working with permissions on unix

UNIX assigns file permissions to three broad categories:

- The user that owns the file

- The group that owns the file

- Everyone else (a.k.a 'world' or 'other')

Each permission category can be assigned three permissions:

- (r)ead

- (w)rite

- e(x)ecute

UNIX permissions can be represented as symbols and as octal digits

    

Type of files that are presently categories in Linux are as below:

Below is the crucial understanding of output that you normally see in command "ls -l"

--------------------------------------------------------------------------

Adding Read permission to User/Owner

# chmod u+r /tmp/user1.txt

Adding Write permission to User/Owner

# chmod u+w /tmp/user1.txt

Adding Execute permission to User/Owner

# chmod u+x /tmp/user1.txt

--------------------------------------------------------------------------

Adding Read permission to Group

# chmod g+r /tmp/user1.txt




Adding Write permission to Group

# chmod g+w /tmp/user1.txt




Adding Execute permission to Group

# chmod g+x /tmp/user1.txt

--------------------------------------------------------------------------

Adding Read permission to Other/World

# chmod o+r /tmp/user1.txt

Adding Write permission to Other/World

# chmod o+w /tmp/user1.txt

Adding Execute permission to Other/World

# chmod o+x /tmp/user1.txt

--------------------------------------------------------------------------

Assigning Execute permission to Group and Other/World

# chmod 011 /tmp/user1.txt




Assigning Write permission to Group and Other/World

# chmod 022 /tmp/user1.txt

Assigning Write + Execute permission to Group and Other/World

# chmod 033 /tmp/user1.txt




Assigning Read permission to Group and Other/World 

# chmod 044 /tmp/user1.txt

Assigning Read + Execute permission to Group and Other/World

# chmod 055 /tmp/user1.txt




Assigning Read + Write permission to Group and Other/World

# chmod 066 /tmp/user1.txt

Assigning Read +Write + Execute permission to Group and Other/World 

# chmod 077 /tmp/user1.txt

--------------------------------------------------------------------------

Assigning Execute permission to Group

# chmod 010 /tmp/user1.txt







Assigning Write permission to Group

# chmod 020 /tmp/user1.txt







Assigning Write + Execute permission to Group

# chmod 030 /tmp/user1.txt




Assigning Read permission to Group

# chmod 040 /tmp/user1.txt




Assigning Read + Execute permission to Group

# chmod 050 /tmp/user1.txt




Assigning Read + Write permission to Group

# chmod 060 /tmp/user1.txt




Assigning Read + Write + Execute permission to Group

# chmod 070 /tmp/user1.txt

--------------------------------------------------------------------------

Assigning Write + Execute permission to Other/World

# chmod 001 /tmp/user1.txt




Assigning Write + Execute permission to Other/World

# chmod 002 /tmp/user1.txt




Assigning Write + Execute permission to Other/World

# chmod 003 /tmp/user1.txt




Assigning Read permission to Other/World 

# chmod 004 /tmp/user1.txt




Assigning Read + Execute permission to Other/World

# chmod 005 /tmp/user1.txt




Assigning Read + Write permission to Other/World

# chmod 006 /tmp/user1.txt




Assigning Read + Write + Execute permission to Other/World

# chmod 007 /tmp/user1.txt

--------------------------------------------------------------------------

Assigning Execute permission to User/Owner , Group and Other/World

# chmod 111 /tmp/user1.txt




Assigning Write permission to User/Owner , Group and Other/World

# chmod 222 /tmp/user1.txt




Assigning Write + Execute permission to User/Owner , Group and Other/World

# chmod 333 /tmp/user1.txt

Assigning Read + Write + Execute permission to User/Owner , Group and Other/World

# chmod 444 /tmp/user1.txt




Assigning Read + Execute permission to User/Owner , Group and Other/World

# chmod 555 /tmp/user1.txt




Assigning Read + Write permission to User/Owner , Group and Other/World

# chmod 666 /tmp/user1.txt




Assigning Read + Write + Execute permission to User/Owner , Group and Other/World

# chmod 777 /tmp/user1.txt




--------------------------------------------------------------------------

Assigning Execute permission to User/Owner and Group

# chmod 110 /tmp/user1.txt

Assigning Write permission to User/Owner and Group

# chmod 220 /tmp/user1.txt




Assigning Write + Execute permission to User/Owner and Group

# chmod 330 /tmp/user1.txt




Assigning Read permission to User/Owner , Group

# chmod 440 /tmp/user1.txt




Assigning Read + Execute permission to User/Owner and Group

# chmod 055 /tmp/user1.txt




Assigning Read + Write permission to User/Owner and Group

# chmod 066 /tmp/user1.txt




Assigning Read + Write + Execute permission to User/Owner and Group

# chmod 770 /tmp/user1.txt




--------------------------------------------------------------------------

Assigning Execute permission to User/Owner and Other/World 

# chmod 101 /tmp/user1.txt




Assigning Write permission to User/Owner and Other/World 

# chmod 202 /tmp/user1.txt




Assigning Write + Execute permission to User/Owner and Other/World 

# chmod 303 /tmp/user1.txt

 Assigning Read permission to User/Owner and Other/World

# chmod 404 /tmp/user1.txt




Assigning Read + Execute permission to User/Owner and Other/World

# chmod 505 /tmp/user1.txt




Assigning Read + Write permission to User/Owner and Other/World

# chmod 606 /tmp/user1.txt




Assigning Read + Write + Execute permission to User/Owner and Other/World

# chmod 707 /tmp/user1.txt




--------------------------------------------------------------------------

Assigning Execute permission to User/Owner

# chmod 100 /tmp/user1.txt

Assigning Write permission to User/Owner

# chmod 200 /tmp/user1.txt

Assigning Write + Execute permission to User/Owner

# chmod 300 /tmp/user1.txt

Assigning Read permission to User/Owner

# chmod 400 /tmp/user1.txt




Assigning Read + Execute permission to User/Owner

# chmod 500 /tmp/user1.txt




Assigning Read + Write permission to User/Owner

# chmod 600 /tmp/user1.txt




Assigning Read + Group + Execute permission to User/Owner

# chmod 700 /tmp/user1.txt




--------------------------------------------------------------------------

Adding SUID to a file without execution permission to Group 

# chmod u+s /tmp/user1.txt




Assigning SUID permission to file with no execute permission to user

# chmod 3444 /tmp/user1.txt

Adding SUID permission to file having execute permissions to User/Owner

# chmod u+s /tmp/user1.txt

Assiging SUID permission to file having execute permissions to User/Owner

# chmod 3755 /tmp/user1.txt