If a fsck takes longer than 90 seconds during boot, the systemd unit times out and the system falls into emergency mode. This is obviously very unfortunate with headless devices without KVM, as the issue cannot not be fixed or atleast diagnosed from the outside.
The exact lines given are:
[ TIME ] Timed out waiting for device dev-disk-by-partuuid-xxx
[DEPEND] Dependency failed for /boot
[DEPEND] Dependency failed for Local File Systems.
[DEPEND] Dependency failed for File System Check on /dev/disk/bypartuuid/xxx
The offending partition is the boot-partition (FAT-filesystem) on a raspberry pi. Even though the partition is only 41MB big, the fs-check takes longer than 90 seconds. I've never had this issue with ext2/3/4-partitions.
How can I fix this issue?