Troubleshoot Zombie/Defunct Processes in UC Servers

When a process terminates, it enters the defunct state for a long period. This state enables the parent process to monitor the exit status of the processes that are currently running. The kernel will not remove kernel structures associated with the process table until the parent has either examined the exit state of the child process or informed the kernel. If the parent process terminates without performing one of these actions, the system will never remove the child’s structures, and the child process will remain a dead process.

Troubleshoot/Clear the Zombies Manually

Zombie processes do not consume any system resources, except the small amount of memory necessary to store the PID, which was previously indicated. However, they do preserve their process ID. UC servers have vast amounts of memory available to them, which means that it is unlikely that the system will run out of PIDs for other processes due to the presence of Zombies on the system. Consequently, the zombies can be left on the Cisco Router, where they will be automatically deleted when the system is rebooted the following time.

The parent process is responsible for deleting zombies from the process table. When a parent exits without deleting its zombies, the operating system will try and remove them. Machine administrators may usually remove zombies from the process control block by rebooting the system. Here is the exception. Because a zombie has stopped running, putting the kill command on it has no impact. It may still need to read exit information and updates to work properly.

What is a Defunct Process?

A process can stop executing but remain in the process table for the parent to collect exit information and updates before deleting the process from the process table. Because it is no longer in operation, it just requires RAM to keep the exit status and other process-relevant information in the place where it shows in the process table, and it does not require any additional RAM.

It is crucial to understand that when a process comes to an end, it is considered a defunct process. In most cases, defunct processes are terminated by the parent process almost quickly after they are created. Thus they do not appear in the ps output. In extremely unusual conditions, zombies can be observed in the output of the ps command for extended periods. Zombies are an inherent element of every Unix operating system, but having an excessive number of them in the process table might cause problems.

Conclusion

Additionally, a defunct process is referred to as a zombie process or an orphaned process. Certain resources, such as memory, may remain connected with a deceased process and are unavailable for usage. A stopped process cannot be terminated. Apart from the minuscule RAM necessary to store the PID, Zombies Attack process consume no system resources yet keep their process ID. Owing to the enormous amount of RAM allocated to UC servers, the likelihood of the system running out of PIDs for other processes owing to the combination of Zombies is quite unlikely.