[systemd-devel] mount units and automatic (un)mounts

[Andrei Borzenkov]

15.07.2016 19:50, Alad Wenter пишет:
...

>>
>>> "systemctl reset-failed" is issued (note that appending the .mount unit
>>> doesn't work in this case, giving a "Unit mnt-transcend\x2dsdhc.mount is
>>> not loaded" error).
>>>
>> So how exactly do you call it?
> % sudo systemctl reset-failed mnt-transcend\x2dsdhc.mount
> Failed to reset failed state of unit mnt-transcendx2dsdhc.mount: Unit
> mnt-transcendx2dsdhc.mount is not loaded.
> 

Sorry if I was not clear. You said this did not work, implying some
other invocation did. If "appending .mount unit does not work", I expect
some other command that *does* work?

> Being now aware of the distinction between in-memory and static units, I
> assume this is due to mnt-transcend\x2dsdhc.mount being in-memory? The
> reset-failed command works as expected with .mount units which are on disk.

Well, if this mount unit was instantiated from /proc/self/mountinfo,
then goes away then of course systemd does not know anything about it
any more.

...

>>> [Service]
>>> Type=oneshot
>>> RemainAfterExit=yes
>>> ExecStart=/bin/mount -a -t nocifs,nosmbfs,nonfs
>>>
>>> [Install]
>>> WantedBy=local-fs.target
>>>
>>> However, according to the systemd.mount(5), .mount units will be
>>> generated either way. Oddly enough, when using the above service they
>>> don't seem to cause automatic mounts/unmounts.
>>>
>> Because in this case you do not have static mount units, and for
>> transient mount units (created from external mount event) things were
>> partially fixed by not requiring existing device.
> Could you give a pointer on what release this was partially fixed in? In
> the NEWS file, I only found a mention to systemd 219 which introduced
> unmounting of unavailable devices.

I mean this commit

commit 628c89cc68ab96fce2de7ebba5933725d147aecc
Author: Lennart Poettering <lennart at poettering.net>
Date:   Fri Feb 27 21:55:08 2015 +0100

    core: rework device state logic

    This change introduces a new state "tentative" for device units. Device
    units are considered "plugged" when udev announced them, "dead" when
    they are not available in the kernel, and "tentative" when they are
    referenced in /proc/self/mountinfo or /proc/swaps but not (yet)
    announced via udev.

    This should fix a race when device nodes (like loop devices) are created
    and immediately mounted. Previously, systemd might end up seeing the
    mount unit before the device, and would thus pull down the mount because
    its BindTo dependency on the device would not be fulfilled.


with lot of subsequent fixes ... this commit is included starting with v220.