zfs-mount.service WorkingDirectory ignored (Not an absolute path)

[LnxGnome]

System information

Type	Version/Name
Distribution Name	CentOS
Distribution Version	7.3
Linux Kernel	3.10.0-514.26.2
Architecture	x86_64
ZFS Version	0.7.0-1
SPL Version	0.7.0-1

Describe the problem you're observing

Seen in journalctl output:
systemd[1]: [/usr/lib/systemd/system/zfs-mount.service:14] Not an absolute path, ignoring: -/sbin/

Describe how to reproduce the problem

Install ZFS on CentOS 7.3 (this system was upgraded from 0.6.5)

other info

man systemd.exec
WorkingDirectory=
Takes an absolute directory path. Sets the working directory for executed processes. If not set, defaults to the root directory when systemd is running as a system instance and the respective user's home directory if run as user.

[loli10K]

https://www.freedesktop.org/software/systemd/man/systemd.exec.html#WorkingDirectory=

WorkingDirectory=

Takes a directory path relative to the service's root directory specified by RootDirectory=, or the special value "~ ". Sets the working directory for executed processes. If set to "~", the home directory of the user specified in User= is used. If not set, defaults to the root directory when systemd is running as a system instance and the respective user's home directory if run as user. If the setting is prefixed with the "-" character, a missing working directory is not considered fatal. If RootDirectory=/RootImage= is not set, then WorkingDirectory= is relative to the root of the system running the service manager. Note that setting this parameter might result in additional dependencies to be added to the unit (see above).

[loli10K]

This may be a systemd bug introduced in systemd/systemd@7b07e99.

@LnxGnome which systemd version is your system running?

[LnxGnome]

systemd-219-30.el7_3.9.x86_64

[loli10K]

Reproduced on CentOS7, cannot reproduce on Debian8 (systemd-215-17) or Sid (sytemd-234-2).

Also the "~" character doesn't seem to be accepted too:

centos systemd[1]: [/usr/lib/systemd/system/zfs-mount.service:15] Not an absolute path, ignoring: ~

Sorry but this doesn't seem a ZFS bug, maybe it's better to report this to your distro maintainer?

[LnxGnome]

Looks like that functionality was introduced into systemd @ systemd/systemd@5f5d8ea (Sep 23, 2015), which would make it part of the v227 release of systemd (Oct 7, 2015). CentOS is on v219, so it would not be present.

[loli10K]

@LnxGnome you're right, i had erroneously assumed CentOS had this functionality backported. Debian Jessie comes with systemd v215 but seems to support both "-" and "~".

[behlendorf]

Is there a simple proposed for the older versions of systemd.

[LnxGnome]

Don't set it. "If not set, defaults to the root directory when systemd is running as a system instance..."
Since ExecStart is an absolute path, is there a reason to set it to /sbin?

[behlendorf]

@LnxGnome this was done originally to work around some undesirable behavior in mount(8), commit d32d25c. We need to make sure the cwd is not root, in fact an empty directory would be best, to avoid a specific type of mount failure.

[LnxGnome]

Dropping the "-" is the next most straightforward solution. /sbin should be there.
@sbindir@ might be an alternative, which from the rpm.spec is /sbin.
If you leave it as-is, then (has error, defaults to back /) doesn't that reintroduce the chance of undesirable behavior that d32d25c is supposed to avoid?