[systemd-devel] Problems trying to convert a System-V-Init script to systemd

[Holger Kiehl]

On Thu, 14 Jul 2016, Andrei Borzenkov wrote:

> 14.07.2016 15:34, Holger Kiehl пишет:
> > Hello,
> > 
> > I am new to systemd and the maintainer of the file distribution software
> > AFD (http://www.dwd.de/AFD) and I am trying to adapt this application
> > to systemd. The problem I am unable to solve is that doing a reboot,
> > poweroff or halt, all process get a SIGTERM before systemd calls the
> > command supplied by ExecStop. If I do a 'systemctl stop afd.service'
> > everything works as expected. I have searched the web for a solution
> > and have tried all the different service Type=, unit After=/Before=
> > combination, but failed so far. I must be doing something obviously
> > wrong, but unable to see what and need help please.
> > 
> > The service/unit file looks as follows:
> > 
> >    [Unit]
> >    Description=Automatic File Distributor
> >    After=basic.target
> > 
> 
> This is redundant - it is default for any standard service
> 
> >    [Service]
> >    RemainAfterExit=yes
> >    Type=oneshot
> 
> That's wrong (although it is unrelated to the problem you have). It
> means systemd expects ExecStart to run and finish. In your case it
> appears to work because you use RemainAfterExit, but if you look more
> closely, your service is in state where PID is exited.
> 
> >    ExecStart=-/etc/init.d/afd start
> >    ExecStop=-/etc/init.d/afd stop
> >    KillMode=none
> 
> Well, in this case you rely on your service to behave well. You must be
> very confident :)
> 
> >    StandardOutput=syslog+console
> >    StandardError=syslog+console
> > 
> >    [Install]
> >    WantedBy=multi-user.target
> > 
> > /etc/init.d/afd is a shell script that starts one or more instances of
> 
> If you start multiple instances, you should consider service template so
> each instance can be represented as exactly one systemd service.
> 
> > the AFD under different users. The users are configured in /etc/sysconfig/afd
> > and are started via the following command: su - $afduser -c "<cmd start/sop AFD>"
> 
> so what most likely happens, is - su establishes new login session; on
> shutdown these sessions are cleaned up (concurrently with any running
> service - unfortunately, there is no way to express dependency between
> user and system systemd instances). Here is where you get your signals.
> 
> Check with loginctl after service is started - do you see and extra seesion?
> 
> > To speed things up a bit the script forks for each user to start/stop the
> > AFD instances. The script /etc/init.d/afd is just initiating thinks, but
> > always waits for the command to complete. AFD itself has an init process
> > (init_afd) that then starts several other process and monitors them.
> > 
> > In /etc/init.d/afd I have added the following line in the beginning, before
> > it wants to do the shutdown:
> > 
> >    echo "Before: ps -u afd: `ps -u $afduser`" >> /var/log/afd.log
> > 
> > And this then shows the following:
> > 
> >    Before: ps -u afd:   PID TTY          TIME CMD
> >     1258 ?        00:00:00 init_afd
> >     1260 ?        00:00:00 system_log <defunct>
> >     1261 ?        00:00:00 event_log <defunct>
> >     1262 ?        00:00:00 receive_log <defunct>
> >     1263 ?        00:00:00 transfer_log <defunct>
> >     1264 ?        00:00:00 trans_db_log <defunct>
> >     1265 ?        00:00:00 archive_watch <defunct>
> >     1266 ?        00:00:00 input_log <defunct>
> >     1267 ?        00:00:00 output_log <defunct>
> >     1268 ?        00:00:00 delete_log <defunct>
> >     1269 ?        00:00:00 production_log <defunct>
> >     1270 ?        00:00:00 distribution_lo <defunct>
> >     1271 ?        00:00:00 amg <defunct>
> >     1272 ?        00:00:00 aldad <defunct>
> >     1287 ?        00:00:00 afd_stat <defunct>
> >     1288 ?        00:00:00 fd <defunct>
> >     1289 ?        00:00:00 dir_check <defunct>
> > 
> > All the process have received a SIGTERM before (or during the execution)
> > of the script.
> > 
> > Any idea what I am doing wrong,
> 
> Much :)
> 
> > or what else I can try to do a proper
> > shutdown of this application under systemd?
> >
> 
> Use native systemd unit, do not use init scripts. Use User= to
> impersonate user, use Type=forking and PIDFile= to proper synchronize
> service startup, use templates to run multiple instances.
> 
First thank you very much for your very clear and good explaination.

I tried to avoid Type=forking and PIDFile= because I then have to maintain
two different init versions, systemd and System-V-Init. I think there will
always be other Unix systems around without systemd and I do not want to
loose those users.

Would it help if I build into my script for each instant it starts
it calls systemd-notify with --pid=<init_afd pid of the user>? But if
I understand you correctly this too would not help because of the 'su -'.
Correct?

Regards,
Holger