For web server administrators such as myself, error messages like Job for foo.service failed because the control process exited with error code can often be difficult to decipher and troubleshoot. Fortunately, the Linux utility dmesg can be a powerful tool for determining the root cause of the issue and determining the necessary steps for resolution.
What is the dmesg Command?
For those who may be unfamiliar with the dmesg command, it is a Linux utility that allows an administrator to view as well as control the kernel message buffer. This message buffer is used to store the output from the kernel as it is booting, as well as all kernel-related messages generated during system runtime.
Using dmesg to Troubleshoot Error Messages
In this case, dmesg can be used to troubleshoot the issue with Job for foo.service failed because the control process exited with error code. To begin, log onto the system in question as a user with superuser or root privileges and enter the command dmesg. Any kernel messages related to foo.service should appear near the end of the output. For instance, if a lack of permissions or dependencies is causing the error, it can easily be identified with dmesg.
If the cause of the error is not immediately identifiable, additional runtime information can be obtained by running dmesg with the -x option. For more detailed information about the process, look for errors associated with foo.service and the /var/log/syslog for disturbingly relevant messages with timestamps.
Determining the Necessary Resolution Steps
After locating the messages related to foo.service, it should be a simple matter of determining the necessary resolution steps. For instance, if the error was caused by an invalid configuration, you would simply need to update or reconfigure the related .service file. On the other hand, if the problem is caused by a dependency, it may be necessary to install the necessary dependencies in order to run the service.
In conclusion, the Linux utility dmesg can be a powerful tool for troubleshooting error messages, such as Job for foo.service failed because the control process exited with error code. By running the command with the -x option, an administrator can easily locate additional runtime messages and determine the necessary steps for resolution.
