su(1)
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SU(1) NetBSD General Commands Manual SU(1)
NAME
su - substitute user identity
SYNOPSIS
su [-Kdflm] [-c login-class] [login [shell arguments]]
DESCRIPTION
su requests the Kerberos password for login (or for ``login.root'', if no
login is provided), and switches to that user and group ID after obtain-
ing a Kerberos ticket granting ticket. A shell is then executed, and any
additional shell arguments after the login name are passed to the shell.
su will resort to the local password file to find the password for login
if there is a Kerberos error. If su is executed by root, no password is
requested and a shell with the appropriate user ID is executed; no addi-
tional Kerberos tickets are obtained.
Alternatively, if the user enters the password "s/key", authentication
will use the S/Key one-time password system as described in skey(1).
S/Key is a Trademark of Bellcore.
By default, the environment is unmodified with the exception of USER,
HOME, SHELL, and SU_FROM. 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. SU_FROM is set to
the caller's login. The invoked shell is the target login's. With the
exception of SU_FROM this is the traditional behavior of su.
The options are as follows:
-K Do not attempt to use Kerberos to authenticate the user.
-c Specify a login class. You may only override the default class
if you're already root. See login.conf(5) for details.
-d Same as -l, but does not change the current directory.
-f If the invoked shell is csh(1), this option prevents it from
reading the ``.cshrc'' file. If the invoked shell is sh(1), or
ksh(1), this option unsets ENV, thus preventing the shell from
executing the startup file pointed to by this variable.
-l Simulate a full login. The environment is discarded except for
HOME, SHELL, PATH, TERM, USER, and SU_FROM. HOME, SHELL, and
SU_FROM are modified as above. USER is set to the target login.
PATH is set to the path specified in the /etc/login.conf file (or
to the default of ``/usr/bin:/bin:/usr/pkg/bin:/usr/local/bin''
). TERM is imported from your current environment. The invoked
shell is the target login's, and su will change directory to the
target login's home directory.
- 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.
The -l and -m options are mutually exclusive; the last one specified
overrides any previous ones.
Only users in group ``wheel'' (normally gid 0), as listed in /etc/group,
can su to ``root'', unless group wheel does not exist or has no members.
(If you do not want anybody to be able to su to ``root'', make ``root''
the only member of group ``wheel'', which is the default.)
For sites with very large user populations, group ``wheel'' can contain
the names of other groups that will be considered authorized to su to
``root''.
By default (unless the prompt is reset by a startup file) the super-user
prompt is set to ``#'' to remind one of its awesome power.
COMPILATION OPTIONS
Several compilation time options are available that alter the program's
behavior. These options are:
SU_GROUP If defined, it changes the default group that is
allowed to become ``root'' from ``wheel'' to the spec-
ified string.
SU_ROOTAUTH If defined, it specifies a group whose members are
allowed to become ``root'' by supplying their own
password instead of the ``root'' one.
SU_INDIRECT_GROUP If defined, the SU_GROUP and SU_ROOTAUTH groups are
treated as indirect groups. The group members of
those two groups are treated as groups themselves.
EXIT STATUS
su returns the exit status of the executed subshell, or 1 if any error
occurred while switching privileges.
ENVIRONMENT
Environment variables used by su:
HOME Default home directory of real user ID unless modified as specified
above.
PATH Default search path of real user ID unless modified as specified
above.
TERM Provides terminal type which may be retained for the substituted
user ID.
USER The user ID is always the effective ID (the target user ID) after
an su unless the user ID is 0 (root).
EXAMPLES
To become user username and use the same environment as in original
shell, execute:
su username
To become user username and use environment as if full login would be
performed, execute:
su -l username
When a -c option is included after the login name it is not a su option,
because any arguments after the login are passed to the shell. (See
csh(1), ksh(1) or sh(1) for details.) To execute arbitrary command with
privileges of user username, execute:
su username -c "command args"
SEE ALSO
csh(1), kinit(1), login(1), sh(1), skey(1), setusercontext(3), group(5),
login.conf(5), passwd(5), environ(7), kerberos(8)
HISTORY
A su command existed in Version 5 AT&T UNIX (and probably earlier).
NetBSD 2.0.2 August 20, 2003 NetBSD 2.0.2
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