Monday, February 17, 2014

Permissions in Linux

Hello friends in this blog post I am discussing about permissions in Linux system. We have faced more time problem of reading, writing, and executing problems because of permissions. That is the owner of the particular file sets the permission who can read, write and execute it. In this blog we are just understanding how combinations of permissions to file or directory. In Linux there is only one root and other are administrators and normal user who having limited access or permissions. root user having complete authority to operate Linux system who is highest authority in Linux system. Administrator have also highest authority but not much authority like root user.

 
Linux system make groups of these users like root group contains only one user that is root. But in administrator group can have multiple administrator account. Also normal group can have multiple account of normal account like limited access account. Linux system have more groups available like dba, ssh etc.
Let's make note these three group:
  1. Root
  2. Administrator
  3. Normal
Now we will look for permissions of file or directory. look at following figure1.
Figure 1. Permissions
 As shown in above figure 1, first 10 characters indicates permissions for respective files. Lets take an example of default permissions given to file:

drwxr-xr--
In Linux system above permissions are given by default. We can modify them with the help of "chmod" shell command. Following figure 2 shows grouping of permissions of all above listed groups. 
Figure 2 Permission combinations