate a couple of commonly-seen error messages, but most of the article is devoted to multi-boot machines. If you have several different operating systems or Linux distros installed on separate disk partitions, grub2 has some unpleasant surprises, so see my article for some (unfortunately very hacky) workarounds for its limitations.

Why use Grub2? Good question!
(Let me note that I didn't write the title, though I don't disagree with it.)

Tags: writing, linux, boot, grub, ubuntu
[ 10:56 Mar 11, 2010    More writing | permalink to this entry | ]

Grub2 Tutorial, Part 2

Part 2 of my 3-parter on configuring Ubuntu's new grub2 boot menu covers cleaning up all the bogus menu entries (if you have a multiple-boot system) and some tricks on setting color and image backgrounds:

Cleaning up your boot menu (Grub2 part 2).

Tags: writing, linux, boot, grub, ubuntu
[ 22:49 Feb 25, 2010    More writing | permalink to this entry | ]

Grub2 lightning talk at SCALE 8x Ubucon

I gave a lightning talk at the Ubucon -- the Ubuntu miniconf -- at the SCALE 8x, Southern California Linux Expo yesterday. I've been writing about grub2 for Linux Planet but it left me with some, well, opinions that I wanted to share.

A lightning talk is an informal very short talk, anywhere from 2 to 5 minutes. Typically a conference will have a session of lightning talks, where anyone can get up to plug a project, tell a story or flame about an annoyance. Anything goes. I'm a lightning talk junkie -- I love giving them, and I love hearing what everyone else has to say.

I had some simple slides for this particular talk. Generally I've used bold or other set-offs to indicate terms I showed on a slide.

SCALE 8x, by the way, is awesome so far, and I'm looking forward to the next two days.

Grub2 3-minute lightning talk

What's a grub? A soft wriggly worm.

But it's also the Ubuntu Bootloader. And in Karmic, we have a brand new grub: grub2!

Well, sort of. Karmic uses Grub 2 version 1.97 beta4. Aside from the fact that it's a beta -- nuff said about that -- what's this business of grub TWO being version ONE point something? Are you hearing alarm bells go off yet?

But it must be better, right? Like, they say it cleans up partition numbering.

Yay! So that confusing syntax in grub1, where you have to say (hd0,0) that doesn't look like anything else on Linux, and you're always wanting to put the parenthesis in the wrong place -- they finally fixed that?

Well, no. Now it looks like this: (hd0,1)
THEY KEPT THE CONFUSING SYNTAX BUT CHANGED THE NUMBER! Gee, guys, thanks for making things simpler!

But at least grub2 is better at graphics, right? Like what if you want to add a background image under that boring boot screen? A dark image, because the text is white.

Except now Ubuntu changes the text color to black. So you look in the config file to find out why ...

if background_image `make_system_path_relative...
  set color_normal=black/black

... there it is! But why are there two blacks? Of course, there's no documentation. They can't be fg/bg -- black on black wouldn't make any sense, right?

Well, it turns out it DOES mean foreground and background -- but the second "black" doesn't mean black. It's a special grub2 code for "transparent". That's right, they wrote this brand new program from scratch, but they couldn't make a parser that understands "none" or "transparent".

What if you actually want text with a black background? I have no idea. I guess you're out of luck.

Okay, what about dual booting? grub's great at that, right? I have three distros installed on this laptop. There's a shared /boot partition. When I change something, all I have to do is edit a file in /boot/grub. It's great -- so much better than lilo! Anybody remember what a pain lilo was?

#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by /usr/sbin/grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

Oops, wait -- not with grub2. Now I'm not supposed to edit that file. Instead, I edit files in TWO places, /etc/grub.d and /etc/default/grub.conf, and then run a program in a third place, /usr/bin/update-grub. All this has to be done from the same machine where you installed grub2 -- if you're booted into one of your other distros, you're out of luck.

grub2 takes us back to the bad old days of lilo.

FAIL

Grub2 really is a soft slimy worm after all.

But I have some ideas for workarounds. If you care, watch my next few articles on LinuxPlanet.com.

Update: links to Linux Planet articles:
Part 1: Grub2 worms into Ubuntu
Part 2: Cleaning up your boot menu
Part 3: Why use Grub2? Good question!

Tags: grub, ubuntu, linux, boot, speaking, conferences
[ 11:29 Feb 20, 2010    More linux | permalink to this entry | ]

Grub2 Tutorial, Part 1

Upgraded to Ubuntu 9.10 Karmic and wondering how to configure your boot menu or set it up for multiple boots?

Grub2 Worms Into Ubuntu (part 1) is an introductory tutorial -- just enough to get you started. More details will follow in parts 2 and 3.

Tags: writing, linux, boot, grub, ubuntu
[ 17:40 Feb 11, 2010    More writing | permalink to this entry | ]