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from: @(#)su.1 8.2 (Berkeley) 4/18/94
$NetBSD: su.1,v 1.17 2000/01/14 02:39:14 mjl Exp $
.Dd January 14, 2000 .Dt SU 1 .Os .Sh NAME .Nm su .Nd substitute user identity .Sh SYNOPSIS .Nm .Op Fl Kflm .Op Fl c Ar login-class .Op Ar login Op Ar "shell arguments" .Sh DESCRIPTION .Nm requests the Kerberos password for .Ar login (or for .Dq Ar login Ns .root , if no login is provided), and switches to that user and group ID after obtaining a Kerberos ticket granting ticket. A shell is then executed, and any additional .Ar "shell arguments" after the login name are passed to the shell. .Nm will resort to the local password file to find the password for .Ar login if there is a Kerberos error. If .Nm is executed by root, no password is requested and a shell with the appropriate user ID is executed; no additional Kerberos tickets are obtained.
p Alternatively, if the user enters the password "s/key", authentication will use the S/Key one-time password system as described in .Xr skey 1 . S/Key is a Trademark of Bellcore.
p By default, the environment is unmodified with the exception of .Ev USER , .Ev HOME , and .Ev SHELL . .Ev HOME and .Ev SHELL are set to the target login's default values. .Ev 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 target login's. This is the traditional behavior of .Nm "" .
p The options are as follows: l -tag -width Ds t Fl K Do not attempt to use Kerberos to authenticate the user. t Fl c Specify a login class. You may only override the default class if you're already root. t Fl f If the invoked shell is .Xr csh 1 , this option prevents it from reading the .Dq Pa .cshrc file. t Fl l Simulate a full login. The environment is discarded except for .Ev HOME , .Ev SHELL , .Ev PATH , .Ev TERM , and .Ev USER . .Ev HOME and .Ev SHELL are modified as above. .Ev USER is set to the target login. .Ev PATH is set to is set to the path specified in the
a /etc/login.conf file (or to the default of .Dq Pa /usr/bin:/bin:/usr/pkg/bin:/usr/local/bin ). .Ev TERM is imported from your current environment. The invoked shell is the target login's, and .Nm will change directory to the target login's home directory. t Fl Same as .Fl l t Fl 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 .Xr getusershell 3 ) and the caller's real uid is non-zero, .Nm will fail. .El
p The .Fl l and .Fl m options are mutually exclusive; the last one specified overrides any previous ones.
p Only users in group .Dq wheel (normally gid 0), as listed in
a /etc/group , can .Nm to .Dq root , unless group wheel does not exist or has no members. (If you do not want anybody to be able to .Nm to .Dq root , make .Dq root the only member of group .Dq wheel , which is the default.)
p By default (unless the prompt is reset by a startup file) the super-user prompt is set to .Dq Sy # to remind one of its awesome power. .Sh SEE ALSO .Xr csh 1 , .Xr login 1 , .Xr sh 1 , .Xr skey 1 , .Xr kinit 1 , .Xr kerberos 1 , .Xr setusercontext 3 , .Xr login.conf 5 , .Xr passwd 5 , .Xr group 5 , .Xr environ 7 .Sh ENVIRONMENT Environment variables used by .Nm "" : l -tag -width "HOME" t Ev HOME Default home directory of real user ID unless modified as specified above. t Ev PATH Default search path of real user ID unless modified as specified above. t Ev TERM Provides terminal type which may be retained for the substituted user ID. t Ev USER The user ID is always the effective ID (the target user ID) after an .Nm unless the user ID is 0 (root). .El .Sh HISTORY A .Nm command appeared in .At v7 .
Indexes created Wed Oct 22 13:09:56 GMT 2025