SU(1)

NAMN
su - change user ID or become superuser

SYNOPSIS

su [flaggor] [användarnamn]

BESKRIVNING

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.

Additional arguments may be provided after the username, in which case they are supplied to the user's login shell. In particular, an argument of -c will cause the next argument to be treated as a command by most command interpreters. The command will be executed by the shell specified in /etc/passwd for the target user.

Du kan använda argumentet -- för att separera flaggorna till su från de argument som skickas till skalet.

Användaren kommer att frågas efter ett lösenord, om det är lämpligt. Ogiltiga lösenord kommer att ge ett felmeddelande. Alla försök, både giltiga och ogiltiga, loggas för att detektera misskötsel av systemet.

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.

FLAGGOR

Flaggorna som gäller för kommandot su är:

-c, --command COMMAND
    Ange ett kommando som ska startas av skalet med -c.

-, -l, --login
    Tillhandahåll en miljö som liknar den som användaren skulle förvänta sig om användaren loggat in direkt.

    När - används måste den anges som den sista flaggan för su. De andra formerna (-l och --login) har inte denna restriktion.

-s, --shellSKAL
    Skalet som ska startas.

    The invoked shell is chosen from (highest priority first):

        Skalet angivet med --shell.

        Om --preserve-environment används, anges skalet med miljövariabeln $SHELL.

        The shell indicated in the /etc/passwd entry for the target user.

        /bin/sh om ett skal inte kunde hittas med någon ovanstående metod.

    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.

    Om målanvändaren har ett begränsat skal har denna flagga ingen effekt (såvida inte su har startats av 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.

TÄNK PÅ

Denna version av su har många kompileringsflaggor, kanske bara några används på specifika system.

CONFIGURATION

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.

FILER

/etc/passwd
    Användarkontoinformation.

/etc/shadow
    Säker användarkontoinformation.

/etc/login.defs
    Shadow password suite configuration.

AVSLUTNINGSVÄRDEN

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

SE OCKSÅ

login(1), login.defs(5), sg(1), sh(1).