Arch Linux

d_adler

Member

Registered: 2026-05-02

Posts: 3

[SOLVED] Tmed out waiting for device /dev/mapper/root

hi

The timout first occurred after an upgrade on reboot into the new kernel.

My attempts to fix so far, using an arch installation medium:

fsck on all filesystems.

Used cryptsetup and mount to get filesystem ready for arch-chroot into sys.

re-installed some packages (everything in base, mkinitcpio,  grub, efibootmgr, kernel and some more)

With the line

HOOKS=(base systemd autodetect microcode modconf kms keyboard sd-vconsole block sd-encrypt filesystems fsck)

in /etc/mkinitcpio.conf I re-generated the initramfs with

# mkinitcpio -P

ran

# grub-install --target=x86_64-efi --efi-directory=/boot --bootloader-id=GRUB

and edited /etc/defaults/grub to

GRUB_CMDLINE_LINUX_DEFAULT="cryptdevice=/dev/nvme0n1p3:root loglevel=3 quiet"

ran

# grub-mkconfig -o /boot/grub/grub.cfg

The resulting line in grub.cfg is

linux    /vmlinuz-linux root=UUID=62de5c67-e5b0-4da3-94a1-ebd8514d2d99 rw  cryptdevice=/dev/nvme0n1p3:root loglevel=3 quiet

# blkid
/dev/nvme0n1p3: UUID="6ee72456-089d-4a52-90ed-3c46d5c25200" TYPE="crypto_LUKS" PARTUUID="4f1616f3-d95a-4158-b0bf-a72cd2f9d965"
/dev/nvme0n1p1: UUID="8A86-3885" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="41006022-7a8e-473b-aeef-78fedc7c9eff"
/dev/nvme0n1p4: UUID="54cdd234-b0bb-419e-830d-a76d1a537aa0" TYPE="crypto_LUKS" PARTUUID="4121aad4-1597-491a-95dc-d64571385579"
/dev/nvme0n1p2: UUID="62a500ab-fd5c-4f99-b331-fbd3a9803981" TYPE="swap" PARTUUID="6863f29f-50d9-4a67-ab5d-06db3127938a"
/dev/mapper/home: UUID="9ef76bbb-35c3-493f-a374-375131b8e675" BLOCK_SIZE="4096" TYPE="ext4"
/dev/loop0: BLOCK_SIZE="1048576" TYPE="squashfs"
/dev/mapper/root: UUID="62de5c67-e5b0-4da3-94a1-ebd8514d2d99" BLOCK_SIZE="4096" TYPE="ext4"
/dev/sda2: LABEL_FATBOOT="ARCHISO_EFI" LABEL="ARCHISO_EFI" UUID="69F4-4294" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="a7240684-02"
/dev/sda1: BLOCK_SIZE="2048" UUID="2026-05-01-06-05-08-00" LABEL="ARCH_202605" TYPE="iso9660" PARTUUID="a7240684-01"

# lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
loop0         7:0    0 973.1M  1 loop 
sda           8:0    1   7.5G  0 disk 
├─sda1        8:1    1   1.2G  0 part 
└─sda2        8:2    1   253M  0 part 
nvme0n1     259:0    0 238.5G  0 disk 
├─nvme0n1p1 259:1    0     1G  0 part  /boot
├─nvme0n1p2 259:2    0     5G  0 part 
├─nvme0n1p3 259:3    0    40G  0 part 
│ └─root    253:0    0    40G  0 crypt /
└─nvme0n1p4 259:4    0 192.5G  0 part 
  └─home    253:1    0 192.5G  0 crypt /home

After all this didn't help. I reformatted partitions except /home and newly installed around the /home partition but the error remains the same.

I now need help, being at my wits' end.  10a+ Arch user so not really a newbie but I very much feel like one today thus posting it here.

cheers
     David

Last edited by d_adler (2026-05-02 19:14:48)

Scimmia

Fellow

Registered: 2012-09-01

Posts: 13,726

Re: [SOLVED] Tmed out waiting for device /dev/mapper/root

cryptdevice is the option for the encrypt hook, not for the sd-encrypt hook.

d_adler

Member

Registered: 2026-05-02

Posts: 3

Re: [SOLVED] Tmed out waiting for device /dev/mapper/root

Thanks Scimmia, I'm now reading through https://wiki.archlinux.org/title/Dm-cry … -generator which is -- as I now understand -- what applies to sd-encrypt.

d_adler

Member

Registered: 2026-05-02

Posts: 3

Re: [SOLVED] Tmed out waiting for device /dev/mapper/root

Solution:
In /etc/defaults/grub, replaced
cryptdevice=/dev/nvme0n1p3:root
with
rd.luks.name=<UUID>=root rd.luks.name=<UUID>=home
re-ran grub-mkconfig and it worked.

Note to self (and others):
never try and read documentation on a narrow phone screen, you'll loose track of sectioning.

I can't figure out how this occurred in the first place, since it had worked for ages and I hadn't made any changes prior to the faulty reboot.
Seems I had used the encrypt hook before, not sd-encrypt, as there's a now obsolete /etc/crypttab file once used to unlock the home dir.

Thanks!

keitolainen

Member

Registered: 2015-06-08

Posts: 10

Re: [SOLVED] Tmed out waiting for device /dev/mapper/root

Thank you, this was very helpful. I had the same issue, however I use the "encrypt" hook in /etc/mkinitcpio.conf, and not the "sd-encrypt" hook. It was working fine until a kernel upgrade the other day, same as you. It turns out I had been using:

HOOKS=(base systemd autodetect microcode modconf kms keyboard keymap sd-vconsole block encrypt lvm2 filesystems fsck)

Changing it to the following solved the problem:

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

The default hooks had changed to use systemd at some point, and I did not realize that would conflict with the "encrypt" hook, so I simply added it and "lvm2," as I normally did. This worked fine for months, until I updated the kernel this week. Then the system no longer booted, same as you.

My guess is the update removed a fallback option to use the appropriate hooks based on which encryption hook is specified, so suddenly incorrect config files caused a failure.