Linux permissions

Binary Octal String representation Meaning
000 0 (0+0+0) - - - no permission
001 1 (0+0+1) - - x execute
010 2 (0+2+0) - w - write
011 3 (0+2+1) - w r write + execute
100 4 (4+0+0) r - - read
101 5 (4+0+1) r - x read + execute
110 6 (4+2+0) r w - read + write
111 7 (4+2+1) r w x read + write + execute

Permission structure (divided in 3 groups)

owner group other
r w r r w r - x
Permission Binary
r w x 4 + 3 + 1 = 7
r - - 4 + 2 + 0 = 6
r - x 4 + 0 + 1 = 5
Permission 765
r - read w - write / edit x - execute
4 - read 2 - write / edit 1 - execute

Commands


chmod 777 file –> full access for everyone
chmod 755 file –> owner full, other read + execute
chmod 644 file –> owner read + write, other read