File permission in Linux

I am running with Linux RH5 operating system and new for this operating system and need to know some basic things about file permission. i want keep secure my personal file in the network.I think someone can access my files and need to prevent the access from the files.I need your instructions to achieve this task.Your help would be appreciated.

Thanks you.

File permission in Linux :

In the Linux operating system, Each file belongs to a particular user and group and other.The other refers to that user which is not the owner of file nor the member of that group.

Commonly,permissions are the controlled by three world Read,Write,Execute.According to this permission,the files are dispersed in the system or network.

Read permission on file :

The owner of file or the Root can grant access on the file in Linux.I am going to explore the procedure of granting the Read permission on file.

Enter into your account and permit the write access of files to Other users :

$ chmod o+r my_file.txt /* Write access to the others
$ chmod g+r my_file.txt /* Write access to Group

The Chmod command is being used to change the mode of file.

Write permission in Linux :

The write operation can be performed when the owner of file want to grant.The owner of the file can prevent your self using chmod command with U option.Here is an example which is granting the write access to others and group.

$ chmod o+w my_file.txt
$ chmod g+w my_file.txt

The w word specifies the Read permission on the file to group and others respectively.

Execute permission on File :

The execute permission specifies that a user can view and use of file for other task.The execute permission is granted with x word and associate the name of file.An example is given below :

$ chmod o-x sneak.txt
$ chmod o-x sneak.txt

You can specify the Others and Group together for permission for particular file.

Changing Permissions With Numbers :

Linux provide another way to change permission of files which is dependent on the calculation of number.The number are here against permission :

Read [r - 4]
Write [w- 2]
Execute [x - 1]
Nothing [- - 0]

You can use these number grant the permission with calculation.I am going to show an example in which I will grant read and write permission to others on Lillber.txt .

$ chmod 006 Lillber.txt