How do I make journalctl messages show up in red?

Question

Some error messages in journalctl show up in red and white. If I'm authoring my own systemd service, how can I format my messages such that they show up in red or white. It's a nice way of having errors stand out.

Answer 1

It's the priority that determines how journalctl displays messages.

Based on a quick test with logger :

• Messages of priority debug and info are displayed "normally".
• Messages of priority notice and warning are displayed in bold white.
• Messages of priority err, crit, alert, emerg are displayed in bold red.

Edit:

To answer the comment about how to indicate a level just by writing to stdout, yes you can, just prefix your message with <n> where n is a number between 0 (emerg) and 7 (debug) representing the priority.

For example the following service writes an alert message, which will thus appear in red in journalctl output :

[Unit]
Description=Loth

[Service]
ExecStart=/bin/echo "<1>Victoriae mundis et mundis lacrima."

[Install]
WantedBy=multi-user.target

See sd-daemon(3) and http://0pointer.de/blog/projects/journal-submit.html for more details.