GRUB

Ubuntu 10.04 uses version 1.98 of GRUB (the GRand Unified Bootloader). For more information on bootloaders and the bootstrapping process, start here.

Opening the GRUB menu

Reboot the computer, and either during or just after its POST (where a small blinking cursor like this _ will appear in the upper left hand corner of the screen) press and hold down a Shift key. After a few moments, the text Grub loading... should flash and you'll be presented with a menu with options similar to this:

Ubuntu, with Linux 2.6.32-33-generic
Ubuntu, with Linux 2.6.32-33-generic (recovery mode)
Memory test (memtest86+)
Memory test (memtest86+, serial console 115200)

Here you can move up and down the list of images to boot from, edit their boot parameters, open the GRUB command-line for advanced trickery, and more.

Adding rootdelay

Occasionally a system will fail to boot from a known good, imaged hard drive. Sometimes it's because of defective hardware, and all we can do is replace the parts. But sometimes it's because the bootloader doesn't wait long enough for the drive to respond, and all we need to do is tell the bootloader to wait for just a little longer!

From the GRUB menu:

• Highlight the standard kernel (usually something like Ubuntu, with Linux 2.6.32-33-generic), and press 'e'. You should see something similar to this:

recordfail
insmod part_msdos
insmod ext2
set root='(hd0,msdos1)'
search --no-floppy --fs-uuid --set 732c5f94-8dcb-4622-96ea-797dd2431f90
linux   /boot/vmlinuz-2.6.35-30-generic root=UUID=732c5f94-8dcb-4622-96ea-797dd2431f90 ro   quiet splash
initrd  /boot/initrd.img-2.6.35-30-generic

• Scroll down to the line that starts with linux then scroll to end of the line after splash
• Enter 'rootdelay=60'
• Hit Ctrl+x to boot the image with modified parameters.

The argument for rootdelay is in seconds, though it almost never times out. Most things that would happen with a drive, whether it was working or not, happen relatively quickly.

In order to make this a permanent boot parameter, you can edit the file /etc/default/grub and add rootdelay=60 to the list of arguments assigned to the variable GRUB_CMDLINE_LINUX_DEFAULT.