If you use systemd units or systemd-run to conveniently capture output from scripts and programs into the systemd journal, one of the things that it looks like you don't get is message priorities and (syslog) facilities. Fortunately, systemd's journal support is a bit more sophisticated than that.

When you print out regular output and systemd captures it into the journal, systemd assigns it a default priority that's set with SyslogLevel= ; this is normally 'info', which is a good default choice. Similarly, you can pick the syslog facility associated with your unit or your systemd-run invocation with SyslogFacility= . Systemd defaults to 'daemon', which may not entirely be what you want. On the other hand, the choice of syslog facility matters less if you're primarily working with journalctl , where what you usually care about is the systemd unit name.

(You can use journalctl to select messages by priority or syslog facility with the -p and --facility options. You can also select by syslog identifier with the -t option. This is probably going to be handy for searching the journal for messages from some of our programs that use syslog to report things.)

If you know that you're logging to systemd (or you don't care that your regular output looks a bit weird in spots), you can also print messages with special priority markers, as covered in sd-daemon(3) . Now that I know about this, I may put it to use in some of our scripts and programs. Sadly, unlike the normal Linux logger and its --prio-prefix option, you can't change the syslog facility this way, but if you're doing pure journald logging you probably don't care about that.

(It's possible that sd-daemon(3) actually supports the logger behavior of changing the syslog facility too, but if so it's not documented and you shouldn't count on it. Instead you should assume that you have to control the syslog facility through setting SyslogFacility= , which unfortunately means you can't log just authentication things to 'auth' and everything else to 'daemon' or some other appropriate facility.)

PS: Unfortunately, as far as I know journalctl has no way to augment its normal syslog-like output with some additional fields, such as the priority or the syslog facility. Instead you have to go all the way to a verbose dump of information in one of the supported formats for field selection .