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htop - Process Management

install htop

Every system administrator likes to use some of the more commonly used commands. Today I recommend htop as an alternative to the top command. To use the htop command usually, you need to install it first.

# Installation epel source (also called repository)
dnf -y install epel-release
# Generate cache
dnf makecache
# Install htop
dnf -y install htop

Use htop

You only need to type htop in the terminal, and the interactive interface is as follows:

0[ |||                      3%]     Tasks: 22, 46thr, 174 kthr 1 running
1[ |                        1%]     Load average: 0.00 0.00 0.05
Mem[ |||||||           197M/8G]     Uptime: 00:31:39
Swap[                  0K/500M]
PID   USER   PRI   NI   VIRT   RES   SHR   S   CPU%   MEM%   TIME+   Command(merged)
...

F1 Help F2 Setup F3 Search F4 Filter F5 Tree F6 SortBy F7 Nice F8 Nice F9 Kill F10 Quit

Top Description

  • The top 0 and 1 indicate the number of your CPU cores, and the percentage indicates the occupancy rate of a single core (of course, the total occupancy rate of the CPU can also be displayed)

    • The different colors of the progress bar indicate the percentage of different process types:

      Color Description Names displayed in other styles
      Blue Percentage of CPU used by low-priority processes low
      Green Percentage of process CPU owned by ordinary users
      Red Percentage of CPU used by system processes sys
      Cyan Percentage of CPU consumed by Steal Time vir

  • Tasks: 22, 46thr, 174 kthr 1 running. In my example, it means that my current machine has 22 tasks, which are divided into 46 threads, of which only 1 process is in a running state, "kthr" indicates how many kernel threads there are.

  • Mem information. Similarly, use different colors to distinguish:
Color Description Names displayed in other styles
Blue Percentage of memory consumed by the buffer buffers
Green Percentage of memory consumed by the memory area used
Yellow/Orange Percentage of memory consumed by the cache area cache
Magenta Percentage of memory occupied by shared memory area shared
  • Swap information.
Color Description Names displayed in other styles
Green Percentage of swap consumed by the swap area used
Yellow/Orange Percentage of swap consumed by the cache area cache
  • Load average, the three values ​​respectively represent the average load of the system in the last 1 minute, the last 5 minutes, and the last 15 minutes
  • Uptime, which means the running time after booting

Process information description

  • PID - Process ID number
  • USER - The owner of the process
  • PRI - Displays the process priority as seen by the Linux kernel
  • NI - Displays the process priority of reset by normal user or root super user
  • VIRT - Virtual memory being consumed by a process
  • RES - Physical memory being consumed by a process
  • SHR - Shared memory being consumed by a process
  • S - The current state of the process, there is a special state to pay attention to! That is Z (zombie process). When there are a large number of zombie processes in the machine, it will affect the performance of the machine.
  • CPU% - Percentage of CPU consumed by each process
  • MEM% - Percentage of memory consumed by each process
  • TIME+ - Shows the running time since the process was started
  • Command - The command corresponding to the process

Shortcut key description

In the interactive interface, press the F1 button to see the corresponding shortcut key description.

  • The up, down, left, and right direction keys can scroll through the interactive interface, and Space can mark the corresponding process, which is marked in yellow.
  • The N button, the P button, the M button and the T button are respectively PID, CPU%, MEM%, TIME+ is used for sorting. Of course, you can also use the mouse to click to sort in ascending or descending order of a certain field.

Other commonly used

To manage the process, use the F9 button to send different signals to the process. The list of signals can be found in kill -l. The more commonly used ones are:

Signal Description
1 Lets the process shut down immediately, and then restart after re-reading the configuration file
9 Used to immediately end the running of the program, used to forcibly terminate the process, similar to the forced end in the windows taskbar
15 The default signal for the kill command. Sometimes if a problem has occurred in the process and the process cannot be terminated normally with this signal, we will try signal 9

End

htop is much easier to use than the top that comes with the system, it is more intuitive, and it improves daily use greatly. This is why htop is usually one of the first packages the author installs after installing a new operating system.

Author: tianci li

Contributors: Steven Spencer