The
su
utility requests appropriate user credentials via PAM
and switches to that user ID
(the default user is the superuser).
A shell is then executed.
PAM is used to set the policy
su(1)
will use.
In particular, by default only users in the
"wheel"
group can switch to UID 0
("root").
This group requirement may be changed by modifying the
"pam_group"
section of
/etc/pam.d/su.
See
pam_group(8)
for details on how to modify this setting.
By default, the environment is unmodified with the exception of
USER,
HOME,
and
SHELL.
HOME
and
SHELL
are set to the target login's default values.
USER
is set to the target login, unless the target login has a user ID of 0,
in which case it is unmodified.
The invoked shell is the one belonging to the target login.
This is the traditional behavior of
su.
Resource limits and session priority applicable to the original user's
login class (see
login.conf(5))
are also normally retained unless the target login has a user ID of 0.
The options are as follows:
|
| -c class
|
| |
Use the settings of the specified login class.
The login class must be defined in
login.conf(5).
Only allowed for the super-user.
|
| -f
|
| |
If the invoked shell is
csh(1),
this option prevents it from reading the
" .cshrc"
file.
|
| -l
|
| |
Simulate a full login.
The environment is discarded except for
HOME,
SHELL,
PATH,
TERM,
and
USER.
HOME
and
SHELL
are modified as above.
USER
is set to the target login.
PATH
is set to
" /bin:/usr/bin".
TERM
is imported from your current environment.
Environment variables may be set or overridden from the login class
capabilities database according to the class of the target login.
The invoked shell is the target login's, and
su
will change directory to the target login's home directory.
Resource limits and session priority are modified to that for the
target account's login class.
|
| -
|
(no letter) The same as
-l.
|
| -m
|
| |
Leave the environment unmodified.
The invoked shell is your login shell, and no directory changes are made.
As a security precaution, if the target user's shell is a non-standard
shell (as defined by
getusershell(3))
and the caller's real uid is
non-zero,
su
will fail.
|
| -s
|
| |
Set the MAC label to the user's default label as part of the user
credential setup.
Setting the MAC label may fail if the MAC label of the invoking process
is not sufficient to transition to the user's default MAC label.
If the label cannot be set,
su
will fail.
|
|
The
-l
(or
-)
and
-m
options are mutually exclusive; the last one specified
overrides any previous ones.
If the optional
args
are provided on the command line, they are passed to the login shell of
the target login.
Note that all command line arguments before the target login name are
processed by
su
itself, everything after the target login name gets passed to the login
shell.
By default (unless the prompt is reset by a startup file) the super-user
prompt is set to
" amp;#"
to remind one of its awesome power.
