su(1) — Commands
NAME
su − Substitutes user ID temporarily
SYNOPSIS
su [−f] | [−c command] | [−] [user]
FLAGS
−c command
Executes the specified command in the user’s shell.
−fPrevents the user’s shell initialization file from being executed by passing the −f option to the user’s shell, thus making su start up faster.
−Simulates a full login by executing the commands in either the .cshrc and .login files for csh or the .profile file for sh and ksh and by setting the current working directory to the user’s home directory.
DESCRIPTION
The su command demands the password of the specified user, and if it is given, changes to that user and invokes the user’s shell without changing the current directory.
The user environment is unchanged except for HOME and SHELL, which are taken from the password file for the user being substituted (see environ). The new user ID stays in force until the shell exits.
If no user ID is specified, su attempts to transition to the root account.
The process created as a result of the su does not assume the privilege environment of the destination user; the discretionary identity of the process is changed and the privileges are reduced to the intersection of the two users. The power you gain is not as great as that of the superuser on a nonsecure system.
Security Restrictions
The su command fails if any lock conditions exist on the target account. Specifically, if the destination account was retired, if the number of unsuccessful login attempts exceeds the maximum allowed, if the administrative lock was applied, or the password’s lifetime was exceeded, the Information System Security Officer (ISSO) must unlock the destination account before any user can log in to it or use su to transition to it. The base privileges of the new process are adjusted to the intersection of those of the source and destination accounts. Thus, you cannot gain any base privileges by using su. Specifically, su to root does not gain the power that it once did.
Note that command authorizations are checked against the process login user ID. Thus, using su to transition to another account does not gain you that account’s command authorizations. Similarly, the new process’s kernel authorizations are set to the intersection of the source and target account. The system’s audit subsystem audits your actions relative to the login user ID.
Security Configuration
The su command is modified in all security configurations of the system.
SECURITY NOTE
This security-sensitive command uses the SIA (Security Integration Architecture) routine as an interface to the security mechanisms. See the matrix.conf(4) reference page for more information.
RELATED INFORMATION
Files: sialog(4)