Logging in Linux

In earlier chapters, we already encountered the journalctl command. In this chapter, I'll discuss this command in much more detail.

In Linux distributions, such as the latest versions of RHEL/CentOS, Debian, Ubuntu and SUSE, that uses systemd as their init system, the systemd-journald daemon is used for logging. This daemon collects the standard output of a unit, syslog message, and, if the application support it: direct messages from the application to systemd.

The logs are collected in a database that can be queried with journalctl.

Working with journalctl

If you execute systemctl status <unit>, you already see the last entries of the logging. To see the full log, journalctl is the tool that you...