Arch Linux

Gendalf@Arch

Member

Registered: 2022-09-18

Posts: 9

[SOLVED] LUKS on LVM, separate /usr partition

Hi all, I was trying to install Arch with LUKS on LVM, with a separate /usr partition and it didn't work. During the boot after prompt/decryption and mounting of /dev/mapper/root I was getting the following:

::running late hook [usr]
ERROR: device '' not found. Skipping fsck.
:: mounting '' on /usr
mount ... failed: Can't lookup blockdev.

I can't share more details as I went ahead with installation without separate /usr. Though I am curious about possible reasons why the above didn't work (theoretically) and if someone else has LUKS on LVM with separate /usr working.

My guess is that 'usr' hook is invoked before cryptsetup logic for /etc/crypttab (where decryption of the 'usr' LVM volume is configured) and therefore the block device to mount wasn't ready. Though I may be wrong and keen to find out the reason

HOOKS=(base udev autodetect microcode keyboard keymap modconf block encrypt lvm2 usr filesystems resume fsck)

Last edited by Gendalf@Arch (2025-04-22 11:50:00)

frostschutz

Member

Registered: 2013-11-15

Posts: 1,544

Re: [SOLVED] LUKS on LVM, separate /usr partition

usr is a late hook so it should run after rootfs was already mounted.

Did you not have an fstab entry for it? (Or not updated initcpio after editing fstab)

Anyhow, separate /usr rarely makes sense these days. It's better to not separate it.

Gendalf@Arch

Member

Registered: 2022-09-18

Posts: 9

Re: [SOLVED] LUKS on LVM, separate /usr partition

Thanks for the info!
I had all the entries in fstab, generated by genfstab. Must have mistyped something somewhere else. It is good to know though about the hook being late and that it should work by design combined with LUKS on LVM.
Yeah, also after some search can see separate /usr is not that important. I was exploring an option to set nodev on /usr.