Bug#852323: Problem: UUIDs not being used everywhere for disks in stretch

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

Hello all,

On Fri, 19 Apr 2019 13:17:32 +0100 Steve McIntyre <steve@einval.com> wrote:
> *In the installer*, we're not seeing *any* "change" events for the
> hard disk (vda in my case), in either stretch or buster. We just get
> the "add" and "remove" events. In the buster installer, my temporary
> hack of forcing the "udevadm trigger" means that the UUIDs are updated
> for Grub to use, but it's clearly not a correct final solution.
>
> Yet... in both cases in the post-installer runtime we're getting the
> "change" events when I do the mkfs.
>
> Is udev maybe built differently for the installer

Looks like a good guess.

Udev has a rule with OPTIONS+="watch" to trigger a change event and 
update symlinks in /dev/disk/by-{uuid,label} when writing to a block 
device. In Jessie, the "watch" rule was located in the file
/lib/udev/rules.d/60-persistent-storage.rules.
In Stretch and Buster, the "watch" rule was moved to a new file
/lib/udev/rules.d/60-block.rules.
However this new file was not included in :

- the initramfs hook script /usr/share/initramfs-tools/hooks/udev, 
therefore in the initramfs built by update-initramfs

- the udev-udeb package

- the Debian installer initrd.gz (I guess it uses udev-udeb)

For those still interested I submitted bug #958397 against udev-udeb.
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=958397>