[systemd-devel] Using btrfs subvolumes with systemd

[Lennart Poettering]

On Thu, 09.06.16 20:30, Florent Peterschmitt (florent at peterschmitt.fr) wrote:

> # udevadm info /dev/mapper/root
> P: /devices/virtual/block/dm-0
> N: dm-0
> E: DEVNAME=/dev/dm-0
> E: DEVPATH=/devices/virtual/block/dm-0
> E: DEVTYPE=disk
> E: DM_UDEV_DISABLE_DISK_RULES_FLAG=1
> E: DM_UDEV_DISABLE_OTHER_RULES_FLAG=1
> E: DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG=1
> E: MAJOR=253
> E: MINOR=0
> E: SUBSYSTEM=block
> E: SYSTEMD_READY=0

So, the question is why this is set for your device. It could be set
for two reasons: because the DM rules decide so, or because the btrfs
rules decide so.

I am not a DM pro, so I am not going to comment on that, but if
it's the btrfs udev rules, then it would be this file:

/usr/lib/udev/rules.d/64-btrfs.rules

Which sets SYSTEMD_READY=0 in case the btrfs ioctls claim that the
device isn't ready yet to be mounted.

That said, I'd still bet the DM setup of yours is hosed, and the btrfs
stuff works fine. If the DM stuff would work correctly you'd have
properties like DM_NAME or DM_UUID on the device, but you do not.

Lennart

-- 
Lennart Poettering, Red Hat