### Understand the alert

The `systemd_target_unit_failed_state` alert is triggered when a `systemd` target unit goes into a failed state. Systemd is the system and service manager for Linux, and target units are groups of systemd units that are organized for a specific purpose. If this alert is triggered, it means there is an issue with one of your systemd target units.

### What does failed state mean?

A systemd target unit in the failed state means that one or more units/tasks of that target, whether it's a service, or any other kind of systemd unit, have encountered an issue and cannot continue running.

### Troubleshoot the alert

1. First, you need to identify which systemd target unit is causing the alert. You can list all the failed units by running:

   ```
   systemctl --failed --all
   ```

2. Once you have identified the problematic target unit, check its status for more information about the issue. Replace `<target_unit>` with the actual target unit name:

   ```
   systemctl status <target_unit>
   ```

3. Look at the logs of the failed target unit to collect more details on the issue:

   ```
   journalctl -u <target_unit>
   ```

4. Based on the information gathered in steps 2 and 3, troubleshoot and fix the problem(s) in your target unit. This may involve:
   - Editing the unit file
   - Checking the services and processes that compose the target
   - Looking into configuration files and directories.

5. Reload the systemctl daemon to apply any changes you made, then restart the target unit:

   ```
   sudo systemctl daemon-reload
   sudo systemctl restart <target_unit>
   ```

6. Verify that the target unit has been successfully restarted:

   ```
   systemctl is-active <target_unit>
   ```

7. Continue monitoring the target unit to ensure that it remains stable and does not return to a failed state.

### Useful resources

1. [systemd man pages (targets)](https://www.freedesktop.org/software/systemd/man/systemd.target.html)
2. [systemd Targets - ArchWiki](https://wiki.archlinux.org/title/Systemd#Targets)