thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Systems & Data Center · Intermediate

journalctl

The command for querying logs collected by systemd-journald, filtered by unit, time, priority or boot.

Definition

journald stores structured binary logs; journalctl -u unit filters by service, -b by boot, -p err by priority, -f follows live and --since filters by time. Persistent storage requires /var/log/journal or Storage=persistent in journald.conf.

Example

journalctl -u nginx --since '1 hour ago' -p warning shows recent warnings for nginx.

Exam tip

By default on some distributions the journal is volatile; create /var/log/journal to keep logs across reboots.

Related terms