Understanding Linux File Permissions

In Linux, access to the files is controlled by the operating system using file permissions, attributes, and ownership. Understanding the Linux file system permissions model allows you to restrict access to files and directories only to authorized users and processes and make your system more secure.

Each file is owned by a particular user and a group and assigned with permission access rights for three different classes of users:

• The file owner.
• The group members.
• Others (everybody else).

There are three file permissions types that apply to each user class and allows you to specify which users are allowed to read the file, write to the file, or execute the file. The same permission attributes apply for both files and directories with a different meaning:

• The read permission.
• The file is readable. For example, when the read permission is set, the user can open the file in a text editor.
• The directory’s contents can be viewed. The user can list files inside the directory with the ls command.
• The write permission.
• The file can be changed or modified.
• The directory’s contents can be altered. The user can create new files , delete existing files , move files , rename files ..etc.
• The execute permission.
• The file can be executed.
• The directory can be entered using the cd command.

File permissions can be viewed using the ls command.