z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

su
v Changes the group ID. If a user ID is specified, the group ID is changed to that
of the specified user’s default group GID.
If a user ID is specified, the supplementary group list is changed to that of the
specified user.
If the change of group ID or supplemental group list fails, the su command
issues a message and continues.
v Changes the user ID. Your user ID may be changed to either the specified user
ID or the superuser’s user ID (UID 0).
– When a user ID is specified, your MVS identity changes to the specified user
ID, changing your access authority for MVS data sets in addition to changing
to the new user’s UID.
– When a user ID is not specified, your MVS identity remains the same. This
maintains your access authority to MVS data sets, while gaining superuser
authority.
– If you are already running under UID 0 and BPX.DAEMON is defined, issuing
su with no userid will result in your UID being switched to BPXROOT. If
BPX.DAEMON is not defined, and you issue su with the userid while running
under UID 0, your UID will remain set to 0. In both cases, access to the
BPX.SUPERUSER resource in the FACILITY class will not be checked.
v Sets up the shell environment.
If the login shell (’–’ flag) is specified, the OMVS segment of the new user is
used to set up the shell environment, similar to user login processing. This
includes setting the SHELL, HOME, and LOGNAME environment variables.
PATH is set to the system default (/bin), TERM is preserved from the current
environment, and STEPLIB is set to ″none″. Other environment variables are not
inherited by the new shell.
If the login shell is not specified, the OMVS segment of your user profile is used
to set up the shell environment. The environment is set up to be as similar as
possible to the environment of the shell issuing the su command. Existing values
of HOME, LOGNAME, and PATH are preserved. If not set in the current shell
environment, HOME and LOGNAME are set from the calling user’s profile, and
PATH is set to the system default (/bin). SHELL is set to calling user’s profile
value, or the default /bin/sh, if not defined.
v Executes the new shell. If login shell (’–’ flag) is specified, prepend ’–’ to the
shell’s name. This indicates that the shell should read its login startup files (for
example, /bin/sh will read /etc/profile and $HOME/.profile). The new shell is
initialized to run as a child process of the shell issuing the su command. If the su
command is run from a restricted shell (such as a shell that was started with the
–r option), you will exit from the restricted shell and leave the protection of the
trusted environment.
Notes:
1. The new shell is always run in a new address space, even if you have
_BPX_SHAREAS=YES set.
2. If you use the OMVS interface when running a shell created by su, any
attempt to execute TSO commands (PF6) results in the command running
back in your TSO address space. When these TSO commands run, they run
with your TSO identity, not the identity specified by su.
608 z/OS V1R9.0 UNIX System Services Command Reference
However, if you are not using the OMVS interface (for example, you rlogin or
telnet into the shell), you cannot use PF6 to execute a TSO command, and,
as a result, there will be no TSO address space or identity. The alternative
solution is to use tso –t which allows you to run a TSO/E command with the
current identity set by su.