OWNER GROUP OTHERS
400 200 100 40 20 10 4 2 1
read write execute read write execute read write execute# everyone can read/write/execute
rwxrwxrwx chmod 777 filename
# everyone can read/execute
# only owner can read/write/execute
rwxr-xr-x chmod 755 filename
# everyone can read
# only owner can write
rw-r--r-- chmod 664 filename
# only owner can read/write
rw------- chmod 600 filename