PERMISSION IN LINUX

PERMISSION

Permission have two type

                1) Symbolic method (owner u, group g, other o)

                2) Numerical method (owner, group, other)

Mainly Read (r=4) write (w=2) execute (x=1)

Permission is 4 2 1 according to the Umask.

To check the umask or change

                     # vim /etc/bashrc

To give the permission according to the symbolic method

                     #chmod g+w file name

Note:- default permission on directory is 755 and on the file is 644.

                      #chmod 755 directory name

Advance permission

                             1)      Sticky bit                  =1

                             2)      SGID (set group ID) = 2

                             3)      SUID (set user ID)   =4

Sticky Bit

This permission is use to prevents users for deleting each other file even they have full rights to access the directory.

                        #chmod 1757 file name

SGID

It is use to create collaborate directory. This provide a mechanism to allow on level access to user who are member of the same group that owns the directory while a different level of access to non-user of file in the directory.

                         #chmod 2757 directory name

SUID

This permission implement on user only. This permission allow a local user to work in the root privilege mode on the particular command. This permission is set on the command location.

                           #chmod 4755 /usr/bin/passwd

By defaults the permission on user home directory is 700.