root=UUID= parameter in GRUB?

kushalkoolwal · 05-16-2008, 12:43 PM

I have been use to "root=/dev/hdX" type of parameter in the GRUB menu. But now a days I see in Ubuntu that they have something like root=UUID=<a-very-large-number>. What does that mean? Where does it come from? Can I replace my "root=/dev/hdX" parameter with "root=UUID=<number>" on other Linux systems like Debian?

Thanks

x_terminat_or_3 · 05-16-2008, 01:33 PM

UUID means Universally Unique Identifier

Basically, it is the label that was assigned to the partition when it was created by the installer.

root=/dev/hdX *MAY* still work, but it is recommended to use labels instead.

kushalkoolwal · 05-16-2008, 02:37 PM

Quote:

Originally Posted by x_terminat_or_3

UUID means Universally Unique Identifier

Basically, it is the label that was assigned to the partition when it was created by the installer.

root=/dev/hdX *MAY* still work, but it is recommended to use labels instead.

Thanks for the info. But how do you actually get it work? How do i find my UUID? and also is UUID going to replace the /dev/hd* in future in Linux in general?

x_terminat_or_3 · 05-16-2008, 02:49 PM

To find the label of the partition,

type in

Code:

e2label /dev/hd*

Replace the * with the appropriate device letter and partition number

No, Linux is still going to use /dev/hd* (or /dev/sd*)

But some distros, like Fedora have switched from using /dev/hd* to using /dev/sd* for all PATA/SATA drives. If your grub references the devices by that name, you wouldn't be able to boot.

You can even mount partitions by their label, example mount LABEL=/home /home would work (provided you have a partition on your system labeled '/home')

warrenc5 · 05-18-2008, 01:52 AM

Hello, I have started using this with the rootwait option, for booting from a usb disk.

Depending on the order the disks are detected by the bios and linux addressing by /dev/sda has no meaning anymore.

The UUID is actually the UUID of the ext2/3 filesystem, which you can see if you use dumpe2fs /dev/sda | grep UUID.

also remember to update your /etc/fstab file.

I have had no success with yaird and root=UUID yaird just seems to translate it to /dev/sdX.