Linux system information and running status monitoring

by Nam Phong · February 24, 2020

In the file system of Linux, there is a special directory “/proc”. Many interesting things can be found in this directory, such as

/proc/cpuinfo //Information about the local CPU
/proc/meminfo //Usage information of local memory and swap partition
/proc/modules// Information about the hardware modules installed on the machine
/proc/mounts //Device information on the mounted mount

In addition, there are a number of subdirectories under this directory. Each subdirectory is used to maintain a running process, and the directory name is the corresponding process ID.

For example, enter the subdirectory named “1”:

cd /proc/1

The content in the file “cmdline” in this directory is the command line executed when the process is running; the content in the “environ” file is the environment variable information when the process is running; the status of the process when it is stored in the “stat” file Information, etc.

By looking at the files in the “/proc” directory, you can obtain almost all system information and system operating status information. In fact, many commands for querying system status information under Linux are also obtained by reading files in this directory.

Here are some commands for viewing system status information:

df command

Used to view the status information of the Linux file system, and display the capacity, used, unused, and mount points of each partition. Such as:

- df -k //Display information for each partition in kilobytes (KB)
- df -a //Display all partitions, including partitions of size 0
- df -T //Displays the partition type (EXT2 or EXT3, etc.)

du command

Lets you view the size of a file or folder. Such as:
du -b /home //Show the size of each subfolder under the “/ home” folder in bytes
du -ks home //Display the total size of the “/home” folder in kilobytes (KB)

top command

Used to view system status information in real-time. After running this command, the following information will be displayed on the screen:

- CPU states: including user process occupancy rate, system process occupancy rate, user priority process occupancy rate, and idle CPU resource rate
- Memory status (Mem): including total memory, usage, free capacity, etc
- Swap status: Includes the total amount of swap partitions, usage, and free capacity
- Status of each process: including process ID, user name, priority, CPU and memory usage, and the command line executed when the process was run

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