System Administration Guide: Security Services

UNIX File Permissions

The following table lists and describes the permissions that you can give to each class of user for a file or directory.

Table 6–2 File and Directory Permissions


Symbol	Permission	Object	Description
`r`	Read	File	Designated users can open and read the contents of a file.
		Directory	Designated users can list files in the directory.
`w`	Write	File	Designated users can modify the contents of the file or delete the file.
		Directory	Designated users can add files or add links in the directory. They can also remove files or remove links in the directory.
`x`	Execute	File	Designated users can execute the file, if it is a program or shell script. They also can run the program with one of the `exec(2)` system calls.
		Directory	Designated users can open files or execute files in the directory. They also can make the directory and the directories beneath it current.
`-`	Denied	File and Directory	Designated users cannot read, write, or execute the file.

These file permissions apply to regular files, and to special files such as devices, sockets, and named pipes (FIFOs).

For a symbolic link, the permissions that apply are the permissions of the file that the link points to.

You can protect the files in a directory and its subdirectories by setting restrictive file permissions on that directory. Note, however, that superuser has access to all files and directories on the system.