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The chmod command

The chmod command allows you to change the permissions on a file using either a symbolic or numeric mode or a reference file.

Examples:

1. Change the permission of a file using symbolic mode:

chmod u=rwx,g=rx,o=r myfile

The command above means :

• user can read, write, execute myfile
• group can read, execute myfile
• other can read myfile

2. Change the permission of a file using numeric mode

chmod 754 myfile user:group file.txt

The command above means :

• user can read, write, execute myfile
• group can read, execute myfile
• other can read myfile

3. Change the permission of a folder recursively

chmod -R 754 folder

Syntax:

chmod [OPTIONS] MODE FILE(s)

• [OPTIONS] : -R: recursive, mean all file inside directory

• MODE: different way to set permissions:

• Symbolic mode explained

  • u: user
  • g: group
  • o: other
  • =: set the permission
  • r: read
  • w: write
  • x: execute
  • example u=rwx means user can read write and execute

• Numeric mode explained:

The numeric mode is based off of a binary representation of the permissions for user, group, and others, for more information please look at this explanation from Digital Ocean's community section:

• 4 stands for "read",
• 2 stands for "write",
• 1 stands for "execute", and
• 0 stands for "no permission."
• example 7 mean read + write + execute