The system journal, systemd-journald

As of 2015, systemd replaced SysV Init as a de facto system and service manager in most major Linux distributions. As a consequence, the journal daemon  journald has become the standard logging component, superseding syslog in most aspects. Thus, the journalctl utility is necessary to read the logs.

Control the systemd login manager

journalctl is used to read and query systemd's journal database.
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However, if invoked with the -k or --dmesg switches, it will be equivalent to using the dmesg command:
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other interesting journalctl options are:

  • -b shows boot information.
  • -u shows messages about a specified unit.
  • -f shows most recent journal messages and keeps printing new entries as they are appended to the journal.