On my disks, I make several relatively small partitions, maybe 15G or so (pause to laugh about what I would have thought ten or even five years ago if someone told me I'd be referring to 15G as "small"), one small shared /boot partition, a swap partition, and use the rest of the disk for /home or other shared data.
Now you can install a new release, like 9.04, onto a new partition without risking your existing install.
If you prefer upgrading rather than running the installer, you can do that too. I needed a jaunty (9.04) install to test whether a bug was fixed. But my intrepid (8.10) is working fine and I know there are some issues with jaunty, so I didn't want to risk the working install. So from Intrepid, I copied the whole root partition over to one of my spare root partitions, sda5:
mkfs.ext3 /dev/sda5 mkdir /jaunty mount /dev/sda5 /jaunty cp -ax / /jaunty(that last step takes quite a while: you're copying the whole system.)
Now there are a couple of things you have to do to make that /jaunty partition work as a bootable install:
1. /dev on an ubuntu system isn't a real file system, but something magically created by the kernel and udev. But to boot, you need some basic stuff there. When you're up and running, that's stored in /dev/.static, so you can copy it like this: cp -ax /dev/.static/dev/ /jaunty/
2021: Ignore this whole section. For several years, Linux distros have been able to create /dev on their own, without needing any seed files. So there's no need to create any devices. Skip to #2, fstab which is definitely still needed.
Note: it used to work to copy it to /jaunty/dev/. The exact semantics of copying directories in cp and rsync, and where you need slashes, seem to vary with every release. The important thing is that you want /jaunty/dev to end up containing a lot of devices, not a directory called dev or a directory called .static. So fiddle with it after the cp -ax if you need to.
Note 2: Doesn't it just figure? A couple of days
after I posted this, I found out that the latest udev has removed
/dev/.static so this doesn't work at all any more. What you can do
Note 3: If you're running MAKEDEV from Fedora, it
will target /dev instead of the current directory, so you need
MAKEDEV -d /whatever/dev generic
. However, caution: on Debian and Ubuntu -d deletes the devices. Check
man MAKEDEV first to be sure.
Ain't consistency wonderful?
2. /etc/fstab on the system you just created points to the wrong root partition, so you have to fix that. As root, edit /etc/fstab in your favorite editor (e.g. sudo vim /etc/fstab or whatever) and find the line for the root filesystem -- the one where the second entry on the line is /. It'll look something like this:
# /dev/sda1 UUID=f7djaac8-fd44-672b-3432-5afd759bc561 / ext3 relatime,errors=remount-ro 0 1
The easy fix is to change that to point to your new disk partition:
# jaunty is now on /dev/sda5 /dev/sda5 / ext3 relatime,errors=remount-ro 0 1
If you want to do it the "right", ubuntu-approved way, with UUIDs, you can get the UUID of your disk this way:
ls -l /dev/disk/by-uuid/ | grep sda5
Take the UUID (that's the big long hex number with the dashes) and put it after the UUID= in the original fstab line.
While you're editing /etc/fstab, be sure to look for any lines that might mount /dev/sda5 as something other than root and delete them or comment them out.
The following section describes how to update grub1. Since most distros now use grub2, it is out of date. With any luck, you can run update-grub and it will notice your new partition; but you might want to fiddle with entries in /etc/grub.d to label it more clearly.
Now you should have a partition that you can boot into and upgrade. Now you just need to tell grub about it. As root, edit /boot/grub/menu.lst and find the line that's booting your current kernel. If you haven't changed the file yourself, that's probably right after a line that says:
## ## End Default Options ##It will look something like this:
title Ubuntu 8.10, kernel 2.6.27-11-generic uuid f7djaac8-fd44-672b-3432-5afd759bc561 kernel /vmlinuz-2.6.27-11-generic root=UUID=f7djaac8-fd44-672b-3432-5afd759bc561 ro initrd /initrd.img-2.6.27-11-generic
Make a copy of this whole stanza, so you have two identical copies, and edit one of them. (If you edit the first of them, the new OS it will be the default when you boot; if you're not that confident, edit the second copy.) Change the two UUIDs to point to your new disk partition (the same UUID you just put into /etc/fstab) and change the Title to say 9.04 or Jaunty or My Copy or whatever you want the title to be (this is the title that shows up in the grub menu when you first boot the machine).
Now you should be able to boot into your new partition.
Most things should basically work -- certainly enough to start
do-release-upgrade without risking your original
[ 10:44 May 13, 2009 More linux/install | permalink to this entry | ]