Linux Chmod Command

synax: chmod options permissions filename

4 -> “read”,
2 -> “write”,
1 -> “execute”,
0 -> “no permission.”

u -> “current user”
g -> “group users”
o -> “other users”

a -> “all users”

r -> “read permission”
w -> “write permission”
x -> “execute permission”

Samples

• Add single permission to a file/directory

  $ chmod u+x filename

• Add multiple permission to a file/directory

  $ chmod u+r,g+x filename

• Remove permission from a file/directory

  $ chmod u-rx filename

• Change permission for all roles on a file/directory

  $ chmod a+x filename

• Make permission for a file same as another file (using reference)

  $ chmod --reference=file1 file2

• Apply the permission to all the files under a directory recursively
  Use option -R.

  $ chmod -R 755 directory-name/

• Change execute permission only on the directories (files are not affected)

  $ chmod u+X *