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diff --git a/nixos/doc/manual/administration/service-mgmt.xml b/nixos/doc/manual/administration/service-mgmt.xml new file mode 100644 index 000000000000..c0940a42f307 --- /dev/null +++ b/nixos/doc/manual/administration/service-mgmt.xml @@ -0,0 +1,83 @@ +<chapter xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink" + xmlns:xi="http://www.w3.org/2001/XInclude" + version="5.0" + xml:id="sec-systemctl"> + +<title>Service Management</title> + +<para>In NixOS, all system services are started and monitored using +the systemd program. Systemd is the “init” process of the system +(i.e. PID 1), the parent of all other processes. It manages a set of +so-called “units”, which can be things like system services +(programs), but also mount points, swap files, devices, targets +(groups of units) and more. Units can have complex dependencies; for +instance, one unit can require that another unit must be successfully +started before the first unit can be started. When the system boots, +it starts a unit named <literal>default.target</literal>; the +dependencies of this unit cause all system services to be started, +file systems to be mounted, swap files to be activated, and so +on.</para> + +<para>The command <command>systemctl</command> is the main way to +interact with <command>systemd</command>. Without any arguments, it +shows the status of active units: + +<screen> +$ systemctl +-.mount loaded active mounted / +swapfile.swap loaded active active /swapfile +sshd.service loaded active running SSH Daemon +graphical.target loaded active active Graphical Interface +<replaceable>...</replaceable> +</screen> + +</para> + +<para>You can ask for detailed status information about a unit, for +instance, the PostgreSQL database service: + +<screen> +$ systemctl status postgresql.service +postgresql.service - PostgreSQL Server + Loaded: loaded (/nix/store/pn3q73mvh75gsrl8w7fdlfk3fq5qm5mw-unit/postgresql.service) + Active: active (running) since Mon, 2013-01-07 15:55:57 CET; 9h ago + Main PID: 2390 (postgres) + CGroup: name=systemd:/system/postgresql.service + ├─2390 postgres + ├─2418 postgres: writer process + ├─2419 postgres: wal writer process + ├─2420 postgres: autovacuum launcher process + ├─2421 postgres: stats collector process + └─2498 postgres: zabbix zabbix [local] idle + +Jan 07 15:55:55 hagbard postgres[2394]: [1-1] LOG: database system was shut down at 2013-01-07 15:55:05 CET +Jan 07 15:55:57 hagbard postgres[2390]: [1-1] LOG: database system is ready to accept connections +Jan 07 15:55:57 hagbard postgres[2420]: [1-1] LOG: autovacuum launcher started +Jan 07 15:55:57 hagbard systemd[1]: Started PostgreSQL Server. +</screen> + +Note that this shows the status of the unit (active and running), all +the processes belonging to the service, as well as the most recent log +messages from the service. + +</para> + +<para>Units can be stopped, started or restarted: + +<screen> +$ systemctl stop postgresql.service +$ systemctl start postgresql.service +$ systemctl restart postgresql.service +</screen> + +These operations are synchronous: they wait until the service has +finished starting or stopping (or has failed). Starting a unit will +cause the dependencies of that unit to be started as well (if +necessary).</para> + +<!-- - cgroups: each service and user session is a cgroup + +- cgroup resource management --> + +</chapter> |