booting from uuid with grub

alex.blackbit · Advocate Joined: 26 Jul 2005 Posts: 2397

hi,

i am confused.
since i have some problems with persistent storage names, i wanted to move to using UUIDs.
they work as expected in /etc/fstab.
but i can't get them to work in grub.
what do i have to do to use them ?
there are several web references that tell a syntax like

Gentree · Posted: Mon Nov 09, 2009 3:44 pm Post subject:

IMHO UUIDs suck . Basically for being totally unreadable to humans.

yesterday I had a mate with a system that had had several mandrake/suse installations and needed fixig. I needed to see what's what. I mounted the partition , looked at /etc/fstab and got a face full of UUID. Cool!

Also you lose the uuid if you reformat or resize a partition.

The current mode for handling virtually all periferals as /dev/sd* is the root of much of this. There may be ways around that situation depending upon hardware. Firstly use libata for ATA drives. This is NOT deprecated, use it.

If you're really intent on uuids I think you need to experiment with grub-2, make you own choice if that is "stable" enough to be used. I doubt it.

I suspect trying to making device names less volatile would be the better route.

_________________
Linux, because I'd rather own a free OS than steal one that's not worth paying for.
Gentoo because I'm a masochist
AthlonXP-M on A7N8X. Portage ~x86

alex.blackbit · Advocate Joined: 26 Jul 2005 Posts: 2397

thanks for your thoughts.
any info on booting from disk labels with grub 0.9? ?

sidarali · n00b Joined: 13 Nov 2007 Posts: 3

You need initird to use UUIDs.

In grub.conf when you specify root partition using uuid - kernel doesn't know what does that mean.

2 Gentree: I use UUIDs because on our fileserver hard drives connected to sata controllers appear before drives connected to motherboard sata ports - system drive sda becomes sdb while drive connected to additional SATA controller drive becomes sda. So each time we add hard drive to the system configs need to be updated.

Gentree · Posted: Fri Apr 02, 2010 9:04 pm Post subject:

IMHO the best way to avoid that kind of insanity is to stop pretending everything connected to the machine is a scsi device. Use pata driver for pata drives not scsi-sata simulation.

hda is always hda

_________________
Linux, because I'd rather own a free OS than steal one that's not worth paying for.
Gentoo because I'm a masochist
AthlonXP-M on A7N8X. Portage ~x86

i92guboj · Posted: Mon Apr 19, 2010 10:28 am Post subject:

Gentoo, not really.

hda will be hda as long as your kernel says it's hda. Just add another drive, change disk order, reconfigure your kernel in a different way or reorder some options in your BIOS and you will be stuck at the same silly problem each time. Thanks dog grub let you edit your boot options in real time, but that's not quite an optimal solution.

The real solution is to use an unique ID for a given device, that's absolutely the only way to make really sure that you are using the correct device, unless your box is completely closed to both hardware and software updates.

There's absolutely no downside to using UUIDs, and your argument about them being unreadable is rather poinless, considering that "hda1" is not any more human readable. It doesn't tell you which disk are you using at all, the details will depend on the many factors I told you above. Unless you do a very careful study about the BIOS and the physical connections there's no way to tell what "hda" means. On the contrary, an unique ID will always belong to one (and only one) concrete device. People who continuously need to change their hardware configuration know what they talk about when they want and pray for UUID support in grub and fstab.

Gentree · Posted: Mon Apr 19, 2010 4:25 pm Post subject:

i92guboj · Posted: Mon Apr 19, 2010 4:35 pm Post subject:

pigeon768 · l33t Joined: 02 Jan 2006 Posts: 683

SilverChild · n00b Joined: 25 Apr 2010 Posts: 1

FYI: UUID are tied to a partition not hard drive.
they also help when you have Linux installed on a USB powered hard drive and you never know when your drive will show up as sd[a|b|c|d|e|...]3. Using a UUID will always guarantee that you will mount the correct partition on the correct drive as your root and correctly mount any other mount points as well. That being said. If you don't want to use UUIDs then don't. I use them when I need them. The nice thing about Linux is what every way works for you is the right way!

cyrillic · Posted: Sun Apr 25, 2010 12:49 am Post subject: Re: booting from uuid with grub

_Flame_ · n00b Joined: 14 Feb 2010 Posts: 47

Try - "real_root=uuid"

Element Dave · Tux's lil' helper Joined: 10 Nov 2006 Posts: 82

andrewwalker27 · l33t Joined: 27 Jun 2005 Posts: 660

I think the idea of uuid's is good but, as I'm finding out to my cost, getting it working is as problematic as /dev/sd*. The reason I tried to use uuid was because my usb internal card reader screws up my /dev/sd* chain. Sadly decent up-to-date documentation of howto guides are hard to come by and setting up an initrd image is a nightmare if you don't really even understand why it's necessary.
What's really needed is a proper wiki page on how to set up Gentoo to boot grub using uuid's as that seems the way the rest of the Linux world seems to be going.

darkphader · Veteran Joined: 09 May 2002 Posts: 1217 Location: Motown

s4e8 · Guru Joined: 29 Jul 2006 Posts: 311

kernel >= 2.6.37, recognize the partition uuid, not filesystem uuid. older kernel don't support anything root by uuid.
partition uuid supported by EFI GPT, the correct grub commandline is
root=PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF