Provided by: login_220.127.116.11+svn3283-3ubuntu5_amd64
su - change user ID or become superuser
su [opzioni] [username]
The su command is used to become another user during a login session. Invoked without a username, su defaults to becoming the superuser. The optional argument - may be used to provide an environment similar to what the user would expect had the user logged in directly. Dopo il nome utente, è possibile specificare argomenti aggiuntivi da passare alla shell di login dell'utente. In particolare, molti interpreti di comando adottano la convenzione per cui l'opzione -c seguita da un argomento fa sì che quest'ultimo sia considerato un comando.Il comando viene eseguito dalla shell specificata in /etc/passwd per l'utente di destinazione. You can use the -- argument to separate su options from the arguments supplied to the shell. All'utente viene quindi chiesta la password, se necessario. Una password errata viene segnalata da un messaggio d'errore. Viene effettuato il log di tutti i tentativi, siano essi riusciti o meno, al fine di rilevare ogni abuso del sistema. The current environment is passed to the new shell. The value of $PATH is reset to /bin:/usr/bin for normal users, or /sbin:/bin:/usr/sbin:/usr/bin for the superuser. This may be changed with the ENV_PATH and ENV_SUPATH definitions in /etc/login.defs. A subsystem login is indicated by the presence of a "*" as the first character of the login shell. The given home directory will be used as the root of a new file system which the user is actually logged into.
Il comando su accetta le seguenti opzioni: -c, --command COMMAND Specify a command that will be invoked by the shell using its -c. -, -l, --login Provide an environment similar to what the user would expect had the user logged in directly. When - is used, it must be specified as the last su option. The other forms (-l and --login) do not have this restriction. -s, --shell SHELL The shell that will be invoked. The invoked shell is chosen from (highest priority first): The shell specified with --shell. If --preserve-environment is used, the shell specified by the $SHELL environment variable. The shell indicated in the /etc/passwd entry for the target user. /bin/sh if a shell could not be found by any above method. If the target user has a restricted shell (i.e. the shell field of this user's entry in /etc/passwd is not listed in /etc/shell), then the --shell option or the $SHELL environment variable won't be taken into account, unless su is called by root. -m, -p, --preserve-environment Preserve the current environment, except for: $PATH reset according to the /etc/login.defs options ENV_PATH or ENV_SUPATH (see below); $IFS reset to «<space><tab><newline>», if it was set. If the target user has a restricted shell, this option has no effect (unless su is called by root). Note that the default behavior for the environment is the following: The $HOME, $SHELL, $USER, $LOGNAME, $PATH, and $IFS environment variables are reset. If --login is not used, the environment is copied, except for the variables above. If --login is used, the $TERM, $COLORTERM, $DISPLAY, and $XAUTHORITY environment variables are copied if they were set. Other environments might be set by PAM modules.
Questa versione di su ha molte opzioni di compilazione; solo una parte di esse potrebbe essere in uso su un determinato sistema.
The following configuration variables in /etc/login.defs change the behavior of this tool: CONSOLE_GROUPS (string) List of groups to add to the user's supplementary groups set when logging in on the console (as determined by the CONSOLE setting). Default is none. Use with caution - it is possible for users to gain permanent access to these groups, even when not logged in on the console. DEFAULT_HOME (boolean) Indicate if login is allowed if we can't cd to the home directory. Default in no. If set to yes, the user will login in the root (/) directory if it is not possible to cd to her home directory. ENV_PATH (string) If set, it will be used to define the PATH environment variable when a regular user login. The value can be preceded by PATH=, or a colon separated list of paths (for example /bin:/usr/bin). The default value is PATH=/bin:/usr/bin. ENV_SUPATH (string) If set, it will be used to define the PATH environment variable when the superuser login. The value can be preceded by PATH=, or a colon separated list of paths (for example /sbin:/bin:/usr/sbin:/usr/bin). The default value is PATH=/sbin:/bin:/usr/sbin:/usr/bin. SULOG_FILE (string) If defined, all su activity is logged to this file. SU_NAME (string) If defined, the command name to display when running "su -". For example, if this is defined as "su" then a "ps" will display the command is "-su". If not defined, then "ps" would display the name of the shell actually being run, e.g. something like "-sh". SYSLOG_SU_ENAB (boolean) Enable "syslog" logging of su activity - in addition to sulog file logging.
/etc/passwd informazioni sugli account utente. /etc/shadow Informazioni sicure sugli account di utenti. /etc/login.defs Shadow password suite configuration.
On success, su returns the exit value of the command it executed. If this command was terminated by a signal, su returns the number of this signal plus 128. If su has to kill the command (because it was asked to terminate, and the command did not terminate in time), su returns 255. Some exit values from su are independent from the executed command: 0 success (--help only) 1 System or authentication failure 126 The requested command was not found 127 The requested command could not be executed
login(1), login.defs(5), sg(1), sh(1).