错误：Failed to start squid.service: Unit squid.service is masked

You can try the following steps to resolve the "Failed to start squid.service: Unit squid.service is masked" error:

1. Open Terminal and enter the following command to check the status of the Squid service:

systemctl status squid.service

2. If the result shows `masked`, it means that the service has been disabled. You need to execute the following command to unmask it:

sudo systemctl unmask squid.service

3. After unmasking, you can use the following command to start the Squid service:

sudo systemctl start squid.service

4. To enable the Squid service to start automatically, type the following command (optional):

sudo systemctl enable squid.service

These steps should help you resolve "Failed to start squid.service: Unit squid.service is masked" error and enable Squid service.

If you encounter an error again:

Job for squid.service failed because the service did not take the steps required by its unit configuration. See "systemctl status squid.service" and "journalctl -xeu squid.service" for details.

This error means that the Squid service did not follow the steps required by its configuration file. You can fix it by following these steps:

1. Open a terminal and enter the following command to view the status of the Squid service:

sudo systemctl status squid.service

2. If the service is stopped, run the following command to start the Squid service:

sudo systemctl start squid.service

3. If the service still fails to start, run the command in the first step again to view more information. This will issue the following prompt: The "journalctl -xe" command can display more detailed error messages.

4. Run the following command to view more log information about the Squid service:

sudo journalctl -xeu squid.service

5. According to the error message provided in the log information, try to solve the problem that the Squid service cannot be started.

6. If you cannot solve the problem, you can try to restart the Squid service, run the following command:

sudo systemctl restart squid.service

The above steps should help resolve the Squid service failed to start errors displayed by the "systemctl status squid.service" and "journalctl -xeu squid.service" commands.