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Switch user ID (UNIX)


su [-c] [[-] userid [arguments]]

Runs on:



Pass the specified list of arguments to the shell.
Switch to the specified user ID. If preceeded by the - argument, userid's login scripts will run, setting up the shell environment as if you had actually logged in as the specified user.


The su utility lets you temporarily become another user, then return to your regular userid.

The su utility requests the password of the given userid (root, by default) and changes to that userid, invoking its shell but modifying only essential elements of the environment. Only the HOME, PATH, and possibly SHELL environment variables are changed, but the new shell has the rights and privileges of the user specified. The new userid remains in effect until this shell exits.

Note: This utility needs to have the setuid (“set user ID”) bit set in its permissions. If you use mkefs, mketfs, or mkifs on a Windows host to include this utility in an image, use the perms attribute to specify its permissions explicitly, and the uid and gid attributes to set the ownership correctly.


Korn shell command interpreter.
The bit bucket.
This file is used to lock password files when modifications are taking place.
Logs system accounting information.
The passwd utility copies this file as a user's initial .profile when it creates a new account.
Defines the known groups for the system.
Defines the valid user IDs on the system.
Contains encoded versions of the actual passwords for user accounts. The passwords themselves aren't stored in the /etc/passwd file.
Records all su activity.

See also:

login, passwd

Logging In, Logging Out, and Shutting Down in the Neutrino User's Guide