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28 .\" @(#)su.1 8.2 (Berkeley) 4/18/94
35 .Nd substitute user identity
41 .Op Ar login Op Ar args
45 utility requests appropriate user credentials via PAM
46 and switches to that user ID
47 (the default user is the superuser).
48 A shell is then executed.
50 PAM is used to set the policy
53 In particular, by default only users in the
55 group can switch to UID 0
57 This group requirement may be changed by modifying the
63 for details on how to modify this setting.
65 By default, the environment is unmodified with the exception of
73 are set to the target login's default values.
75 is set to the target login, unless the target login has a user ID of 0,
76 in which case it is unmodified.
77 The invoked shell is the one belonging to the target login.
78 This is the traditional behavior of
80 Resource limits and session priority applicable to the original user's
83 are also normally retained unless the target login has a user ID of 0.
85 The options are as follows:
88 Use the settings of the specified login class.
89 The login class must be defined in
91 Only allowed for the super-user.
93 If the invoked shell is
95 this option prevents it from reading the
99 Simulate a full login.
100 The environment is discarded except for
110 are modified as above.
112 is set to the target login.
115 .Dq Pa /bin:/usr/bin .
117 is imported from your current environment.
118 Environment variables may be set or overridden from the login class
119 capabilities database according to the class of the target login.
120 The invoked shell is the target login's, and
122 will change directory to the target login's home directory.
123 Resource limits and session priority are modified to that for the
124 target account's login class.
126 (no letter) The same as
129 Leave the environment unmodified.
130 The invoked shell is your login shell, and no directory changes are made.
131 As a security precaution, if the target user's shell is a non-standard
134 and the caller's real uid is
139 Set the MAC label to the user's default label as part of the user
141 Setting the MAC label may fail if the MAC label of the invoking process
142 is not sufficient to transition to the user's default MAC label.
143 If the label cannot be set,
154 options are mutually exclusive; the last one specified
155 overrides any previous ones.
159 are provided on the command line, they are passed to the login shell of
161 Note that all command line arguments before the target login name are
164 itself, everything after the target login name gets passed to the login
167 By default (unless the prompt is reset by a startup file) the super-user
170 to remind one of its awesome power.
172 Environment variables used by
176 Default home directory of real user ID unless modified as
179 Default search path of real user ID unless modified as specified above.
181 Provides terminal type which may be retained for the substituted
184 The user ID is always the effective ID (the target user ID) after an
186 unless the user ID is 0 (root).
189 .Bl -tag -width "/etc/pam.d/su" -compact
191 PAM configuration for
195 .Bl -tag -width 5n -compact
196 .It Li "su -m operator -c poweroff"
197 Starts a shell as user
201 You will be asked for operator's password unless your real UID is 0.
204 option is required since user
206 does not have a valid shell by default.
209 is passed to the shell of the user
211 and is not interpreted as an argument to
213 .It Li "su -m operator -c 'shutdown -p now'"
214 Same as above, but the target command consists of more than a
215 single word and hence is quoted for use with the
217 option being passed to the shell.
218 (Most shells expect the argument to
220 to be a single word).
221 .It Li "su -m -c staff operator -c 'shutdown -p now'"
222 Same as above, but the target command is run with the resource limits of
225 Note: in this example, the first
229 while the second is an argument to the shell being invoked.
231 Simulate a login for user foo.
235 Simulate a login for root.