zibaldone:linux:systemd [Galileo Labs]

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====== Systemd ======

<code>
systemctl status
</code>

show running units
<code>
systemctl
</code>

show available unit files
<code>
systemctl list-unit-files
</code>

enable unit
<code>
systemctl enable name.service
</code>

start unit
<code>
systemctl start name
</code>

after change unit file
<code>
systemctl daemon-reload
</code>

===== Systemd as user =====

enable systemd for specific user
<code>
loginctl enable-linger <username>
</code>

  * add user to systemd-journal group to permit journactl operations
<code>
usermod -a -G systemd-journal <user>
</code>

  * modify /etc/systemd/journald.conf
<code>
[Journal]
Storage=persistent
</code>


deprecated
<file bash /etc/profile.d/systemd-user.sh>
export XDG_RUNTIME_DIR="/run/user/$UID"
export DBUS_SESSION_BUS_ADDRESS="unix:path=${XDG_RUNTIME_DIR}/bus"
</file>

new method
<code>
mkdir -p ~/.bashrc.d
echo "export XDG_RUNTIME_DIR=/run/user/$(id -u)" > ~/.bashrc.d/systemd 
source ~/.bashrc.d/systemd
</code>
journalctl -u does not work. Use instead
<code>
journalctl --user --user-unit
</code>

===== Systemd Timer =====

Una valida e più potente alternativa a cron, integrata in systemd, è rappresentata dai timers, di primo impatto soprattutto nell'aspetto supervisivo tramite journalctl, ma non solo (vedi risposta a questo quesito http://unix.stackexchange.com/questions/278564/cron-vs-systemd-timers).

Per attivare un timer servono essenzialmente due cose:

  * Il timer: /etc/systemd/system/nms-restart.timer
<code>
[Unit]
Description=Perform a nms resrtart

[Timer]
OnCalendar=hourly

[Install]
WantedBy=timers.target
</code>

  * il servizio: /etc/systemd/system/nms-restart.service

<code>
[Unit]
Description=Perform a nms restart

[Service]
Type=simple
Nice=19
IOSchedulingClass=2
IOSchedulingPriority=7
ExecStart=/usr/local/sbin/nms-restart
</code>

Poi si avvia e abilita il timer:
<code>
sudo systemctl start nms-restart.timer
sudo systemctl enable nms-restart.timer
</code>

Per la lista dei timer
<code>
systemctl list-timers --all
</code>

Per monitorare si usa journalctl in tutte le sue forme, per esempio:
<code>
journalctl -f -u nms-restart
</code>