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Linux Administration/System Services/System Logging/Journalctl

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Journalctl command allows to query the contents of the systemd journal/logs.

Configuration

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  • /etc/systemd/journald.conf

Basic Commands

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  • journalctl[1] or journalctl --no-pager
  • journalctl -r (reverse order)
  • journalctl -k : Show only kernel messages
  • journalctl -f (follow)
  • journalctl -u service-name.service
journalctl -u libvirtd
  • journalctl --verify
  • Disk Usage/Logging: journalctl --disk-usage
  • journalctl --vacuum-size=200M[2]
    • --vacuum-size=BYTES Reduce disk usage below specified size
    • --vacuum-files=INT Leave only the specified number of journal files
    • --vacuum-time=TIME Remove journal files older than specified time
  • journalctl --list-boots. See also: last (command)

See also

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  • systemd and related daemons: systemd, systemd-journald, systemd-logind, systemd-networkd (networkctl), systemd-timesyncd, systemd-resolved and systemd-udevd[3]
  • /etc/inittab[4] and respawn option[5]
  • systemctl
  • launchd init and operating system service management daemon for MacOS
  1. ↑ https://www.freedesktop.org/software/systemd/man/journalctl.html
  2. ↑ https://askubuntu.com/a/1012913
  3. ↑ https://wiki.ubuntu.com/DebuggingSystemd
  4. ↑ https://linux.die.net/man/5/inittab
  5. ↑ https://superuser.com/questions/507576/how-to-automatically-restart-a-linux-background-process-if-it-fails
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