How to resize the root partition of a remote server

You have a (Debian) Linux server at some web hoster and you want to change the partition table. Unfortunately, there is just one big partition on which your linux resides.

But there is a way to do it if you have a swap partition that's big enough: Create a small Linux on your swap partion. Boot it and resize/repartition your current root partition. Finally, you can reboot your old Linux on the reduced partition. Here is a step-by-step manual showing how to do it.

Dectivate swap:

$ swapoff -a

Change the partition type of the swap partition to linux (83) using (c)fdisk.

Format the partition (hdaX stands for your swap partition):

$ mkreiserfs /dev/hdaX

Copy the whole file system there:

$ mount -o notail /dev/hdaX /mnt

$ tar clf - -C / .| tar xf - -C /mnt

Change the /mnt/etc/fstab:

• root must be /dev/hdaX and of type reiserfs with option notail
• swap must be commented out.

If the swap partition is too small for your current file system, you can debootstrap a new one there. But check the networking configuration afterwards - otherwise you won't reach your machine.

Change /etc/lilo.conf:

• Duplicate the currently active entry
• Change the image path of the copy to /mnt/boot/vmlinuz-....
• Change/add "root=/dev/hdaX"
• But leave the current one the default!

Run lilo to check if /etc/lilo.conf is correct:

$ lilo

If you want, you can reboot now to make sure you didn't make any mistake so far.

Run

$ lilo -R LinuxSwap

reboot

$ shutdown -r now; exit

wait until your machine is up again, log on and check with

$ df

whether you booted from the swap space.

Now make the swap partition the default:

Reboot back to your old partition:

$ shutdown -r now; exit

When the machine is up again change /etc/lilo.conf so that LinuxSwap is the default.

Run lilo again:

$ mount /dev/hdaX /mnt

$ lilo

Reboot:

$ shutdown -r now; exit

From now on, your machine will always boot from the former swap partition.

Delete your old root partition and create a new one with parted, fdisk or cfdisk.

$ mkreiserfs /dev/hdaY

$ mount -o notail /dev/hdaY /mnt

$ tar clf - -C / .| tar xf - -C /mnt

Change the /mnt/etc/fstab so that root is /dev/hdaY

Finally, I made lilo boot the old partition again, rebooted and turned the former swap partition back into a swap partition.

I recommand running lilo from the new root disk.

Check that in /mnt/etc/lilo.conf, the default points to the new root disk.

Change the root device back to /dev/hdaY in /mnt/etc/fstab.

Run lilo in chroot:

$ mount /dev/hdaX /mnt/mnt/

$ chroot /mnt/

$ lilo

(You can ignore the warnings)

Now you can reboot:

$ exit

$ shutdown -r now;exit

Once you are logged in again, check again where you are:

$ df

Turn /dev/hdaX back to swap partition

$ mkswap /dev/hdaX

Change the partition type of /dev/hdaX back to Linux Swap (82) with parted, fdisk or cfdisk

Edit /etc/fstab and remove the comment from swap

Reboot one more time and check whether you have again swap:

$ df

Now you are done!

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