MAN: manual refers to the manual. You can use this command to query the usage of other commands.
PWD: Print working directory indicates a password.
Su: Switch the swith user to the root user.
CD: Change directory switch directory
Ls: List Files
PS: Process status
Mkdir: Make directory to create a directory
Rmdir: Remove directory move directory
Mkfs: Make File System: create a file system
Fsck: File System check file system check
Cat: concatenate
Uname: Unix name system name
DF: disk free hard disk
Du: disk usage hard disk usage
Lsmod: List modules list Module
MV: Move file move file
RM: Remove File delete file
CP: copy file
LN: link files
FG: foreground
BG: Background
Chown: change owner
Chgrp: Change Group Change User Group
Chmod: Change Mode change mode
Umount: unmount uninstall
DD: "convert an copy" should have been named "cc" according to its function description, but "cc" has been used to represent "C Complier", so it is named "DD"
Tar: tape archive decompress the file
LDD: list dynamic dependencies list dynamic Dependencies
Insmod: Install module installation Module
Rmmod: Remove module Delete Module
Lsmod: List module list Module