[Cialug] migrating from ubuntu server to debian

[Matthew Nuzum]

On Thu, Mar 25, 2010 at 6:48 AM, Paul Gray <gray at cs.uni.edu> wrote:
> One other recollection over night -- you may need to generate an /etc/hosts file
> with at least localhost defined.
>

Yep, good catch.

OK, I've now done it successfully in virtualbox twice (I'm loving
snapshots) and these are the steps I used. Once I've completed it on
live I'll blog about it. Actually, I'm also about to upgrade the
software on my blog which is why I'm not blogging about it now.
(waiting till after the change)

Before you start you need to know:

ubuntu-xen-host is the name of my lvm container and in that are root
(volume for ubuntu), swap and I'm creating a new one called debian.

There is a partition for lvm and a separate, non-lvm partition for
/boot at hda5.

The kernel for Debian in this case is 2.6.26-2. It may be different
when you follow these instructions.

This configuration doesn't prevent root from logging into ssh. YOU'LL
WANT TO CHANGE THIS PRONTO. Look in the sshd-config.

It's a good idea to do a little research before and during so that you
know what your UUIDs for your filesystems are. Note that the UUID in
grub's menu.list will point to the /boot filesystem, not to your root
filesystem.

There's really not a lot of risk here until the very end when you're
booted into the new os and you isntall grub. At any point before that
you can reboot and choose the old operating system from the boot menu
and be back to how you once were. Installing grub is technically
optional.

I assume you know how to use vim. You can use a different editor, note
that in the "chroot" section where all the packages are installed
you'd replace vim with your fav.

I strongly urge against doing a copy and paste of these commands for
two reasons:
 1. You should know what you're doing before trying this
 2. My stupid editor had auto-correct on and I didn't realize it and
"corrected" some of the commands. I think I got them fixed but I might
have missed one or two.

Thanks a lot Paul for your tips!

## end of disclaimer, instructions follow

sudo apt-get install debootstrap
sudo lvdisplay
sudo lvcreate -L 8G -n debian ubuntu-xen-host
sudo mkfs -t ext3 -m 1 -v /dev/ubuntu-xen-host/debian
sudo mkdir /mnt/debian
sudo mount -t ext3 /dev/ubuntu-xen-host/debian /mnt/debian/
sudo debootstrap lenny /mnt/debian/ http://debian.cns.uni.edu/debian #
takes a while to download packages
sudo mount --bind /dev /mnt/debian/dev
sudo mount --bind /boot /mnt/debian/boot
sudo chroot /mnt/debian/

## in the chroot now

mount -t proc none /proc
mount -t devpts none /dev/pts
apt-get install ssh locales initramfs-tools vim
linux-image-2.6.26-2-686 lvm2 madam # takes a while to download
packages
# you will get a warning about unsigned packages - enter "Yes"
# you will see many errors about locale and $LANG, ignore for now
# choose "No" to "create a symbolic link to the current kernel image
# choose "No" to "abort initrd kernel image installation?"
# watch the output to make sure that an init ramfs is created - you need this
# it takes a moment so you'll probably see a message, "Generating
/boot/initrd.img…"

dpkg-reconfigure locales

# choose at least en_US.UTF-8 (unless you prefer another language)
# set the default to your chosen language, i.e. en_US.UTF-8

passwd # set the root password
adduser matthew # substitute your user name

## exit chroot

sudo cp /etc/network/interfaces /mnt/debian/etc/network/interfaces
sudo cp /etc/hosts /mnt/debian/etc/hosts
sudo cp /etc/fstab /mnt/debian/etc/fstab
ls /dev/disk/by-uuid/ > /tmp/uuid.list
sudo vim /mnt/debian/etc/fstab /tmp/uuid.list

## in vim change the uuid for the / partition to be the UUID of the
newly created "debian" partition

sudo vim /boot/grub/menu.list
## in vim add the new kernel to the boot menu as the first option
changing the root=… part to match the new filesystem you created
## uuid should remain these same as it should be pointing at your
/boot partition
## also change the kernel path - for example, /vmlinuz-2.6.26-2-686
## and the initrd path to match
## also you may want to comment out the line that says "hiddenmenu"

sudo reboot
## choose the new operating system from the menu

# login as either root or your personal user and su - to root
apt-get install grub
grub-install --no-floppy --recheck /dev/hda

## it's now OK to remove the original partition if you like
## make sure to back up any data
lvremove /dev/ubuntu-xen-host/root


-- 
Matthew Nuzum
newz2000 on freenode, skype, linkedin, identi.ca and twitter