### Understand the alert

The `systemd_socket_unit_failed_state` alert is triggered when a `systemd` socket unit on your Linux server enters a failed state. This could indicate issues with the services that depend on these socket units, impacting their functionality or performance.

### What is a systemd socket unit?

`systemd` is the system and service manager for modern Linux systems. It initializes and manages the services on the system, ensuring a smooth boot process and operation.

A socket unit is a special kind of `systemd` unit that encapsulates local and remote IPC (Inter-process communication) sockets. They are defined by .socket files and are used to start and manage services automatically when incoming traffic is received on socket addresses managed by the socket unit.

### Troubleshoot the alert

1. Identify the failed socket unit(s):

To list all the socket units with their current state, run:

```
systemctl --state=failed --type=socket
```

This command will display the socket units in a failed state.

2. Check the status of the failed socket unit:

To view the detailed status of a particular failed socket unit, use:

```
systemctl status your_socket_unit.socket
```

Replace `your_socket_unit` with the name of the failed socket unit you're investigating. This will provide more information about the socket unit and possible error messages.

3. Examine the logs:

Check the logs for any errors or issues related to the failed socket unit:

```
journalctl -u your_socket_unit.socket
```

Replace `your_socket_unit` with the name of the failed socket unit you're investigating. This will display relevant logs for the socket unit.

4. Restart the failed socket unit:

Once the issue is identified and resolved, you can attempt to restart the failed socket unit:

```
systemctl restart your_socket_unit.socket
```

Replace `your_socket_unit` with the name of the failed socket unit you're investigating. This will attempt to restart the socket unit and put it into an active state.

5. Monitor the socket unit:

After restarting the socket unit, monitor its status to ensure it stays active and operational:

```
systemctl status your_socket_unit.socket
```

Replace `your_socket_unit` with the name of the failed socket unit you're investigating. Verify that the socket unit remains in an active state.

### Useful resources

1. [Sockets in Systemd Linux Operating System](https://www.freedesktop.org/software/systemd/man/systemd.socket.html)
