Just spent a while debugging a boot issue caused by blkid treating UUIDs
as case-sensitive:

Gave up waiting for root file system device.  Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT!  PARTUUID=5D75BD2D-6C59-4F73-9762-F4025CA97033 does not exist.  Dropping to a shell!
(initramfs) blkid -l -t PARTUUID=5D75BD2D-6C59-4F73-9762-F4025CA97033 -o device
(initramfs) blkid
/dev/vda1: UUID="83d14a86-02e0-4d48-abda-53b4ed66c8e0" TYPE="ext4" PARTUUID="5d75bd2d-6c59-4f73-9762-f4025ca97033"
(initramfs) blkid -l -t PARTUUID=5d75bd2d-6c59-4f73-9762-f4025ca97033 -o device
/dev/vda1

I would normally expect a string of hexadecimal to not care about the
case of the a-f digits. Either this needs documenting somewhere, or it
needs fixing in blkid.

Hello Josh Triplett,

Thanks for your bug report.

Please feel free to report this as an issue to upstream[1]. However you
might also want to note that blkid is in deep maintenance mode as it
has been superseeded by the more easily extendable lsblk utility.
Maybe it would thus be better to consider reporting this as a wishlist
bug against initramfs-tools (and consider its current usage of blkid
as an implementation detail that possibly could be changed to fix this).

Regards,
Andreas Henriksson

[1]: https://github.com/karelzak/util-linux/issues or mailinglist on
     vger.kernel.org

I don't think I'd consider this bug to be an initramfs-tools bug, but if
blkid is considered somewhat deprecated in favor of lsblk, it certainly
seems reasonable for initramfs-tools to consider switching.

- Josh Triplett