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Systemd

References

https://www.freedesktop.org/software/systemd/man/systemctl.html
https://access.redhat.com/attachments/12052018_systemd_6.pdf

• Manage services and units

  https://www.digitalocean.com/community/tutorials/

  sudo systemctl status application.service

  sudo systemctl start application.service
  sudo systemctl stop application.service
  

  sudo systemctl enable application.service
  sudo systemctl disable application.service
  

  sudo systemctl restart application.service
  sudo systemctl reload application.service
  

  sudo systemctl daemon-reload

• Modify unit file

  https://serverfault.com/questions/840996/

  systemctl edit <service-name>

• List services

  https://askubuntu.com/questions/795226/

  systemctl list-unit-files --type=service
  systemctl list-unit-files | grep "enabled "
  systemctl --no-pager list-units
  systemctl | grep running
  

• List timers

  systemctl --no-pager list-timers

Log files

https://www.golinuxcloud.com/view-logs-using-journalctl-filt

• journalctl

  last 100 lines : journalctl -b -f --lines=100

  last errors : journalctl --no-pager -b -p 4

  last errors : journalctl --no-pager -b -p err

• Read shutdown log

  journalctl -b -1 -e

• Using logrotate

  https://journaldunadminlinux.fr/rotation-des-logs-avec-logro

• Delete old files

  https://unix.stackexchange.com/questions/139513/

  delete older than 2 days : sudo journalctl --vacuum-time=2d

  check result : sudo du /var/log -x | sort -nr | head -10

Turn off excessive logs

• rtkit-daemon

  https://unix.stackexchange.com/questions/684379/

  sudo mkdir /etc/systemd/system/rtkit-daemon.service.d/
  sudo nano /etc/systemd/system/rtkit-daemon.service.d/log.conf
  

  Add the following :

  [Service]
  LogLevelMax=4
  

  Reload the service

  sudo systemctl daemon-reload
  sudo systemctl restart rtkit-daemon.service
  

• sudo

  https://unix.stackexchange.com/questions/224370/
  https://unix.stackexchange.com/questions/637227/

  sudo nano /etc/pam.d/sudo

  add the following with the corresponding user name :

  session [success=1 default=ignore] pam_succeed_if.so quiet uid = 0 ruser = <username>

  Example of /etc/pam.d/sudo file :

  #%PAM-1.0
  
  # Set up user limits from /etc/security/limits.conf.
  session    required   pam_limits.so
  session [success=1 default=ignore] pam_succeed_if.so quiet uid = 0 ruser = hotnuma
  
  @include common-auth
  @include common-account
  @include common-session-noninteractive
  

Other

• Analyze startup

  systemd-analyze
  systemd-analyze --no-pager blame
  systemd-analyze critical-chain
  

• Disable gvfs-backends

  using bak from systools : https://github.com/hotnuma/systools

  sudo bak /usr/share/gvfs/remote-volume-monitors/afc.monitor
  sudo bak /usr/share/gvfs/remote-volume-monitors/goa.monitor
  sudo bak /usr/share/gvfs/remote-volume-monitors/gphoto2.monitor
  sudo bak /usr/share/gvfs/remote-volume-monitors/mtp.monitor