Fedora Linux

Control Access to Files

All Linux and Unix systems use file permissions or modes to control access to files. Fedora extends this with the user-private-group scheme, which simplifies the configuration of permissions for collaboration.

Tip

There are two other mechanisms available for file access control: see Lab 8.2, “Using SELinux” and Lab 8.3, “Using Access Control Lists.”

How Do I Do That?

There are three basic file permissions:

read (r)

Grants permission to access the contents of a file. There are no restrictions on what can be done with the file contents, so read permission includes permission to view or process the contents of the file, as well as permission to copy the file. On a directory, read permission enables the display of the list of files in the directory; without read permission, you can access a file contained in the directory only if you know the exact name of the file.

write (w)

Grants permission to write to a file; this includes overwriting existing information, append to the end of the file, and truncate (shorten) the file. On a directory, write permission enables the creation and deletion of files within that directory.

execute (x)

Grants permission to execute the file. If the file is a binary, it can be executed by the kernel; if it is a text file, it is treated as a script. On a directory, execute permission grants access to the contents of the directory (some people refer to execute permission on a directory as search, or passthrough, permission).

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