systemd

Recharge / redémarre systemd :

$ systemctl daemon-reload
$ systemctl daemon-reexec

Affiche la liste des dépendances d'une unité :

$ systemctl list-dependencies nfs-client.target
nfs-client.target
● ├─auth-rpcgss-module.service
● ├─rpc-statd-notify.service
● └─remote-fs-pre.target

Afficher une propriété d'un service :

$ systemctl show -p "Wants" nfs.service 
Wants=rpcbind.socket network-online.target auth-rpcgss-module.service rpc-statd-notify.service nfs-config.service rpc-statd.service nfs-idmapd.service

Liste l'arbre des cgroups :

$ systemd-cgls

Affiche les uités :

$ systemctl list-unit-files --type=mount  
UNIT FILE                     STATE    
-.mount                       generated
boot-efi.mount                generated
dev-hugepages.mount           static   
dev-mqueue.mount              static   
home.mount                    generated
proc-fs-nfsd.mount            static   
proc-sys-fs-binfmt_misc.mount static   
sys-fs-fuse-connections.mount static   
sys-kernel-config.mount       static   
sys-kernel-debug.mount        static   
tmp.mount                     static   
var-lib-machines.mount        static   
var-lib-nfs-rpc_pipefs.mount  static   

13 unit files listed.

$ systemctl list-unit-files --state=generated
UNIT FILE            STATE    
-.mount              generated
boot-efi.mount       generated
home.mount           generated
livesys-late.service generated
livesys.service      generated
netconsole.service   generated
network.service      generated

7 unit files listed.

Modifie un service existant ou en crée un nouveau :

$ sudo systemctl edit crond.service
$
$ #Liste edite le service et recopiant le père
$ sudo systemctl edit crond.service -l
$ sudo systemctl edit crond.service -full

Date pour timer :

Minimal form                   Normalized form
Sat,Thu,Mon-Wed,Sat-Sun    ==> Mon-Thu,Sat,Sun *-*-* 00:00:00
Mon,Sun 12-*-* 2,1:23      ==> Mon,Sun 2012-*-* 01,02:23:00
Wed *-1                    ==> Wed *-*-01 00:00:00
Wed-Wed,Wed *-1            ==> Wed *-*-01 00:00:00
Wed, 17:48                 ==> Wed *-*-* 17:48:00
Wed-Sat,Tue 12-10-15 1:2:3 ==> Tue-Sat 2012-10-15 01:02:03
*-*-7 0:0:0                ==> *-*-07 00:00:00
10-15                      ==> *-10-15 00:00:00
monday *-12-* 17:00        ==> Mon *-12-* 17:00:00
Mon,Fri *-*-3,1,2 *:30:45  ==> Mon,Fri *-*-01,02,03 *:30:45
12,14,13,12:20,10,30       ==> *-*-* 12,13,14:10,20,30:00
mon,fri *-1/2-1,3 *:30:45  ==> Mon,Fri *-01/2-01,03 *:30:45
03-05 08:05:40             ==> *-03-05 08:05:40
08:05:40                   ==> *-*-* 08:05:40
05:40                      ==> *-*-* 05:40:00
Sat,Sun 12-05 08:05:40     ==> Sat,Sun *-12-05 08:05:40
Sat,Sun 08:05:40           ==> Sat,Sun *-*-* 08:05:40
2003-03-05 05:40           ==> 2003-03-05 05:40:00
2003-03-05                 ==> 2003-03-05 00:00:00
03-05                      ==> *-03-05 00:00:00
hourly                     ==> *-*-* *:00:00
daily                      ==> *-*-* 00:00:00
monthly                    ==> *-*-01 00:00:00
weekly                     ==> Mon *-*-* 00:00:00
*:20/15                    ==> *-*-* *:20/15:00

Some other options like OnCalendar are available :

OnActiveSec defines a timer relative to the moment the timer itself is activated.
OnBootSec defines a timer relative to when the machine was booted up.
OnStartupSec defines a timer relative to when systemd was started.
OnUnitActiveSec defines a timer relative to when the unit the timer is activating was last activated.
OnUnitInactiveSec defines a timer relative to when the unit the timer is activating was last deactivated.

Exemple :

[Unit]
Description=Execute backup every day at midnight

[Timer]
OnCalendar=*-*-* 00:00:00
Unit=backup.service

[Install]
WantedBy=multi-user.target

2 moyens d'activer les processus persistants (qui continue après la fermeture de session) :
- loginctl enable-linger [user] : Active les processus persistant pour le user donné (si pas de user alors user courant). L'utilisateur peut alors utiliser la commande systemd-run pour lancer un process persistant, par exemple :systemd-run –scope –user /usr/bin/screen
- Dans le fichier /etc/systemd/logind.conf, définissez KillUserProcesses=no pour activer les processus persistant sur tout le système