Ubuntu – How to properly update Grub in Hosted environment

bootgrub2installation

I'm hoping to obtain some guidance to properly update Grub on a GoDaddy dedicated server, as my previous attempt has resulted in re-provisioning the server. If this were a local server, I think I could start the server from the console and make the necessary configuration changes. Being hosted, I don't have access to the console – or so I believe, so I'm stuck with a server I can no longer access.

To start, I'm using apt-get upgrade (as I'm ultimately trying to upgrade from Lucid to Precise). This then identifies the Grub update..

There are two separate prompts which I'm unsure how to properly proceed:

1) Grub configuration
The update asks what I want to do with the config file (/etc/default/grub?).
Should I

Keep my existing
Replace with package
Merge existing with package
Other

2) Installation location
A second prompt is to install the boot loader. The guide suggests that if I don't know, I should install it to all locations.
/boot is located on /dev/sda1
/dev/sda3 contains everything else (eg /)

Is /boot the only place it needs to be located, or do I need to identify something in /boot/grub/grub.cfg to identify where it should be installed?

Best Answer

1. Grub configuration:

First of all, make a backup of /etc/default/grub file. This file is used to generate /boot/grub/grub.cfg with update-grub command. Feel free to keep existing, but i'd reccomend you to merge with package and compare merged with a backup copy. Do not replace with package. The system can be unbootable. /boot/grub/grub.cfg file will be regenerated at the end of update process. So, inspect the final version of /etc/default/grub, modify it if needed, run update-grub command if modified.

2. Installation location:

/boot is the only one location GRUB2 places it's files, but it also embed some code into MBR/boot partition. So, if /boot located on a separate partition and this partition is marked as bootable - choose /boot. If another partition is marked as bootable (/ for example - choose all locations).

On UEFI systems GRUB2 places additional files on /boot/efi.

Related Solutions

Ubuntu – Server boots to grub prompt after reboot

I've figured this one out now.

The solution here did it for me: https://serverfault.com/questions/243343/headless-ubuntu-server-machine-sometimes-stuck-at-grub-menu

I changed my /etc/grub.d/00_header and edited the recordfail section to:

if [ \${recordfail} = 1 ]; then
  set timeout=${GRUB_TIMEOUT}
else
  set timeout=${GRUB_TIMEOUT}
fi
EOF

Ran sudo update-grub, rebooted and it booted straight into Ubuntu. Yipee!

Ubuntu – grub2: update-grub failed to get canonical path of `none’

Ok I seem to have got it with the following (everything is simple in retrospect):

$ umount /boot

I tried this as I noticed that there were two 'mounts' for /boot:

$ mount -l |grep boot
/dev/md1 on /boot type ext3 (rw,relatime,data=ordered)
none on /boot type aufs (rw,relatime,si=6ea5aad590be877d)

And that the latter was overriding the former:

$ df -h |grep boot
none            436G  178G  236G  44% /boot

After umount the same commands look like this:

$ mount -l |grep boot
/dev/md1 on /boot type ext3 (rw,relatime,data=ordered)
$ df -h |grep boot
/dev/md1        488M   75M  388M  17% /boot

(no idea how the second mount happened)

I was then able to reinstall grub as follows (I've raid1 so that's why there's two commands for sda and sdb):

$ grub-install /dev/sda
Installing for i386-pc platform.
Installation finished. No error reported.
$ grub-install /dev/sdb
Installing for i386-pc platform.
Installation finished. No error reported.
$ update-grub
Generating grub configuration file ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-3.19.0-30-generic
Found initrd image: /boot/initrd.img-3.19.0-30-generic
Found linux image: /boot/vmlinuz-3.19.0-25-generic
Found initrd image: /boot/initrd.img-3.19.0-25-generic
done

Postscript

After reboot the server came back up (could ping it), but I found I couldn't ssh in. This turned out to be a separate problem to do with /dev/null (might have gotten broken at the same time). I was able to ssh in using a separate rescue system and apply this fix: http://thesystemadministrator.net/linux-administration/sshd-deamon-failing-to-start