[systemd-devel] [Install] section of symlinked unit file ignored if drop-in file is used

[林自均]

Hi John,

I'm not sure whether this issue is because of
https://github.com/systemd/systemd/pull/7158 or not. I will figure it out.
Thanks.

John Lin

John Gallagher <john.gallagher at delphix.com> 於 2018年5月24日 週四 上午8:07寫道：

> If I have a unit file for a service that lives off the unit file
> search path, I can link it, and then enable it using the service name
> instead of the full path of the unit file:
>
> $ cat foo.service
> [Service]
> Type=simple
> ExecStart=/bin/sleep 100000000
>
> [Install]
> WantedBy=multi-user.target
> $ sudo systemctl link ~/foo.service
> Created symlink /etc/systemd/system/foo.service →
> /export/home/delphix/foo.service.
> $ sudo systemctl enable foo
> Created symlink
> /etc/systemd/system/multi-user.target.wants/foo.service →
> /export/home/delphix/foo.service.
>
> If I add a drop-in file for the service though, enabling the service
> using the service name does not behave the same way:
>
> $ cat /etc/systemd/system/foo.service.d/env.conf
> [Service]
> Environment=FOO=bar
> $ sudo systemctl enable foo
> The unit files have no installation config (WantedBy, RequiredBy, Also,
> Alias
> settings in the [Install] section, and DefaultInstance for template units).
> This means they are not meant to be enabled using systemctl.
> Possible reasons for having this kind of units are:
> 1) A unit may be statically enabled by being symlinked from another unit's
>    .wants/ or .requires/ directory.
> 2) A unit's purpose may be to act as a helper for some other unit which has
>    a requirement dependency on it.
> 3) A unit may be started when needed via activation (socket, path, timer,
>    D-Bus, udev, scripted systemctl call, ...).
> 4) In case of template units, the unit is meant to be enabled with some
>    instance name specified.
>
> I get the warning above, and the expected link in
> /etc/systemd/system/multi-user.target.wants/ is not created. I can
> work around this behavior by doing the enable using the path of the
> unit file:
>
> $ sudo systemctl enable ~/foo.service
> Created symlink
> /etc/systemd/system/multi-user.target.wants/foo.service →
> /export/home/delphix/foo.service.
>
> The [Install] section of the unit file being ignored or respected
> based on the presence or absence of a drop-in file seems inconsistent
> to me, but I am fairly new to systemd, so I may be missing something.
> Is this behavior expected?
>
> Thanks,
> John
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