[systemd-devel] How to handle loop mounts?

[Eelco Dolstra]

Hi,

On 08/08/12 08:24, Mike Kazantsev wrote:

>> I have an /etc/fstab that contains the following line:
>>
>>   /disk1.img /disk1 ext4 loop 0 2
>>
>> where /disk1.img is a regular file containing an ext4 filesystem.  Systemd fails
>> to mount /disk1 if I run "systemctl start disk1.mount":
>>
> ...
> 
> Same thing seem to work here:
> 
>   dd if=/dev/zero of=looptest bs=1M count=100 
>   losetup /dev/loop0 looptest
>   mkfs.ext4 /dev/loop0
>   losetup -D
>   echo '/root/looptest /mnt/tmp ext4 loop' >>/etc/fstab

Ah!  This did work.  It turns out that the problem is actually caused by having
a non-zero fs_passno field in /etc/fstab.  I.e.

  /disk1.img /disk1 ext4 loop 0 0

works, while

  /disk1.img /disk1 ext4 loop 0 2

hangs because systemd adds a dependency on systemd-fsck at disk1.img.service, which
in turn has a dependency on the non-existent disk1.img.device.

Now for this ext4 example I can live without running fsck, but in general loop
filesystems may require fsck.  Any ideas on how to fix this?

Also, there doesn't seem to be a workaround for using loop devices with
crypttab.  Example:

$ dd if=/dev/zero of=/disk2.img bs=1M count=100
$ cryptsetup luksFormat /disk2.img
...
$ echo 'crypted /disk2.img - timeout=60' > /etc/crypttab
$ systemctl daemon-reload
$ systemctl start cryptsetup.target
(hangs)
$ systemctl list-jobs --full
 JOB UNIT                      TYPE            STATE
8534 cryptsetup.target         start           waiting
8535 systemd-cryptsetup at crypted.service start           waiting
8538 disk2.img.device          start           running
8539 dev-mapper-crypted.device start           running
$ journalctl
...
Aug 08 15:33:51 machine systemd[1]: Job disk2.img.device/start timed out.
Aug 08 15:33:51 machine systemd[1]: Job cryptsetup.target/start failed with
result 'dependency'.
...

(I'm running systemd 187 BTW.)

-- 
Eelco Dolstra | LogicBlox, Inc. | http://nixos.org/~eelco/