CompTIA Linux+ XK0-005 - 4.3 - Runaway Processes

In Linux environments, runaway processes can cause high CPU utilization and memory consumption, leading to system slowdowns or unresponsiveness. It is crucial to identify and terminate these runaway processes to restore system stability and optimize resource utilization. This guide will provide you with the necessary steps to identify and terminate runaway processes effectively.

Identifying Runaway Processes with top

One way to identify runaway processes is by using the top command, which provides a real-time overview of system resource usage and running processes. You can sort the processes based on their resource usage to identify those consuming a significant amount of CPU resources.

top

The top command displays a list of running processes, their resource usage, and other system metrics.

Example

top - 12:00:00 up 1 day,  1:30,  1 user,  load average: 0.85, 0.78, 0.92
Tasks: 249 total,   2 running, 247 sleeping,   0 stopped,   0 zombie
%Cpu(s): 10.2 us,  5.0 sy,  0.0 ni, 84.8 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   7822.4 total,    207.4 free,   6817.6 used,    797.4 buff/cache
MiB Swap:   2048.0 total,   1451.9 free,    596.1 used.    787.7 avail Mem 
   PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
  1858 john      20   0 2334760 344440  44712 R  99.5   4.3   0:29.78 chromium
  1832 john      20   0  806156 131252  47584 S   5.8   1.6   0:21.52 gnome-shell
...

The output displays a list of running processes, including their process IDs (PIDs), CPU utilization (%CPU), memory usage (%MEM), and other details.

Observe the %CPU column to identify processes with high CPU utilization. Runaway processes often have a significantly higher CPU usage than other processes.

In the above example, the process with PID 1858 (chromium) has a high CPU usage of 99.5%.

Identifying Runaway Processes with ps

Another command that can help identify runaway processes is ps. The ps command provides detailed information about running processes on a Linux system.

To identify runaway processes using ps, run:

ps aux --sort=-%cpu

The ps aux command displays all running processes and their details, while the --sort=-%cpu option sorts the processes based on CPU usage in descending order.

Example

USER       PID %CPU %MEM     VSZ    RSS TTY STAT START    TIME COMMAND
john      1858 99.5  4.3 2334760 344440 ?     Rl 12:00 0:29.78 chromium
root       671  2.2  0.0       0      0 ?      S May15  100:51 [kworker/2:0]
john      1832  1.0  1.6  806156 131252 ?    Ssl May15 0:21.52 gnome-shell
...

The output provides information about each process, including the user, PID, CPU usage (%CPU), memory usage (%MEM), and the command being executed.

Look for processes with high CPU usage (%CPU) as they may indicate runaway processes.

In the above example, the process with PID 1858 (chromium) has a high CPU usage of 99.5%.

Terminating Runaway Processes

Once you have identified a runaway process, you can terminate it to alleviate CPU and memory resource constraints. The kill command is used to send a termination signal to a process.

To terminate a runaway process, follow these steps:

Identify the PID of the runaway process using either the top or ps command.
Open a terminal and run the following command, replacing <PID> with the actual PID of the runaway process:
```
kill <PID>
```
The kill command sends a termination signal (SIGTERM) to the specified process, instructing it to exit gracefully.
Example
```
kill 1858
```
After executing the command, the runaway process should receive the termination signal and exit shortly.

Tip

you may have to run kill -9 <pid> to force the process to terminate but this should be used as a last resort.
After terminating the runaway process, monitor the system resources again to ensure that the CPU and memory usage return to normal levels.

Conclusion

In this guide, we explored the topic of analyzing and troubleshooting CPU and memory issues caused by runaway processes in Linux environments. We defined runaway processes as those that consume excessive system resources and degrade system performance. We discussed the steps involved in identifying runaway processes using the top and ps commands and terminating them using the kill command.

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