Rescuing your dedicated server

This page will help you fix your Bytemark dedicated host in the event that it won’t boot, showing you how to use the network boot system to fix your server via the “dedicated host shell

I’ll assume you’ve booted into the appropriate netboot-rescue and are wondering what to do next.

Mount your drives

This could be a bit more automatic (so when we release the second netboot-rescue, these instructions will go away) but isn’t very hard to get right.

Your filesystem will be on a device called:

• /dev/hda (single-disc servers before mid-2005)
• /dev/md0 (any two-drive servers running software RAID)
• /dev/sda (single-disc servers after mid-2005 or hardware RAID devices)

and the kernel boot messages will display what’s detected during boot.

Hardware RAID?

If you have paid extra for hardware RAID, one of these commands will insert the appropriate disc driver:

modprobe 3w-xxxx
modprobe 3w-9xxx

Whichever one works will print out some console messages about /dev/sda which is your root device.

Software RAID?

If you have a normal software RAID system you will need to bring up the RAID manually:

mdadm -A /dev/md0 /dev/sda1 /dev/sdb1

e.g. will create device /dev/md0 based on the contents of /dev/sda1 and /dev/sdb1 . If you are not sure what partitions you have on your drives you can run:

sfdisk -d /dev/sda
sfdisk -d /dev/sdb

which will print out your drives’ partition tables.

If Bytemark set up your system, you should just need to repeat the mdadm command for as many partitions as you have, more recently we only set up a single partition.

Don’t worry, mdadm won’t “force” together partitions which weren’t part of the same array.

Mount your filesystem

When you know where your root filesystem is (it will be one of /dev/sda1 or _/dev/md0)

mount /dev/sda1 /target 

What next?

For simple problems, you should just be able to edit files in /target (which represents your normal filesystem) without any problems.

If you need to re-run LILO, grub or any binaries from within the “real” system you can do:

chroot /target

in order to enter your system’s normal environment. You may also need to run:

mount /proc
mount /sys

to make many commands work properly.

Finished?

Just press ctrl+D a few times and the system will reboot