# Analyzing systemd Logs with journalctl
The `journalctl` tool queries the contents of the `systemd` journal.
The following command displays the messages that `systemd` generated the last time the machine started:
journalctl -b
The following command reveals the messages for the systemd service unit specified by the `-u` option:
journalctl -u auditd
In the above example, `auditd` is the system service unit.
For more information, see the `journalctl` man page by running the following command on Photon OS:
```
man journalctl
```