SUDO(1m)                     System Manager's Manual                    SUDO(1m)

NAME
     sudo, sudoedit - execute a command as another user

SYNOPSIS
     sudo -h | -K | -k | -V
     sudo -v [-AknS] [-a auth__type] [-g group name | #gid] [-p prompt]
          [-u user name | #uid]
     sudo -l[_l] [-AknS] [-a auth__type] [-g group name | #gid] [-p prompt]
          [-U user name] [-u user name | #uid] [command]
     sudo [-AbEHnPS] [-a auth__type] [-C fd] [-c class | _-]
          [-g group name | #gid] [-p prompt] [-r role] [-t type]
          [-u user name | #uid] [VAR=value] -i | -s [command]
     sudoedit [-AnS] [-a auth__type] [-C fd] [-c class | _-]
              [-g group name | #gid] [-p prompt] [-u user name | #uid] file
              ...

DESCRIPTION
     sudo allows a permitted user to execute a command as the superuser or
     another user, as specified by the security policy.

     sudo supports a plugin architecture for security policies and
     input/output logging.  Third parties can develop and distribute their own
     policy and I/O logging plugins to work seamlessly with the sudo front
     end.  The default security policy is sudoers, which is configured via the
     file /etc/sudoers, or via LDAP.  See the PLUGINS section for more
     information.

     The security policy determines what privileges, if any, a user has to run
     sudo.  The policy may require that users authenticate themselves with a
     password or another authentication mechanism.  If authentication is
     required, sudo will exit if the user's password is not entered within a
     configurable time limit.  This limit is policy-specific; the default
     password prompt timeout for the sudoers security policy is 5 minutes.

     Security policies may support credential caching to allow the user to run
     sudo again for a period of time without requiring authentication.  The
     sudoers policy caches credentials for 5 minutes, unless overridden in
     sudoers(4).  By running sudo with the -v option, a user can update the
     cached credentials without running a command.

     When invoked as sudoedit, the -e option (described below), is implied.

     Security policies may log successful and failed attempts to use sudo.  If
     an I/O plugin is configured, the running command's input and output may
     be logged as well.

     The options are as follows:

     -A          Normally, if sudo requires a password, it will read it from
                 the user's terminal.  If the -A (askpass) option is
                 specified, a (possibly graphical) helper program is executed
                 to read the user's password and output the password to the
                 standard output.  If the SUDO_ASKPASS environment variable is
                 set, it specifies the path to the helper program.  Otherwise,
                 if /etc/sudo.conf contains a line specifying the askpass
                 program, that value will be used.  For example:

                     # Path to askpass helper program
                     Path askpass /usr/X11R6/bin/ssh-askpass

                 If no askpass program is available, sudo will exit with an
                 error.

     -a type     The -a (authentication type) option causes sudo to use the
                 specified authentication type when validating the user, as
                 allowed by /etc/login.conf.  The system administrator may
                 specify a list of sudo-specific authentication methods by
                 adding an ``auth-sudo'' entry in /etc/login.conf.  This
                 option is only available on systems that support BSD
                 authentication.

     -b          The -b (background) option tells sudo to run the given
                 command in the background.  Note that if you use the -b
                 option you cannot use shell job control to manipulate the
                 process.  Most interactive commands will fail to work
                 properly in background mode.

     -C fd       Normally, sudo will close all open file descriptors other
                 than standard input, standard output and standard error.  The
                 -C (close from) option allows the user to specify a starting
                 point above the standard error (file descriptor three).
                 Values less than three are not permitted.  The security
                 policy may restrict the user's ability to use the -C option.
                 The sudoers policy only permits use of the -C option when the
                 administrator has enabled the closefrom__override option.

     -c class    The -c (class) option causes sudo to run the specified
                 command with resources limited by the specified login class.
                 The class argument can be either a class name as defined in
                 /etc/login.conf, or a single `-' character.  Specifying a
                 class of - indicates that the command should be run
                 restricted by the default login capabilities for the user the
                 command is run as.  If the class argument specifies an
                 existing user class, the command must be run as root, or the
                 sudo command must be run from a shell that is already root.
                 This option is only available on systems with BSD login
                 classes.

     -E          The -E (preserve environment) option indicates to the
                 security policy that the user wishes to preserve their
                 existing environment variables.  The security policy may
                 return an error if the -E option is specified and the user
                 does not have permission to preserve the environment.

     -e          The -e (edit) option indicates that, instead of running a
                 command, the user wishes to edit one or more files.  In lieu
                 of a command, the string "sudoedit" is used when consulting
                 the security policy.  If the user is authorized by the
                 policy, the following steps are taken:

                  1.   Temporary copies are made of the files to be edited
                       with the owner set to the invoking user.

                  2.   The editor specified by the policy is run to edit the
                       temporary files.  The sudoers policy uses the
                       SUDO_EDITOR, VISUAL and EDITOR environment variables
                       (in that order).  If none of SUDO_EDITOR, VISUAL or
                       EDITOR are set, the first program listed in the editor
                       sudoers(4) option is used.

                  3.   If they have been modified, the temporary files are
                       copied back to their original location and the
                       temporary versions are removed.

                 If the specified file does not exist, it will be created.
                 Note that unlike most commands run by sudo, the editor is run
                 with the invoking user's environment unmodified.  If, for
                 some reason, sudo is unable to update a file with its edited
                 version, the user will receive a warning and the edited copy
                 will remain in a temporary file.

     -g group    Normally, sudo runs a command with the primary group set to
                 the one specified by the password database for the user the
                 command is being run as (by default, root).  The -g (group)
                 option causes sudo to run the command with the primary group
                 set to group instead.  To specify a gid instead of a group
                 name, use #gid.  When running commands as a gid, many shells
                 require that the `#' be escaped with a backslash (`\').  If
                 no -u option is specified, the command will be run as the
                 invoking user (not root).  In either case, the primary group
                 will be set to group.

     -H          The -H (HOME) option requests that the security policy set
                 the HOME environment variable to the home directory of the
                 target user (root by default) as specified by the password
                 database.  Depending on the policy, this may be the default
                 behavior.

     -h          The -h (help) option causes sudo to print a short help
                 message to the standard output and exit.

     -i [command]
                 The -i (simulate initial login) option runs the shell
                 specified by the password database entry of the target user
                 as a login shell.  This means that login-specific resource
                 files such as .profile or .login will be read by the shell.
                 If a command is specified, it is passed to the shell for
                 execution via the shell's -c option.  If no command is
                 specified, an interactive shell is executed.  sudo attempts
                 to change to that user's home directory before running the
                 shell.  The security policy shall initialize the environment
                 to a minimal set of variables, similar to what is present
                 when a user logs in.  The Command Environment section in the
                 sudoers(4) manual documents how the -i option affects the
                 environment in which a command is run when the sudoers policy
                 is in use.

     -K          The -K (sure kill) option is like -k except that it removes
                 the user's cached credentials entirely and may not be used in
                 conjunction with a command or other option.  This option does
                 not require a password.  Not all security policies support
                 credential caching.

     -k [command]
                 When used alone, the -k (kill) option to sudo invalidates the
                 user's cached credentials.  The next time sudo is run a
                 password will be required.  This option does not require a
                 password and was added to allow a user to revoke sudo
                 permissions from a .logout file.  Not all security policies
                 support credential caching.

                 When used in conjunction with a command or an option that may
                 require a password, the -k option will cause sudo to ignore
                 the user's cached credentials.  As a result, sudo will prompt
                 for a password (if one is required by the security policy)
                 and will not update the user's cached credentials.

     -l[ll] [command]
                 If no command is specified, the -l (list) option will list
                 the allowed (and forbidden) commands for the invoking user
                 (or the user specified by the -U option) on the current host.
                 If a command is specified and is permitted by the security
                 policy, the fully-qualified path to the command is displayed
                 along with any command line arguments.  If command is
                 specified but not allowed, sudo will exit with a status value
                 of 1.  If the -l option is specified with an _l argument (i.e.
                 -ll), or if -l is specified multiple times, a longer list
                 format is used.

     -n          The -n (non-interactive) option prevents sudo from prompting
                 the user for a password.  If a password is required for the
                 command to run, sudo will display an error message and exit.

     -P          The -P (preserve group vector) option causes sudo to preserve
                 the invoking user's group vector unaltered.  By default, the
                 sudoers policy will initialize the group vector to the list
                 of groups the target user is in.  The real and effective
                 group IDs, however, are still set to match the target user.

     -p prompt   The -p (prompt) option allows you to override the default
                 password prompt and use a custom one.  The following percent
                 (`%') escapes are supported by the sudoers policy:

                 %H  expanded to the host name including the domain name (on
                     if the machine's host name is fully qualified or the fqdn
                     option is set in sudoers(4))

                 %h  expanded to the local host name without the domain name

                 %p  expanded to the name of the user whose password is being
                     requested (respects the rootpw, targetpw, and runaspw
                     flags in sudoers(4))

                 %U  expanded to the login name of the user the command will
                     be run as (defaults to root unless the -u option is also
                     specified)

                 %u  expanded to the invoking user's login name

                 %%  two consecutive `%' characters are collapsed into a
                     single `%' character

                 The prompt specified by the -p option will override the
                 system password prompt on systems that support PAM unless the
                 passprompt__override flag is disabled in sudoers.

     -r role     The -r (role) option causes the new (SELinux) security
                 context to have the role specified by role.

     -S          The -S (stdin) option causes sudo to read the password from
                 the standard input instead of the terminal device.  The
                 password must be followed by a newline character.

     -s [command]
                 The -s (shell) option runs the shell specified by the SHELL
                 environment variable if it is set or the shell as specified
                 in the password database.  If a command is specified, it is
                 passed to the shell for execution via the shell's -c option.
                 If no command is specified, an interactive shell is executed.

     -t type     The -t (type) option causes the new (SELinux) security
                 context to have the type specified by type.  If no type is
                 specified, the default type is derived from the specified
                 role.

     -U user     The -U (other user) option is used in conjunction with the -l
                 option to specify the user whose privileges should be listed.
                 The security policy may restrict listing other users'
                 privileges.  The sudoers policy only allows root or a user
                 with the ALL privilege on the current host to use this
                 option.

     -u user     The -u (user) option causes sudo to run the specified command
                 as a user other than root.  To specify a uid instead of a
                 user name, #uid.  When running commands as a uid, many shells
                 require that the `#' be escaped with a backslash (`\').
                 Security policies may restrict uids to those listed in the
                 password database.  The sudoers policy allows uids that are
                 not in the password database as long as the targetpw option
                 is not set.  Other security policies may not support this.

     -V          The -V (version) option causes sudo to print its version
                 string and the version string of the security policy plugin
                 and any I/O plugins.  If the invoking user is already root
                 the -V option will display the arguments passed to configure
                 when sudo was built and plugins may display more verbose
                 information such as default options.

     -v          When given the -v (validate) option, sudo will update the
                 user's cached credentials, authenticating the user's password
                 if necessary.  For the sudoers plugin, this extends the sudo
                 timeout for another 5 minutes (or whatever the timeout is set
                 to by the security policy) but does not run a command.  Not
                 all security policies support cached credentials.

     ----          The ---- option indicates that sudo should stop processing
                 command line arguments.

     Environment variables to be set for the command may also be passed on the
     command line in the form of VAR=value, e.g.
     LD_LIBRARY_PATH=/usr/local/pkg/lib.  Variables passed on the command line
     are subject to the same restrictions as normal environment variables with
     one important exception.  If the setenv option is set in sudoers, the
     command to be run has the SETENV tag set or the command matched is ALL,
     the user may set variables that would otherwise be forbidden.  See
     sudoers(4) for more information.

COMMAND EXECUTION
     When sudo executes a command, the security policy specifies the execution
     envionment for the command.  Typically, the real and effective uid and
     gid are set to match those of the target user, as specified in the
     password database, and the group vector is initialized based on the group
     database (unless the -P option was specified).

     The following parameters may be specified by security policy:

     oo   real and effective user ID

     oo   real and effective group ID

     oo   supplementary group IDs

     oo   the environment list

     oo   current working directory

     oo   file creation mode mask (umask)

     oo   SELinux role and type

     oo   Solaris project

     oo   Solaris privileges

     oo   BSD login class

     oo   scheduling priority (aka nice value)

   Process model
     When sudo runs a command, it calls fork(2), sets up the execution
     environment as described above, and calls the execve system call in the
     child process.  The main sudo process waits until the command has
     completed, then passes the command's exit status to the security policy's
     close method and exits.  If an I/O logging plugin is configured, a new
     pseudo-terminal (``pty'') is created and a second sudo process is used to
     relay job control signals between the user's existing pty and the new pty
     the command is being run in.  This extra process makes it possible to,
     for example, suspend and resume the command.  Without it, the command
     would be in what POSIX terms an ``orphaned process group'' and it would
     not receive any job control signals.

   Signal handling
     Because the command is run as a child of the sudo process, sudo will
     relay signals it receives to the command.  Unless the command is being
     run in a new pty, the SIGHUP, SIGINT and SIGQUIT signals are not relayed
     unless they are sent by a user process, not the kernel.  Otherwise, the
     command would receive SIGINT twice every time the user entered control-C.
     Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will
     not be relayed to the command.  As a general rule, SIGTSTP should be used
     instead of SIGSTOP when you wish to suspend a command being run by sudo.

     As a special case, sudo will not relay signals that were sent by the
     command it is running.  This prevents the command from accidentally
     killing itself.  On some systems, the reboot(1m) command sends SIGTERM to
     all non-system processes other than itself before rebooting the systyem.
     This prevents sudo from relaying the SIGTERM signal it received back to
     reboot(1m), which might then exit before the system was actually rebooted,
     leaving it in a half-dead state similar to single user mode.  Note,
     however, that this check only applies to the command run by sudo and not
     any other processes that the command may create.  As a result, running a
     script that calls reboot(1m) or shutdown(1m) via sudo may cause the system
     to end up in this undefined state unless the reboot(1m) or shutdown(1m) are
     run using the exec() family of functions instead of system() (which
     interposes a shell between the command and the calling process).

PLUGINS
     Plugins are dynamically loaded based on the contents of the
     /etc/sudo.conf file.  If no /etc/sudo.conf file is present, or it
     contains no Plugin lines, sudo will use the traditional sudoers security
     policy and I/O logging, which corresponds to the following /etc/sudo.conf
     file.

     #
     # Default /etc/sudo.conf file
     #
     # Format:
     #   Plugin plugin_name plugin_path plugin_options ...
     #   Path askpass /path/to/askpass
     #   Path noexec /path/to/sudo_noexec.so
     #   Debug sudo /var/log/sudo_debug all@warn
     #   Set disable_coredump true
     #
     # The plugin_path is relative to /usr/local/libexec unless
     #   fully qualified.
     # The plugin_name corresponds to a global symbol in the plugin
     #   that contains the plugin interface structure.
     # The plugin_options are optional.
     #
     Plugin policy_plugin sudoers.so
     Plugin io_plugin sudoers.so

     A Plugin line consists of the Plugin keyword, followed by the symbol__name
     and the path to the shared object containing the plugin.  The symbol__name
     is the name of the struct policy_plugin or struct io_plugin in the plugin
     shared object.  The path may be fully qualified or relative.  If not
     fully qualified it is relative to the /usr/local/libexec directory.  Any
     additional parameters after the path are passed as arguments to the
     plugin's open function.  Lines that don't begin with Plugin, Path, Debug,
     or Set are silently ignored.

     For more information, see the sudo_plugin(1m) manual.

PATHS
     A Path line consists of the Path keyword, followed by the name of the
     path to set and its value.  E.g.

           Path noexec /usr/local/libexec/sudo_noexec.so
           Path askpass /usr/X11R6/bin/ssh-askpass

     The following plugin-agnostic paths may be set in the /etc/sudo.conf
     file:

     askpass   The fully qualified path to a helper program used to read the
               user's password when no terminal is available.  This may be the
               case when sudo is executed from a graphical (as opposed to
               text-based) application.  The program specified by askpass
               should display the argument passed to it as the prompt and
               write the user's password to the standard output.  The value of
               askpass may be overridden by the SUDO_ASKPASS environment
               variable.

     noexec    The fully-qualified path to a shared library containing dummy
               versions of the execv(), execve() and fexecve() library
               functions that just return an error.  This is used to implement
               the noexec functionality on systems that support LD_PRELOAD or
               its equivalent.  Defaults to /usr/local/libexec/sudo__noexec.so.

DEBUG FLAGS
     sudo versions 1.8.4 and higher support a flexible debugging framework
     that can help track down what sudo is doing internally if there is a
     problem.

     A Debug line consists of the Debug keyword, followed by the name of the
     program to debug (sudo, visudo, sudoreplay), the debug file name and a
     comma-separated list of debug flags.  The debug flag syntax used by sudo
     and the sudoers plugin is subsystem@priority but the plugin is free to
     use a different format so long as it does not include a comma (`,').

     For instance:

           Debug sudo /var/log/sudo_debug all@warn,plugin@info

     would log all debugging statements at the warn level and higher in
     addition to those at the info level for the plugin subsystem.

     Currently, only one Debug entry per program is supported.  The sudo Debug
     entry is shared by the sudo front end, sudoedit and the plugins.  A
     future release may add support for per-plugin Debug lines and/or support
     for multiple debugging files for a single program.

     The priorities used by the sudo front end, in order of decreasing
     severity, are: crit, err, warn, notice, diag, info, trace and debug.
     Each priority, when specified, also includes all priorities higher than
     it.  For example, a priority of notice would include debug messages
     logged at notice and higher.

     The following subsystems are used by the sudo front-end:

     all         matches every subsystem

     args        command line argument processing

     conv        user conversation

     edit        sudoedit

     exec        command execution

     main        sudo main function

     netif       network interface handling

     pcomm       communication with the plugin

     plugin      plugin configuration

     pty         pseudo-tty related code

     selinux     SELinux-specific handling

     util        utility functions

     utmp        utmp handling

EXIT VALUE
     Upon successful execution of a program, the exit status from sudo will
     simply be the exit status of the program that was executed.

     Otherwise, sudo exits with a value of 1 if there is a
     configuration/permission problem or if sudo cannot execute the given
     command.  In the latter case the error string is printed to the standard
     error.  If sudo cannot stat(2) one or more entries in the user's PATH, an
     error is printed on stderr.  (If the directory does not exist or if it is
     not really a directory, the entry is ignored and no error is printed.)
     This should not happen under normal circumstances.  The most common
     reason for stat(2) to return ``permission denied'' is if you are running
     an automounter and one of the directories in your PATH is on a machine
     that is currently unreachable.

SECURITY NOTES
     sudo tries to be safe when executing external commands.

     To prevent command spoofing, sudo checks "." and "" (both denoting
     current directory) last when searching for a command in the user's PATH
     (if one or both are in the PATH).  Note, however, that the actual PATH
     environment variable is not modified and is passed unchanged to the
     program that sudo executes.

     Please note that sudo will normally only log the command it explicitly
     runs.  If a user runs a command such as sudo su or sudo sh, subsequent
     commands run from that shell are not subject to sudo's security policy.
     The same is true for commands that offer shell escapes (including most
     editors).  If I/O logging is enabled, subsequent commands will have their
     input and/or output logged, but there will not be traditional logs for
     those commands.  Because of this, care must be taken when giving users
     access to commands via sudo to verify that the command does not
     inadvertently give the user an effective root shell.  For more
     information, please see the PREVENTING SHELL ESCAPES section in
     sudoers(4).

     To prevent the disclosure of potentially sensitive information, sudo
     disables core dumps by default while it is executing (they are re-enabled
     for the command that is run).  To aid in debugging sudo crashes, you may
     wish to re-enable core dumps by setting ``disable_coredump'' to false in
     the /etc/sudo.conf file as follows:

           Set disable_coredump false

     Note that by default, most operating systems disable core dumps from
     setuid programs, which includes sudo.  To actually get a sudo core file
     you may need to enable core dumps for setuid processes.  On BSD and Linux
     systems this is accomplished via the sysctl command, on Solaris the
     coreadm command can be used.

ENVIRONMENT
     sudo utilizes the following environment variables.  The security policy
     has control over the actual content of the command's environment.

     EDITOR           Default editor to use in -e (sudoedit) mode if neither
                      SUDO_EDITOR nor VISUAL is set.

     MAIL             In -i mode or when env__reset is enabled in sudoers, set
                      to the mail spool of the target user.

     HOME             Set to the home directory of the target user if -i or -H
                      are specified, env__reset or always__set__home are set in
                      sudoers, or when the -s option is specified and set__home
                      is set in sudoers.

     PATH             May be overridden by the security policy.

     SHELL            Used to determine shell to run with -s option.

     SUDO_ASKPASS     Specifies the path to a helper program used to read the
                      password if no terminal is available or if the -A option
                      is specified.

     SUDO_COMMAND     Set to the command run by sudo.

     SUDO_EDITOR      Default editor to use in -e (sudoedit) mode.

     SUDO_GID         Set to the group ID of the user who invoked sudo.

     SUDO_PROMPT      Used as the default password prompt.

     SUDO_PS1         If set, PS1 will be set to its value for the program
                      being run.

     SUDO_UID         Set to the user ID of the user who invoked sudo.

     SUDO_USER        Set to the login name of the user who invoked sudo.

     USER             Set to the target user (root unless the -u option is
                      specified).

     VISUAL           Default editor to use in -e (sudoedit) mode if
                      SUDO_EDITOR is not set.

FILES
     /etc/sudo.conf            sudo front end configuration

EXAMPLES
     Note: the following examples assume a properly configured security
     policy.

     To get a file listing of an unreadable directory:

           $ sudo ls /usr/local/protected

     To list the home directory of user yaz on a machine where the file system
     holding ~yaz is not exported as root:

           $ sudo -u yaz ls ~yaz

     To edit the index.html file as user www:

           $ sudo -u www vi ~www/htdocs/index.html

     To view system logs only accessible to root and users in the adm group:

           $ sudo -g adm view /var/log/syslog

     To run an editor as jim with a different primary group:

           $ sudo -u jim -g audio vi ~jim/sound.txt

     To shut down a machine:

           $ sudo shutdown -r +15 "quick reboot"

     To make a usage listing of the directories in the /home partition.  Note
     that this runs the commands in a sub-shell to make the cd and file
     redirection work.

           $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"

SEE ALSO
     grep(1), su(1), stat(2), login_cap(3), passwd(4), sudoers(4),
     sudo_plugin(1m), sudoreplay(1m), visudo(1m)

HISTORY
     See the HISTORY file in the sudo distribution
     (http://www.sudo.ws/sudo/history.html) for a brief history of sudo.

AUTHORS
     Many people have worked on sudo over the years; this version consists of
     code written primarily by:

           Todd C. Miller

     See the CONTRIBUTORS file in the sudo distribution
     (http://www.sudo.ws/sudo/contributors.html) for an exhaustive list of
     people who have contributed to sudo.

CAVEATS
     There is no easy way to prevent a user from gaining a root shell if that
     user is allowed to run arbitrary commands via sudo.  Also, many programs
     (such as editors) allow the user to run commands via shell escapes, thus
     avoiding sudo's checks.  However, on most systems it is possible to
     prevent shell escapes with the sudoers(4) plugin's noexec functionality.

     It is not meaningful to run the cd command directly via sudo, e.g.,

           $ sudo cd /usr/local/protected

     since when the command exits the parent process (your shell) will still
     be the same.  Please see the EXAMPLES section for more information.

     Running shell scripts via sudo can expose the same kernel bugs that make
     setuid shell scripts unsafe on some operating systems (if your OS has a
     /dev/fd/ directory, setuid shell scripts are generally safe).

BUGS
     If you feel you have found a bug in sudo, please submit a bug report at
     http://www.sudo.ws/sudo/bugs/

SUPPORT
     Limited free support is available via the sudo-users mailing list, see
     http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the
     archives.

DISCLAIMER
     sudo is provided ``AS IS'' and any express or implied warranties,
     including, but not limited to, the implied warranties of merchantability
     and fitness for a particular purpose are disclaimed.  See the LICENSE
     file distributed with sudo or http://www.sudo.ws/sudo/license.html for
     complete details.

Sudo 1.8.6                       July 10, 2012                      Sudo 1.8.6
