Other letters to watch for are l which means the process is multi-threaded and R which means the processes is running. STAT is the status of the process, where S means the process is sleeping and can be woken at any time, N means the process has a low priority, and < means the process has a high priority. RSS is similar to VSZ, but rather than virtual memory size, RSS shows how much non-swapped, physical memory the process is using in kilobytes. VSZ show the virtual memory size of the process in kilobytes. %MEM is the amount of the physical memory the process is using. It is the CPU time used divided by the time the process has been running expressed as a percentage. %CPU shows the CPU utilization of the process. USER is the name of the user that owns the processes.Įach process has a unique process ID (or PID for short). Here is a brief explanation of each of the columns: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND

Here are the first few lines from my CentOS 5 test machine:

ps has many options, but one of the most useful invocations is ps aux, which shows every process on the system.Ī normal Linux server may have 100 processes running after boot up, so the output from the ps command can be quite long.

Ps shows the current processes running on the machine. To help, turn to command-line tools such as ps, top, service, kill, and killall. Knowing how to manage rogue processes is an essential part of Linux system management. If a program goes wrong, it can start to use too much CPU time or memory and so deny other programs the resources they need to run. What do you do if one of your services stops working? Here are some handy command-line tools for managing processes.Įach process uses time on a system’s CPU, as well as other system resources such as memory and disk space. Each of these programs runs as a separate process. For example, a typical Linux server might include a Web server, an email server, and probably a database service. All modern operating systems are able to run many programs at the same time.

Process monitor operating system