[systemd-devel] Syntax check for a new service?

[Mantas Mikulėnas]

On Sat, Feb 26, 2022 at 7:05 PM Tom Browder <tom.browder at gmail.com> wrote:

> On Sat, Feb 26, 2022 at 09:38 Dave Howorth <systemd at howorth.org.uk> wrote:
>
>> On Sat, 26 Feb 2022 09:17:38 -0600
>> Tom Browder <tom.browder at gmail.com> wrote:
>> > Is there any way to get a plain syntax check of a potential new
>> > service file?
>>
>> systemd-analyze verify FILE...
>
>
> Thanks, Dave.
>
> I'm apparently having problems with the executable file and I'm not sure
> if I need
> the Type to be simple or oneshot.
>
> The service I'm trying to create is to emulate a user at the CLI executing
> a script running in the foreground who never logs out.
>
> The script loops infinitely listening and responding to a specific port
> behind an apache reverse proxy. The script is programmed to stop with a
> Ctr-C. It can be left with "nohup &" (but I'm not sure if that interferes
> with its design yet).
>

Right, that's basically how all services work. (It's not really something I
would call "emulating a user" – that just feels backwards. It's more like
*the user* with 'nohup' is emulating a service manager here...)

If the service remains running in foreground, it's Type=simple. (Services
which go into background, i.e. have a 'daemonize' function, would be
Type=forking.)

Type=oneshot is for "one-shot" tasks which do something relatively quick
and exit; for example, if another unit had "After=an-oneshot.service", it
would wait until that service *exits,* rather than until it's "started".
It's not suitable for actual long-running services like yours – if you
tried to use Type=oneshot, systemd would think your service was "starting"
forever.


>
> I do know I have to set an environment variable for the executable to find
> its libraries, and I'm not sure how to do that in the service file to
> emulate this:
>
>     export MYLIB=/path/to/lib; /path/to/prog
>
> I have tried both Type=oneshot and Type=simple but neither like the single
> ExecStart= line with that command.
>

Neither of them invoke /bin/sh to parse the command – the *shell* is what
normally would interpret the "export ..." in a shell script, but that
doesn't happen in systemd services. In all cases, ExecStart is minimally
parsed by systemd itself and then just directly execve()'d.

Use the Environment= option to set environment variables.

-- 
Mantas Mikulėnas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20220226/b802f411/attachment.htm>