Linux Beast

TOP Command Output Fields

The top command in Linux displays the running processes on the system. One of the most important tools for a system administrator. It is used extensively for monitoring the load on a server. In this article, we explore the top command in detail. The top command is an interactive command.

1.1 Uptime and Load Averages:

At the top of top command is displayed the output similar to uptime command.

The fields display:

* current time

* the time your system is been up

* number of users logged in

* load average of 5, 10 and 15 minutes respectively.

This uptime display can be toggled with ‘l’ command.

1.2 Tasks:

The second line shows summary of tasks or processes. The processes can be in different states. It shows total number of the processes. Out of these, the processes can be running, sleeping, stopped or in zombie (zombie is the state of a process state, These process summary can be toggled with ‘t’ command.

1.3 CPU States:

Next is shown the CPU state. Here, %age of CPU time in different modes is shown. The meaning of different CPU times are:

* us, user: CPU time in running (un-niced) user processes

* sy, system: CPU time in running kernel processes

* ni, niced: CPU time in running niced user processes

* wa, IO wait: CPU time waiting for IO completion

* hi: CPU time serving hardware interrupts

* si: CPU time serving software interrupts

* st: CPU time stolen for this vm by the hipervisor.

1.4 Memory Usage:

Next two lines show memory usage, somewhat like ‘free’ command. 1st of these lines is for physical memory and the second for virtual memory (swap space).

The physical memory is displayed as: total available memory, used memory, free memory, and memory used for buffers

Similarly, swap reflects: total, used, free and cached swap space.

The memory can be toggled with ‘m’ command.