Latest revision as of 16:30, 21 November 2024

Documentation

Locations

/etc/systemd
/usr/lib/systemd/
/lib/systemd

HOWTO

systemctl verbose

SYSTEMD_LOG_LEVEL=debug systemctl start yourservice

Services

List enabled services

See https://www.baeldung.com/linux/systemctl-list-enabled-services

systemctl list-unit-files --state=enabled

Edit systemd service file

systemctl edit --full my.service

Timers

https://opensource.com/article/20/7/systemd-timers
https://wiki.archlinux.org/title/Systemd/Timers
https://linuxhint.com/cron_systemd_timer/ also about random time

man systemd.timer

List active timers

systemctl list-timers

List all timers

systemctl list-timers --all

Enable timer

systemctl enable fstrim.timer

Auto restart crashed services

systemctl edit elasticsearch.service

add:

[Service]
Restart=always

then

systemctl daemon-reload
systemctl restart elasticsearch.service

And to get an email when service gets restarted: https://dev.to/setevoy/linux-systemd-unit-files-edit-restart-on-failure-and-email-notifications-5h3k

Logs

View systemd logs

journalctl -u postfix

FAQ

Analyze boot processes

systemd-analyze blame

gateway4 has been deprecated

Using routes:

routes:
- to: default
  via: 192.168.1.1

Systemd and DNS

resolvectl status

Change nameserversers resolvectl uses

On Ubuntu

Edit the netplan file

netplan generate
netplan apply

Failed to get global data: Unit dbus-org.freedesktop.resolve1.service not found.

Means systemd-resolved is not running

Restart:

systemctl restart systemd-resolved

Add nameserver

Sacrifice a chicken

Flush caches

thing from the past?

systemd-resolve --flush-caches

All status

systemctl status -a

syslog spam

https://psyq123.wordpress.com/2015/06/29/if-you-get-a-lot-of-logspam-from-systemd-in-your-varlogsyslog-this-might-help/

list available services

systemctl list-unit-files

or

systemctl list-units

normal interface names

net.ifnames=0

Show failed services

systemctl --failed

systemd: Started Session

Change loglevel to notice in /etc/systemd/system.conf

systemctl daemon-reexec

Status

Active: inactive (dead)

parameter ActiveState would return inactive

SubState returns dead

@@ Line 1: / Line 1: @@
-=Documentation=
-*http://www.freedesktop.org/wiki/Software/systemd/
-*https://wiki.ubuntu.com/systemd
-*https://wiki.ubuntu.com/SystemdForUpstartUsers
-*[https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units How To Use Systemctl to Manage Systemd Services and Units]
-*[http://xmodulo.com/switch-from-networkmanager-to-systemd-networkd.html How to switch from NetworkManager to systemd-networkd on Linux]
-*https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet
-*[https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/ Predictable Network Interface Names]
-=Locations=
+&nbsp;
+= Documentation =
+*[https://www.dynacont.net/documentation/linux/Useful_SystemD_commands/ Useful systemd commands]
+*[http://www.freedesktop.org/wiki/Software/systemd/ http://www.freedesktop.org/wiki/Software/systemd/]
+*[https://wiki.ubuntu.com/systemd https://wiki.ubuntu.com/systemd]
+*[https://wiki.archlinux.org/index.php/Systemd Creating systemd service]
+*[https://wiki.ubuntu.com/SystemdForUpstartUsers https://wiki.ubuntu.com/SystemdForUpstartUsers]
+*[https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units How To Use Systemctl to Manage Systemd Services and Units]
+*[http://xmodulo.com/switch-from-networkmanager-to-systemd-networkd.html How to switch from NetworkManager to systemd-networkd on Linux]
+*[https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet]
+*[https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/ Predictable Network Interface Names]
+*[[https://blog.darknedgy.net/technology/2020/05/02/0/index.html#tech-critique https://blog.darknedgy.net/technology/2020/05/02/0/index.html#tech-critique]
+*[https://mohsensy.github.io/sysadmin/2018/08/19/systemd-service-tutorial.html Systemd service tutorial]
+*[https://www.freedesktop.org/wiki/Software/systemd/dbus/ https://www.freedesktop.org/wiki/Software/systemd/dbus/ Systemd and dbus]
+*[https://www.thegeekdiary.com/how-to-boot-into-rescue-mode-or-emergency-mode-through-systemd-in-centos-rhel-7-and-8/ Single user/emergency]
+= Locations =
   /etc/systemd
   /usr/lib/systemd/
+ /lib/systemd
+&nbsp;
-=FAQ=
+= HOWTO =
-==syslog spam==
+==systemctl verbose==
-https://psyq123.wordpress.com/2015/06/29/if-you-get-a-lot-of-logspam-from-systemd-in-your-varlogsyslog-this-might-help/
+ SYSTEMD_LOG_LEVEL=debug systemctl start yourservice
+==Services==
+===List enabled services===
+See https://www.baeldung.com/linux/systemctl-list-enabled-services
+ systemctl list-unit-files --state=enabled
+===Edit systemd service file===
+ systemctl edit --full my.service
+== Timers ==
+*[https://opensource.com/article/20/7/systemd-timers https://opensource.com/article/20/7/systemd-timers]
+*[https://wiki.archlinux.org/title/Systemd/Timers https://wiki.archlinux.org/title/Systemd/Timers]
+*https://linuxhint.com/cron_systemd_timer/ also about random time
+ man systemd.timer
+=== List active timers ===
+ systemctl list-timers
+=== List all timers ===
+ systemctl list-timers --all
+=== Enable timer ===
+ systemctl enable fstrim.timer
+== Auto restart crashed services ==
+ systemctl edit elasticsearch.service
+add:
+ [Service]
+ Restart=always
+then
+ systemctl daemon-reload
+ systemctl restart elasticsearch.service
+And to get an email when service gets restarted: https://dev.to/setevoy/linux-systemd-unit-files-edit-restart-on-failure-and-email-notifications-5h3k
+==Logs==
+===View systemd logs===
+ journalctl -u postfix
+= FAQ =
+== Analyze boot processes ==
+ systemd-analyze blame
+== gateway4 has been deprecated ==
+Using routes:
+ routes:
+ - to: default
+   via: 192.168.1.1
+== Systemd and DNS ==
+ resolvectl status
+===Change nameserversers resolvectl uses===
+====On Ubuntu====
+Edit the netplan file
+ netplan generate
+ netplan apply
+=== Failed to get global data: Unit dbus-org.freedesktop.resolve1.service not found. ===
+Means systemd-resolved is not running
+Restart:
+ systemctl restart systemd-resolved
+&nbsp;
+=== Add nameserver ===
+Sacrifice a chicken
+&nbsp;
+=== Flush caches ===
+# thing from the past?
+ systemd-resolve --flush-caches
+== All status ==
+ systemctl status -a
+== syslog spam ==
+[https://psyq123.wordpress.com/2015/06/29/if-you-get-a-lot-of-logspam-from-systemd-in-your-varlogsyslog-this-might-help/ https://psyq123.wordpress.com/2015/06/29/if-you-get-a-lot-of-logspam-from-systemd-in-your-varlogsyslog-this-might-help/]
+== list available services ==
-==list available services==
   systemctl list-unit-files
 or
   systemctl list-units
+&nbsp;
+== normal interface names ==
-==normal interface names==
   net.ifnames=0
+== Show failed services ==
+ systemctl --failed
+&nbsp;
+== systemd: Started Session ==
+Change loglevel to notice in /etc/systemd/system.conf
+ systemctl daemon-reexec
+==Status==
+=== Active: inactive (dead) ===
+parameter ActiveState would return inactive
+SubState returns dead

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