not all disks created in /dev/disks/by-uuid

[ooops]

Binary package hint: udev

I am not sure that the problem is with udev. But anyhow, I have an inconsistency with /dev/disks/by-uuid. The filesystem /dev/sda5 is not in /dev/disks/by-uuid. But I can mount it specifying the device. And it was there after installation (note that I have replaced the UUID mount in /etc/fstab with the device-mount to be able to boot). There was a dbus- and a kernel-update. But none of those look very suspicious.

Any idea how to debug this? What kind of log do you need?

$ sudo tune2fs -l /dev/sda5 |grep UUID
Filesystem UUID: f9b5a20e-4270-45f9-ab2a-09196a50a80c
$ ls -l /dev/disk/by-uuid/
total 0
lrwxrwxrwx 1 root root 10 2009-10-04 20:37 8378e311-ccbb-4956-9732-a7f47ec81b74 -> ../../sda3
lrwxrwxrwx 1 root root 10 2009-10-04 20:37 94340636-b074-49f0-ab04-1d6dac575a9d -> ../../sda1
lrwxrwxrwx 1 root root 10 2009-10-04 20:37 a3b47868-5540-4994-a363-b8b0ffaa1ab3 -> ../../sda6
lrwxrwxrwx 1 root root 10 2009-10-04 20:37 daf72b11-bd81-4e65-9c40-064b17333523 -> ../../sda2
$ grep f9 /etc/fstab
#UUID=f9b5a20e-4270-45f9-ab2a-09196a50a80c /home ext3 defaults 0 2
$ grep sda5 /etc/fstab
# /home was on /dev/sda5 during installation
/dev/sda5 /home ext3 defaults 0 2
# /dev/sda5
$ mount |grep sda5
/dev/sda5 on /home type ext3 (rw)

[Gabriel de Perthuis (g2p)]

I tracked down an unbootable karmic upgrade to this.

Why not having by-uuid symlinks makes the system unbootable:

mountall blocks (can't find the /boot partition in by-uuid), and upstart doesn't start the system.

Why udev doesn't create the by-uuid symlinks:

udev relies on libblkid1 from util-linux to create them.
sudo blkid -p $DEVICE
says the device has ambiguous uuid.
sudo BLKID_DEBUG=0xffff blkid -p $DEVICE
says there's a vfat uuid in there as well, in the first 512 bytes that ext2/ext3 ignores.

How to make sure by-uuid symlinks still work in karmic:

Having mke2fs zero the first 512 bytes of a partition would solve the problem, but for new installs only.
IMHO, the consequences are important enough that this should be disambiguated using the partition table.

(To start the system anyway, try the not so simple hacks at http://upstart.ubuntu.com/wiki/OMGBroken and edit /etc/fstab to use /dev/sdXN notation for the uuids that don't work.)