Set Permissions Using Numeric Mode

• Permission Methods
  • Numeric Method
  • Symboolic Method
• -rwxr-x---. 1 user1 accounting 0 Jan 5 13:26 file.txt
  • If -rwxr-x--- starts witth a -, this means it is a file.
  • If it was a directory, we would see the letter D.
  • If it is a symbolic link, it would be an L.
  • If it is a character device, it would be a C.
  • If it is a pipe, it would be P
  • If it is a block device, then it would be B
    • Next 9 characters, would be rwxr-x---
      • User
      • Group Owner
      • Permission
    • First Group rwx is the User Owner of the file.
    • Next Group (r-x) is for the Group Owner.
    • Last Group (---) is for Permissions for Others.
      • People whom don’t belong to the group, everyone in the universe.
  • Must know the values of Read, Write and Execute
    • Read –> 4
    • Write –> 2
    • Execute –> 1
  • To add Read, Write and Execute for the owner.
    • 4 + 2 + 1 = 7
  • To set Read and Execute for the Group Owner:
    • 4 + 1 = 5
  • Other has no permissions, so is set to 0
  • Then to set the permissions for the above file.txt, we would use the values 750
  • Syntax for chmod –> Change Mode
    • chmod [options] <permissions> <filename>
    • chmod 750 file.txt
  • Initial permissions are assigned to a file, based on the value of the umask.
  • Use case for Recursive in Symbolic Mode.