To list all failed units (services) in a systemd-based Linux system, you can use the systemctl command with the --failed option.
For example:
systemctl --failed
This will show a list of all units (services) that have failed to start or that are in a failed state. The list will include the unit names, unit descriptions, and the current state of each unit.
You can also use the --all option to list all units, including inactive units:
systemctl --all --failed
This will show a list of all units, including units that are not currently enabled or active.
Note: These commands assume that you have root access to your system. You will need to use sudo to run them.
You can use the systemctl status command to get more detailed information about a specific unit. For example:
systemctl status unitname
This will show the current status of the unit, as well as any error messages or log output that may be relevant to troubleshooting the issue.
By using these commands, you can identify and troubleshoot any failed units (services) on your Linux system.