Systemd
From DWIKI
Documentation
- Useful systemd commands
- http://www.freedesktop.org/wiki/Software/systemd/
- https://wiki.ubuntu.com/systemd
- Creating systemd service
- https://wiki.ubuntu.com/SystemdForUpstartUsers
- How To Use Systemctl to Manage Systemd Services and Units
- How to switch from NetworkManager to systemd-networkd on Linux
- https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet
- Predictable Network Interface Names
- [https://blog.darknedgy.net/technology/2020/05/02/0/index.html#tech-critique
- Systemd service tutorial
- https://www.freedesktop.org/wiki/Software/systemd/dbus/ Systemd and dbus
- Single user/emergency
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
Without editing netplan
resolvectl dns eth0 8.8.8.8 8.8.4.4
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
now use
resolvectl flush-caches
All status
systemctl status -a
syslog spam
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
