[systemd-devel] What if a service is started manually
In a trial presentation I used the following service file: [Unit] Description=Virtual Distributed Ethernet After=syslog.target [Service] Type=forking PIDFile=/var/run/vde.pid # Note the -f: don't fail if there is no PID file ExecStartPre=/bin/rm -f /var/run/vde.pid ExecStart=/usr/bin/vde_switch --tap tap0 --mode 0660 \ --dirmode 0750 --group qemu \ --daemon --pidfile /var/run/vde.pid Restart=on-abort [Install] WantedBy=multi-user.target Here the PID file is removed before the service is started. This brought up two questions. - What happens is you start a service that you already started? Nothing, or is the service first stopped and then again started? - What happens if someone started the service manually? So bypassing systemd and running directly /usr/bin/vde_switch. Met vriendelijke groet, Cecil Westerhof Engineer mobiel +31 - 6 - 25 00 38 81 -- Snow B.V. Unix Specialists De Ooyen 11 4191 PB Geldermalsen http://www.snow.nl tel. +31 - 345 - 65 66 66 ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] What if a service is started manually
On 11/29/2013 12:23 AM, Cecil Westerhof wrote: In a trial presentation I used the following service file: [Unit] Description=Virtual Distributed Ethernet After=syslog.target [Service] Type=forking PIDFile=/var/run/vde.pid # Note the -f: don't fail if there is no PID file ExecStartPre=/bin/rm -f /var/run/vde.pid ExecStart=/usr/bin/vde_switch --tap tap0 --mode 0660 \ --dirmode 0750 --group qemu \ --daemon --pidfile /var/run/vde.pid Restart=on-abort [Install] WantedBy=multi-user.target Here the PID file is removed before the service is started. This brought up two questions. - What happens is you start a service that you already started? Nothing, or is the service first stopped and then again started? - What happens if someone started the service manually? So bypassing systemd and running directly /usr/bin/vde_switch. I was not clear here. What I mend: someone starts the service manually and after this starts the service with systemctl. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] What if a service is started manually
On Nov 29, 2013 1:36 AM, Cecil Westerhof cecil.wester...@snow.nl wrote: Thanks for the speedy reply. On 11/29/2013 12:30 AM, Mantas Mikulėnas wrote: On Nov 29, 2013 1:24 AM, Cecil Westerhof cecil.wester...@snow.nl mailto:cecil.wester...@snow.nl wrote: In a trial presentation I used the following service file: [Unit] Description=Virtual Distributed Ethernet After=syslog.target [Service] Type=forking PIDFile=/var/run/vde.pid # Note the -f: don't fail if there is no PID file ExecStartPre=/bin/rm -f /var/run/vde.pid ExecStart=/usr/bin/vde_switch --tap tap0 --mode 0660 \ --dirmode 0750 --group qemu \ --daemon --pidfile /var/run/vde.pid Restart=on-abort [Install] WantedBy=multi-user.target Here the PID file is removed before the service is started. This brought up two questions. - What happens is you start a service that you already started? Nothing, or is the service first stopped and then again started? 'systemctl start' only starts services, therefore it will do nothing if the service is already started. 'systemctl restart' would stop it and start it again. - What happens if someone started the service manually? So bypassing systemd and running directly /usr/bin/vde_switch. As far as systemd is concerned, nothing happens - the manually started vde_switch is just another process inside your login session. It will *not* be automatically pulled into a service just because the program name or something happens to match... I should learn to ask my questions better. T_T What I mend to ask. Someone starts /usr/bin/vde_switch manually and after that uses systemctl to start it. If the second vde_switch instance is configured to listen on the same sockets, etc., then... Well, it depends on the daemon itself: * most will consider this a fatal error, and exit with non-zero status, causing the systemd .service to fail as well; * but some will think that the existing socket is stale, will remove it, and happily start on top of the first instance. (Only happens with Unix sockets, of course; if the daemon uses TCP or tries to grab the same 'tap0' interface or such, then it can only fail.) I don't know how vde behaves. It will probably refuse to start. The best way to find out, of course, is to try systemd yourself. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] What if a service is started manually
On 11/29/2013 12:59 AM, Mantas Mikulėnas wrote: In a trial presentation I used the following service file: [Unit] Description=Virtual Distributed Ethernet After=syslog.target [Service] Type=forking PIDFile=/var/run/vde.pid # Note the -f: don't fail if there is no PID file ExecStartPre=/bin/rm -f /var/run/vde.pid ExecStart=/usr/bin/vde_switch --tap tap0 --mode 0660 \ --dirmode 0750 --group qemu \ --daemon --pidfile /var/run/vde.pid Restart=on-abort [Install] WantedBy=multi-user.target Here the PID file is removed before the service is started. This brought up two questions. - What happens is you start a service that you already started? Nothing, or is the service first stopped and then again started? 'systemctl start' only starts services, therefore it will do nothing if the service is already started. 'systemctl restart' would stop it and start it again. - What happens if someone started the service manually? So bypassing systemd and running directly /usr/bin/vde_switch. As far as systemd is concerned, nothing happens - the manually started vde_switch is just another process inside your login session. It will *not* be automatically pulled into a service just because the program name or something happens to match... I should learn to ask my questions better. T_T What I mend to ask. Someone starts /usr/bin/vde_switch manually and after that uses systemctl to start it. If the second vde_switch instance is configured to listen on the same sockets, etc., then... Well, it depends on the daemon itself: * most will consider this a fatal error, and exit with non-zero status, causing the systemd .service to fail as well; * but some will think that the existing socket is stale, will remove it, and happily start on top of the first instance. (Only happens with Unix sockets, of course; if the daemon uses TCP or tries to grab the same 'tap0' interface or such, then it can only fail.) I don't know how vde behaves. It will probably refuse to start. The best way to find out, of course, is to try systemd yourself. I need only a generic answer. So if this question is asked I can answer with it depends on the service. Making sure that when they ask further I remember your explanation. Thanks. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] What if a service is started manually
On Fri, 29.11.13 00:23, Cecil Westerhof (cecil.wester...@snow.nl) wrote: In a trial presentation I used the following service file: [Unit] Description=Virtual Distributed Ethernet After=syslog.target In curretn systemd versions the After=syslog.target is unnecessary. [Service] Type=forking PIDFile=/var/run/vde.pid # Note the -f: don't fail if there is no PID file ExecStartPre=/bin/rm -f /var/run/vde.pid ExecStart=/usr/bin/vde_switch --tap tap0 --mode 0660 \ --dirmode 0750 --group qemu \ --daemon --pidfile /var/run/vde.pid Restart=on-abort [Install] WantedBy=multi-user.target Here the PID file is removed before the service is started. This brought up two questions. - What happens is you start a service that you already started? Nothing, or is the service first stopped and then again started? A started service is unaffected by yet another start request. If two clients request the same service to start and wait for it to complete, then the two start jobs are coalesced and only one instance is started with both clients waiting for the startup of that same instance to finish. - What happens if someone started the service manually? So bypassing systemd and running directly /usr/bin/vde_switch. If you start things on the shell, then systemd won't know about it. It's exactly the same as if you ran the daemon binary twice on a classic sysvinit system: it's up to the daemon how it deals with that. Most daemons will check for PID files and refuse starting twice... Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
