Systemd is an init system used in many Linux distributions such as CentOS, Ubuntu, Debian and others to bootstrap the user space and manage all processes subsequently. The systemd journal is nothing but a system service that collects and stores logging data.
From the blog:
It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources: Not everything integrates with the systemd journal. Here is how you can force-feed log files from programs that don’t work with systemd into the journal.
Lets assume you want to import the /var/log/awesome.log written by the awesomed example service process to the journal. awesomed, like most services, is managed by the systemd init system and such has a service unit file.
- Read more: Feeding log files to the systemd journal