Journald

Journal is part of systemd. Messages from various parts of a systemd-enabled Linux machine are collected here. This comprises notifications from the kernel and boot process, syslog, and other services.

Traditionally, during Linux’s boot process, the OS’s many subsystems and application daemons would each log messages in text files. Different levels of detail would be logged for each subsystem’s messages. When troubleshooting, administrators often had to sift through messages from several files spanning different periods and then correlate the contents. The journaling feature eliminates this problem by centrally logging all system and application-level messages.

The systemd-journald daemon is in charge of the journal. It gathers data from several resources and inserts the gathered messages into the diary.

When systemd is using in-memory journaling, the journal files are generated under the /run/log/journal folder. If there isn’t already...