Help with fstab/uuid

[reidr]

Hi. I recently used preupgrade to go from Fedora 9 to the prerelease of 10. It all went pretty smoothly, including, I'm pretty sure, a few reboots afterwards. A few days after upgrading, I yum upgraded a bunch of packages. A subsequent reboot caused a mess. It wasn't able to find my / partition because something modified fstab to refer to UUIDs instead of /dev locations. I was dumped to a shell prompt to fix it. Fortunately, I had an old Fedora 7 rescue CD laying around, and that was enough to let me fix the fstab file. Here's what's in it now:

#UUID=49b3d627-d156-4b79-a18b-2cb3f2fdaf86 / ext3 defaults 1 1
/dev/mapper/VolGroup00-LogVol00 / ext3 defaults 1 1

(Not the whole file, of course.) The first line is what it had put in; the second is what it used to read, and what I changed it back to. (I'm using LVM.)

I also had a similar problem with an external USB hard drive that is always connected (for backups) and is also in fstab:

#UUID=a95dbd67-35ee-4332-af7d-89869d5cc2f0 /mnt/disk2 ext3 defaults 1 2
#LABEL=/mnt/disk2 /mnt/disk2 ext3 defaults 1 2

In this case, the UUID line failed, but so did the LABEL line (which had always worked). I had to comment out both before I could login. (Aside: shouldn't drives like that be non-fatal? It was annoying to have to go back to the rescue disk so often.) I don't know why it failed. After logging in, I was able to manually mount it using the label. That's where I stand right now.

I understand UUIDs are like LABELs. I'm guessing the first problem was caused because the UUID for the / partition may not be known. Here's my entire /dev/disk/by-uuid:

lrwxrwxrwx 1 root root 10 2008-11-19 23:15 5d4eb3c8-3224-42ff-933c-00dc7d858f57 -> ./../sda1
lrwxrwxrwx 1 root root 10 2008-11-19 23:15 660d1314-5009-4120-a630-c4cab2491344 -> ./../sdb1
lrwxrwxrwx 1 root root 10 2008-11-19 23:15 a95dbd67-35ee-4332-af7d-89869d5cc2f0 -> ./../sdg1

And fdisk -l:

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000b1769

Device Boot Start End Blocks Id System
/dev/sda1 * 1 25 200781 83 Linux
/dev/sda2 26 60801 488183220 8e Linux LVM

Disk /dev/sdb: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x41ffc810

Device Boot Start End Blocks Id System
/dev/sdb1 1 38913 312568641 83 Linux

Disk /dev/sdg: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x56fa7c5b

Device Boot Start End Blocks Id System
/dev/sdg1 1 60801 488384001 83 Linux

(There's a second external firewire drive, sdb1, that worked okay.)

blkid shows this for my / partition:

/dev/mapper/VolGroup00-LogVol00: UUID="49b3d627-d156-4b79-a18b-2cb3f2fdaf86" TYPE="ext3" SEC_TYPE="ext2"

I'm pretty lost in all this, but it seems like it has a UUID, but it may never be seen. Now that it's not referring to the UUID in fstab, I guess it should be okay, but it still makes me nervous. I have no idea what's wrong with my external drive. Maybe that will be fixed on a reboot, but I'm dreading more rounds of rescue cd/fix fstab/reboot. Does anyone know what's going on?

Apologies if I left out anything useful, will post more as necessary! Here's my kernel rpm:

kernel-2.6.27.5-117.fc10.x86_64

Thanks,
reid

[stoat]

Hello reidr,

Well, it sounds like you have it booting and working again by using the device mapper device name for the root logical volume in the fstab again. And the remaining issue is the external drive. Right? I wondered what (if anything) you noticed while it was commented out in the fstab. My experience with externals not listed in the fstab is for the desktop environment (Gnome and XFCE both did this) to mount the partitions under /media and even put icons for them on the desktop. If that happened in your case, it might be just as acceptable because the partition label makes the moint point consistent every time even if the device name is different.

[reidr]

Hi stoat, thanks for the reply. I think I am okay with my root partition now that I've changed my fstab, but I am curious a) what changed it; b) will it change again; and c) should I be concerned that my root partition isn't showing up under /dev/disk/by-uuid. And am I no longer doing things the Right Way.

The external drive is used to backup the main drive every night in a cron job (using BackupPC). I never really remove it, which is why I added it to fstab. I ran into problems trying to get it to mount on demand with autofs (can't even remember the details there), and I'd like it to work all the time, even when no one is logged in. I'm also a little disturbed about it not working in fstab with either UUID or LABEL.

So in general, I'm back in decent shape, but a bit wary.

Thanks,
reid

[stoat]

Originally Posted by reidr

And am I no longer doing things the Right Way.

First, I don't think what you did is so wrong. Fedora 9 uses UUID, and I changed that back to labels in the fstab and grub.conf. No problems. Second, I also don't think it will change again as you are asking. It was the upgrade that changed all of that, and that's done and over with.

I don't really know what else to say about the external drive. That was my very best idea. BTW, the effect that I reported with Gnome and XFCE occurred without autofs even being installed.

[reidr]

Sounds good. I appreciate your reassurance. I'll try fiddling around a bit with the external drive one of these days to see if it's gotten better or if I should try autofs or something again. I just unloaded some images from a digital camera in gnome, and it was a piece of cake, so I appreciate how they handle things like that!