My favorite Linux top command options

When I check a Linux system (or even troubleshoot a computer running another operating system), I often use the top command to check the system's RAM and CPU usage. It provides me with information to assess the overall health of my computer. I learned about the top command early in my Linux journey and relied on it to give me a quick overview of what was going on on a server or other Linux system, including a Raspberry Pi. But there's more to the top command than meets the eye. According to its man page, the top program provides a dynamic, real-time view of a running system. It displays system summary information and a list of processes or threads currently managed by the Linux kernel.

However, there is more to the top command than meets the eye. The specific functionality of your top command may vary depending on the version you are running (procps-ng, Busybox, BSD), so see the man page for details.

To start top, enter in the terminal:

linuxmi@linuxmi:~/www.linuxmi.com$ top

Running processes are displayed below the table title on the top screen, and system statistics are displayed above it.

top - 09:46:05 up  1:33,  1 user,  load average: 0.76, 0.67, 0.74
任务: 350 total,   1 running, 349 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.0 us,  0.7 sy,  0.0 ni, 97.8 id,  0.0 wa,  0.0 hi,  0.5 si,  0.
MiB Mem :   3886.8 total,    307.9 free,   2175.1 used,   1403.8 buff/cache
MiB Swap:   2048.0 total,    435.8 free,   1612.2 used.   1332.7 avail Mem 

 进程号 USER      PR  NI    VIRT    RES    SHR    %CPU  %MEM     TIME+ 
   5816 mssql     20   0 9489420 315860  26100 S   2.3   7.9   2:12.97 
     99 root       0 -20       0      0      0 I   0.7   0.0   0:09.20 
   1141 root      20   0  242936   6504   5452 S   0.7   0.2   0:37.47 
  11835 linuxmi   20   0 4041480 290588  75920 S   0.7   7.3   2:16.77 
   1924 root      20   0   66412   4732   4156 S   0.3   0.1   0:14.17 
   2815 vcache    20   0  278864  87112  85116 S   0.3   2.2   0:03.56 
   3371 linuxmi+  20   0  190672   5148   3132 S   0.3   0.1   0:04.49 
   3598 linuxmi+  20   0   57108   2404   2032 S   0.3   0.1   0:16.62 
   5864 tr_test   20   0  190672   5780   3080 S   0.3   0.1   0:04.62 

Press the Z key to change the color of the output. I find this makes the output easier on the eye.

Press the 1 key to view a graphical representation of each CPU core on the system. Press 1 repeatedly to evaluate the kernel statistics of the CPU core.

You can graphically display memory usage by calling the top command and then pressing the m key.

Useful top options

If you are only looking for processes started by a specific user, you can use the following -u option to get that information:

linuxmi@linuxmi:~/www.linuxmi.com$ top -u 'root'

To obtain a list of idle processes on the system, use the following -i option:

linuxmi@linuxmi:~/www.linuxmi.com$ top -i

You can set the update interval to any value in seconds. The default value is 3 seconds. Change it to 5 like this:

linuxmi@linuxmi:~/www.linuxmi.com$ top -d 5

You can also run top on a timer. For example, the following command sets the number of iterations to two and then exits:

linuxmi@linuxmi:~/www.linuxmi.com$ top -n 2

Use top to locate a process

Press Shift L to find processes by name. This creates a hint above the bold table title row. Enter the name of the process you want to find and press Enter or Return to see instances of that process highlighted in the newly sorted list of processes.

Use top to stop the process

You can also use top to stop or "kill" a running process. First, find the process you want to stop using Shift L or pgrep. Next, press K and enter the ID of the process you want to stop. The default value is whatever is at the top of the list, so make sure you enter the PID you want to stop before pressing Enter, otherwise you might stop a process you didn't intend to stop.

top iteration

This command has many iterations top, including htop, atop, btop and ttop. There are also specialized top commands, such as the Linux power saving tool powertop and the network traffic monitoring tool ntop.

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