MirBSD manpage: sudoers(5)



     sudoers - list of which users may execute what


     The sudoers file is composed of two types of entries:
     aliases (basically variables) and user specifications (which
     specify who may run what).

     When multiple entries match for a user, they are applied in
     order. Where there are conflicting values, the last match is
     used (which is not necessarily the most specific match).

     The sudoers grammar will be described below in Extended
     Backus-Naur Form (EBNF).  Don't despair if you don't know
     what EBNF is; it is fairly simple, and the definitions below
     are annotated.

     Quick guide to EBNF

     EBNF is a concise and exact way of describing the grammar of
     a language. Each EBNF definition is made up of production
     rules.  E.g.,

      symbol ::= definition | alternate1 | alternate2 ...

     Each production rule references others and thus makes up a
     grammar for the language.  EBNF also contains the following
     operators, which many readers will recognize from regular
     expressions.  Do not, however, confuse them with "wildcard"
     characters, which have different meanings.

     ?       Means that the preceding symbol (or group of sym-
             bols) is optional. That is, it may appear once or
             not at all.

     *       Means that the preceding symbol (or group of sym-
             bols) may appear zero or more times.

     +       Means that the preceding symbol (or group of sym-
             bols) may appear one or more times.

     Parentheses may be used to group symbols together.  For
     clarity, we will use single quotes ('') to designate what is
     a verbatim character string (as opposed to a symbol name).


     There are four kinds of aliases: User_Alias, Runas_Alias,
     Host_Alias and Cmnd_Alias.

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      Alias ::= 'User_Alias'  User_Alias (':' User_Alias)* |
                'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
                'Host_Alias'  Host_Alias (':' Host_Alias)* |
                'Cmnd_Alias'  Cmnd_Alias (':' Cmnd_Alias)*

      User_Alias ::= NAME '=' User_List

      Runas_Alias ::= NAME '=' Runas_List

      Host_Alias ::= NAME '=' Host_List

      Cmnd_Alias ::= NAME '=' Cmnd_List

      NAME ::= [A-Z]([A-Z][0-9]_)*

     Each alias definition is of the form

      Alias_Type NAME = item1, item2, ...

     where Alias_Type is one of User_Alias, Runas_Alias,
     Host_Alias, or Cmnd_Alias.  A NAME is a string of uppercase
     letters, numbers, and underscore characters ('_').  A NAME
     must start with an uppercase letter.  It is possible to put
     several alias definitions of the same type on a single line,
     joined by a colon (':').  E.g.,

      Alias_Type NAME = item1, item2, item3 : NAME = item4, item5

     The definitions of what constitutes a valid alias member

      User_List ::= User |
                    User ',' User_List

      User ::= '!'* username |
               '!'* '%'group |
               '!'* '+'netgroup |
               '!'* User_Alias

     A User_List is made up of one or more usernames, system
     groups (prefixed with '%'), netgroups (prefixed with '+')
     and other aliases. Each list item may be prefixed with one
     or more '!' operators. An odd number of '!' operators negate
     the value of the item; an even number just cancel each other

      Runas_List ::= Runas_User |
                     Runas_User ',' Runas_List

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      Runas_User ::= '!'* username |
                     '!'* '#'uid |
                     '!'* '%'group |
                     '!'* +netgroup |
                     '!'* Runas_Alias

     A Runas_List is similar to a User_List except that it can
     also contain uids (prefixed with '#') and instead of
     User_Aliases it can contain Runas_Aliases.  Note that user-
     names and groups are matched as strings.  In other words,
     two users (groups) with the same uid (gid) are considered to
     be distinct.  If you wish to match all usernames with the
     same uid (e.g. root and toor), you can use a uid instead (#0
     in the example given).

      Host_List ::= Host |
                    Host ',' Host_List

      Host ::= '!'* hostname |
               '!'* ip_addr |
               '!'* network(/netmask)? |
               '!'* '+'netgroup |
               '!'* Host_Alias

     A Host_List is made up of one or more hostnames, IP
     addresses, network numbers, netgroups (prefixed with '+')
     and other aliases. Again, the value of an item may be
     negated with the '!' operator. If you do not specify a net-
     mask with a network number, the netmask of the host's ether-
     net interface(s) will be used when matching. The netmask may
     be specified either in dotted quad notation (e.g. or CIDR notation (number of bits, e.g. 24).
     A hostname may include shell-style wildcards (see the Wild-
     cards section below), but unless the hostname command on
     your machine returns the fully qualified hostname, you'll
     need to use the fqdn option for wildcards to be useful.

      Cmnd_List ::= Cmnd |
                    Cmnd ',' Cmnd_List

      commandname ::= filename |
                      filename args |
                      filename '""'

      Cmnd ::= '!'* commandname |
               '!'* directory |
               '!'* "sudoedit" |
               '!'* Cmnd_Alias

     A Cmnd_List is a list of one or more commandnames, direc-
     tories, and other aliases.  A commandname is a fully quali-
     fied filename which may include shell-style wildcards (see

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     the Wildcards section below).  A simple filename allows the
     user to run the command with any arguments he/she wishes.
     However, you may also specify command line arguments
     (including wildcards).  Alternately, you can specify "" to
     indicate that the command may only be run without command
     line arguments.  A directory is a fully qualified pathname
     ending in a '/'.  When you specify a directory in a
     Cmnd_List, the user will be able to run any file within that
     directory (but not in any subdirectories therein).

     If a Cmnd has associated command line arguments, then the
     arguments in the Cmnd must match exactly those given by the
     user on the command line (or match the wildcards if there
     are any).  Note that the following characters must be
     escaped with a '\' if they are used in command arguments:
     ',', ':', '=', '\'.  The special command "sudoedit" is used
     to permit a user to run sudo with the -e flag (or as
     sudoedit).  It may take command line arguments just as a
     normal command does.


     Certain configuration options may be changed from their
     default values at runtime via one or more Default_Entry
     lines.  These may affect all users on any host, all users on
     a specific host, a specific user, or commands being run as a
     specific user.

      Default_Type ::= 'Defaults' |
                       'Defaults' '@' Host |
                       'Defaults' ':' User |
                       'Defaults' '>' RunasUser

      Default_Entry ::= Default_Type Parameter_List

      Parameter_List ::= Parameter |
                         Parameter ',' Parameter_List

      Parameter ::= Parameter '=' Value |
                    Parameter '+=' Value |
                    Parameter '-=' Value |
                    '!'* Parameter

     Parameters may be flags, integer values, strings, or lists.
     Flags are implicitly boolean and can be turned off via the
     '!' operator.  Some integer, string and list parameters may
     also be used in a boolean context to disable them.  Values
     may be enclosed in double quotes (") when they contain mul-
     tiple words.  Special characters may be escaped with a
     backslash (\).

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     Lists have two additional assignment operators, += and -=.
     These operators are used to add to and delete from a list
     respectively. It is not an error to use the -= operator to
     remove an element that does not exist in a list.


                 When validating with a One Time Password scheme
                 (S/Key or OPIE), a two-line prompt is used to
                 make it easier to cut and paste the challenge to
                 a local window.  It's not as pretty as the
                 default but some people find it more convenient.
                 This flag is off by default.

     ignore_dot  If set, sudo will ignore '.' or '' (current dir)
                 in the PATH environment variable; the PATH
                 itself is not modified.  This flag is off by
                 default.  Currently, while it is possible to set
                 ignore_dot in sudoers, its value is not used.
                 This option should be considered read-only (it
                 will be fixed in a future version of sudo).

     mail_always Send mail to the mailto user every time a users
                 runs sudo. This flag is off by default.

                 Send mail to the mailto user if the user running
                 sudo does not enter the correct password.  This
                 flag is off by default.

                 If set, mail will be sent to the mailto user if
                 the invoking user is not in the sudoers file.
                 This flag is on by default.

                 If set, mail will be sent to the mailto user if
                 the invoking user exists in the sudoers file,
                 but is not allowed to run commands on the
                 current host.  This flag is off by default.

                 If set, mail will be sent to the mailto user if
                 the invoking user is allowed to use sudo but the
                 command they are trying is not listed in their
                 sudoers file entry or is explicitly denied. This
                 flag is off by default.

     tty_tickets If set, users must authenticate on a per-tty
                 basis.  Normally, sudo uses a directory in the
                 ticket dir with the same name as the user

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                 running it.  With this flag enabled, sudo will
                 use a file named for the tty the user is logged
                 in on in that directory. This flag is off by

                 If set, users must authenticate themselves via a
                 password (or other means of authentication)
                 before they may run commands.  This default may
                 be overridden via the PASSWD and NOPASSWD tags.
                 This flag is on by default.

     root_sudo   If set, root is allowed to run sudo too.  Disa-
                 bling this prevents users from "chaining" sudo
                 commands to get a root shell by doing something
                 like "sudo sudo /bin/sh".  Note, however, that
                 turning off root_sudo will also prevent root and
                 from running sudoedit. Disabling root_sudo pro-
                 vides no real additional security; it exists
                 purely for historical reasons. This flag is on
                 by default.

     log_host    If set, the hostname will be logged in the
                 (non-syslog) sudo log file. This flag is off by

     log_year    If set, the four-digit year will be logged in
                 the (non-syslog) sudo log file. This flag is off
                 by default.

                 If set and sudo is invoked with no arguments it
                 acts as if the -s flag had been given.  That is,
                 it runs a shell as root (the shell is determined
                 by the SHELL environment variable if it is set,
                 falling back on the shell listed in the invoking
                 user's /etc/passwd entry if not).  This flag is
                 off by default.

     set_home    If set and sudo is invoked with the -s flag the
                 HOME environment variable will be set to the
                 home directory of the target user (which is root
                 unless the -u option is used).  This effectively
                 makes the -s flag imply -H.  This flag is off by

                 If set, sudo will set the HOME environment vari-
                 able to the home directory of the target user
                 (which is root unless the -u option is used).
                 This effectively means that the -H flag is
                 always implied. This flag is off by default.

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     path_info   Normally, sudo will tell the user when a command
                 could not be found in their PATH environment
                 variable.  Some sites may wish to disable this
                 as it could be used to gather information on the
                 location of executables that the normal user
                 does not have access to.  The disadvantage is
                 that if the executable is simply not in the
                 user's PATH, sudo will tell the user that they
                 are not allowed to run it, which can be confus-
                 ing.  This flag is off by default.

                 By default sudo will initialize the group vector
                 to the list of groups the target user is in.
                 When preserve_groups is set, the user's existing
                 group vector is left unaltered.  The real and
                 effective group IDs, however, are still set to
                 match the target user.  This flag is off by

     fqdn        Set this flag if you want to put fully qualified
                 hostnames in the sudoers file.  I.e., instead of
                 myhost you would use myhost.mydomain.edu. You
                 may still use the short form if you wish (and
                 even mix the two). Beware that turning on fqdn
                 requires sudo to make DNS lookups which may make
                 sudo unusable if DNS stops working (for example
                 if the machine is not plugged into the network).
                 Also note that you must use the host's official
                 name as DNS knows it.  That is, you may not use
                 a host alias (CNAME entry) due to performance
                 issues and the fact that there is no way to get
                 all aliases from DNS.  If your machine's host-
                 name (as returned by the hostname command) is
                 already fully qualified you shouldn't need to
                 set fqdn.  This flag is off by default.

     insults     If set, sudo will insult users when they enter
                 an incorrect password.  This flag is on by

     requiretty  If set, sudo will only run when the user is
                 logged in to a real tty.  This will disallow
                 things like "rsh somehost sudo ls" since rsh(1)
                 does not allocate a tty.  Because it is not pos-
                 sible to turn off echo when there is no tty
                 present, some sites may with to set this flag to
                 prevent a user from entering a visible password.
                 This flag is off by default.

     env_editor  If set, visudo will use the value of the EDITOR
                 or VISUAL environment variables before falling

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                 back on the default editor list. Note that this
                 may create a security hole as it allows the user
                 to run any arbitrary command as root without
                 logging.  A safer alternative is to place a
                 colon-separated list of editors in the editor
                 variable.  visudo will then only use the EDITOR
                 or VISUAL if they match a value specified in
                 editor.  This flag is on by default.

     rootpw      If set, sudo will prompt for the root password
                 instead of the password of the invoking user.
                 This flag is off by default.

     runaspw     If set, sudo will prompt for the password of the
                 user defined by the runas_default option
                 (defaults to root) instead of the password of
                 the invoking user.  This flag is off by default.

     targetpw    If set, sudo will prompt for the password of the
                 user specified by the -u flag (defaults to root)
                 instead of the password of the invoking user.
                 Note that this precludes the use of a uid not
                 listed in the passwd database as an argument to
                 the -u flag. This flag is off by default.

     set_logname Normally, sudo will set the LOGNAME and USER
                 environment variables to the name of the target
                 user (usually root unless the -u flag is given).
                 However, since some programs (including the RCS
                 revision control system) use LOGNAME to deter-
                 mine the real identity of the user, it may be
                 desirable to change this behavior.  This can be
                 done by negating the set_logname option.

     stay_setuid Normally, when sudo executes a command the real
                 and effective UIDs are set to the target user
                 (root by default).  This option changes that
                 behavior such that the real UID is left as the
                 invoking user's UID.  In other words, this makes
                 sudo act as a setuid wrapper.  This can be use-
                 ful on systems that disable some potentially
                 dangerous functionality when a program is run
                 setuid.  Note, however, that this means that
                 sudo will run with the real uid of the invoking
                 user which may allow that user to kill sudo
                 before it can log a failure, depending on how
                 your OS defines the interaction between signals
                 and setuid processes.

     env_reset   If set, sudo will reset the environment to only
                 contain the following variables: HOME, LOGNAME,
                 PATH, SHELL, TERM, and USER (in addition to the

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                 SUDO_* variables). Of these, only TERM is copied
                 unaltered from the old environment. The other
                 variables are set to default values (possibly
                 modified by the value of the set_logname
                 option).  If sudo was compiled with the
                 SECURE_PATH option, its value will be used for
                 the PATH environment variable. Other variables
                 may be preserved with the env_keep option.

                 If set, sudo will apply the defaults specified
                 for the target user's login class if one exists.
                 Only available if sudo is configured with the
                 --with-logincap option.  This flag is off by

     noexec      If set, all commands run via sudo will behave as
                 if the NOEXEC tag has been set, unless overrid-
                 den by a EXEC tag.  See the description of
                 NOEXEC and EXEC below as well as the "PREVENTING
                 SHELL ESCAPES" section at the end of this
                 manual.  This flag is off by default.

                 If set via LDAP, parsing of @sysconfdir@/sudoers
                 will be skipped. This is intended for an Enter-
                 prises that wish to prevent the usage of local
                 sudoers files so that only LDAP is used.  This
                 thwarts the efforts of rogue operators who would
                 attempt to add roles to @sysconfdir@/sudoers.
                 When this option is present,
                 @sysconfdir@/sudoers does not even need to
                 exist. Since this options tells sudo how to
                 behave when no specific LDAP entries have been
                 matched, this sudoOption is only meaningful for
                 the cn=defaults section.  This flag is off by


                 The number of tries a user gets to enter his/her
                 password before sudo logs the failure and exits.
                 The default is 3.

     Integers that can be used in a boolean context:

     loglinelen  Number of characters per line for the file log.
                 This value is used to decide when to wrap lines
                 for nicer log files.  This has no effect on the
                 syslog log file, only the file log.  The default
                 is 80 (use 0 or negate the option to disable

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                 word wrap).

                 Number of minutes that can elapse before sudo
                 will ask for a passwd again.  The default is 5.
                 Set this to 0 to always prompt for a password.
                 If set to a value less than 0 the user's times-
                 tamp will never expire.  This can be used to
                 allow users to create or delete their own times-
                 tamps via sudo -v and sudo -k respectively.

                 Number of minutes before the sudo password
                 prompt times out. The default is 5, set this to
                 0 for no password timeout.

     umask       Umask to use when running the command.  Negate
                 this option or set it to 0777 to preserve the
                 user's umask.  The default is 0022.


     mailsub     Subject of the mail sent to the mailto user. The
                 escape %h will expand to the hostname of the
                 machine. Default is *** SECURITY information for
                 %h ***.

                 Message that is displayed if a user enters an
                 incorrect password. The default is Sorry, try
                 again. unless insults are enabled.

                 The directory in which sudo stores its timestamp
                 files. The default is /var/run/sudo.

                 The owner of the timestamp directory and the
                 timestamps stored therein. The default is root.

     passprompt  The default prompt to use when asking for a
                 password; can be overridden via the -p option or
                 the SUDO_PROMPT environment variable. The fol-
                 lowing percent (`%') escapes are supported:

                 %u      expanded to the invoking user's login

                 %U      expanded to the login name of the user
                         the command will be run as (defaults to

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                 %h      expanded to the local hostname without
                         the domain name

                 %H      expanded to the local hostname including
                         the domain name (on if the machine's
                         hostname is fully qualified or the fqdn
                         option is set)

                 %%      two consecutive % characters are col-
                         laped into a single % character

                 The default value is Password:.

                 The default user to run commands as if the -u
                 flag is not specified on the command line.  This
                 defaults to root. Note that if runas_default is
                 set it must occur before any Runas_Alias specif-

                 Syslog priority to use when user authenticates
                 successfully. Defaults to notice.

                 Syslog priority to use when user authenticates
                 unsuccessfully. Defaults to alert.

     editor      A colon (':') separated list of editors allowed
                 to be used with visudo.  visudo will choose the
                 editor that matches the user's USER environment
                 variable if possible, or the first editor in the
                 list that exists and is executable.  The default
                 is the path to vi on your system.

     noexec_file Path to a shared library containing dummy ver-
                 sions of the execv(), execve() and fexecve()
                 library functions that just return an error.
                 This is used to implement the noexec functional-
                 ity on systems that support LD_PRELOAD or its
                 equivalent.  Defaults to

     Strings that can be used in a boolean context:

     lecture     This option controls when a short lecture will
                 be printed along with the password prompt.  It
                 has the following possible values:

                 never   Never lecture the user.

                 once    Only lecture the user the first time

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                         they run sudo.

                 always  Always lecture the user.

                 If no value is specified, a value of once is
                 implied. Negating the option results in a value
                 of never being used. The default value is once.

                 Path to a file containing an alternate sudo lec-
                 ture that will be used in place of the standard
                 lecture if the named file exists.

     logfile     Path to the sudo log file (not the syslog log
                 file).  Setting a path turns on logging to a
                 file; negating this option turns it off.

     syslog      Syslog facility if syslog is being used for log-
                 ging (negate to disable syslog logging).
                 Defaults to authpriv.

     mailerpath  Path to mail program used to send warning mail.
                 Defaults to the path to sendmail found at con-
                 figure time.

     mailerflags Flags to use when invoking mailer. Defaults to

     mailto      Address to send warning and error mail to.  The
                 address should be enclosed in double quotes (")
                 to protect against sudo interpreting the @ sign.
                 Defaults to root.

                 Users in this group are exempt from password and
                 PATH requirements. This is not set by default.

     verifypw    This option controls when a password will be
                 required when a user runs sudo with the -v flag.
                 It has the following possible values:

                 all     All the user's sudoers entries for the
                         current host must have the NOPASSWD flag
                         set to avoid entering a password.

                 any     At least one of the user's sudoers
                         entries for the current host must have
                         the NOPASSWD flag set to avoid entering
                         a password.

                 never   The user need never enter a password to
                         use the -v flag.

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                 always  The user must always enter a password to
                         use the -v flag.

                 If no value is specified, a value of all is
                 implied. Negating the option results in a value
                 of never being used. The default value is all.

     listpw      This option controls when a password will be
                 required when a user runs sudo with the -l flag.
                 It has the following possible values:

                 all     All the user's sudoers entries for the
                         current host must have the NOPASSWD flag
                         set to avoid entering a password.

                 any     At least one of the user's sudoers
                         entries for the current host must have
                         the NOPASSWD flag set to avoid entering
                         a password.

                 never   The user need never enter a password to
                         use the -l flag.

                 always  The user must always enter a password to
                         use the -l flag.

                 If no value is specified, a value of any is
                 implied. Negating the option results in a value
                 of never being used. The default value is any.

     Lists that can be used in a boolean context:

     env_check   Environment variables to be removed from the
                 user's environment if the variable's value con-
                 tains % or / characters.  This can be used to
                 guard against printf-style format vulnerabili-
                 ties in poorly-written programs.  The argument
                 may be a double-quoted, space-separated list or
                 a single value without double-quotes.  The list
                 can be replaced, added to, deleted from, or dis-
                 abled by using the =, +=, -=, and ! operators
                 respectively.  The default list of environment
                 variables to check is printed when sudo is run
                 by root with the -V option.

     env_delete  Environment variables to be removed from the
                 user's environment. The argument may be a
                 double-quoted, space-separated list or a single
                 value without double-quotes.  The list can be
                 replaced, added to, deleted from, or disabled by
                 using the =, +=, -=, and ! operators respec-
                 tively.  The default list of environment

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                 variables to remove is printed when sudo is run
                 by root with the -V option.  Note that many
                 operating systems will remove potentially
                 dangerous variables from the environment of any
                 setuid process (such as sudo).

     env_keep    Environment variables to be preserved in the
                 user's environment when the env_reset option is
                 in effect.  This allows fine-grained control
                 over the environment sudo-spawned processes will
                 receive. The argument may be a double-quoted,
                 space-separated list or a single value without
                 double-quotes.  The list can be replaced, added
                 to, deleted from, or disabled by using the =,
                 +=, -=, and ! operators respectively.  This list
                 has no default members.

     When logging via syslog(3), sudo accepts the following
     values for the syslog facility (the value of the syslog
     Parameter): authpriv (if your OS supports it), auth, daemon,
     user, local0, local1, local2, local3, local4, local5,
     local6, and local7.  The following syslog priorities are
     supported: alert, crit, debug, emerg, err, info, notice, and

     User Specification

      User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
                    (':' Host_List '=' Cmnd_Spec_List)*

      Cmnd_Spec_List ::= Cmnd_Spec |
                         Cmnd_Spec ',' Cmnd_Spec_List

      Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd

      Runas_Spec ::= '(' Runas_List ')'

      Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:')

     A user specification determines which commands a user may
     run (and as what user) on specified hosts.  By default, com-
     mands are run as root, but this can be changed on a per-
     command basis.

     Let's break that down into its constituent parts:


     A Runas_Spec is simply a Runas_List (as defined above)
     enclosed in a set of parentheses.  If you do not specify a
     Runas_Spec in the user specification, a default Runas_Spec
     of root will be used.  A Runas_Spec sets the default for

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     commands that follow it.  What this means is that for the

      dgb    boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm

     The user dgb may run /bin/ls, /bin/kill, and /usr/bin/lprm
     -- but only as operator.  E.g.,

      $ sudo -u operator /bin/ls.

     It is also possible to override a Runas_Spec later on in an
     entry.  If we modify the entry like so:

      dgb    boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm

     Then user dgb is now allowed to run /bin/ls as operator, but
     /bin/kill and /usr/bin/lprm as root.


     A command may have zero or more tags associated with it.
     There are four possible tag values, NOPASSWD, PASSWD,
     NOEXEC, EXEC. Once a tag is set on a Cmnd, subsequent Cmnds
     in the Cmnd_Spec_List, inherit the tag unless it is overrid-
     den by the opposite tag (ie: PASSWD overrides NOPASSWD and
     EXEC overrides NOEXEC).


     By default, sudo requires that a user authenticate him or
     herself before running a command.  This behavior can be
     modified via the NOPASSWD tag.  Like a Runas_Spec, the
     NOPASSWD tag sets a default for the commands that follow it
     in the Cmnd_Spec_List. Conversely, the PASSWD tag can be
     used to reverse things. For example:

      ray    rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm

     would allow the user ray to run /bin/kill, /bin/ls, and
     /usr/bin/lprm as root on the machine rushmore as root
     without authenticating himself.  If we only want ray to be
     able to run /bin/kill without a password the entry would be:

      ray    rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm

     Note, however, that the PASSWD tag has no effect on users
     who are in the group specified by the exempt_group option.

     By default, if the NOPASSWD tag is applied to any of the
     entries for a user on the current host, he or she will be
     able to run sudo -l without a password.  Additionally, a
     user may only run sudo -v without a password if the NOPASSWD

1.6.8p9                   June 20, 2005                        15


     tag is present for all a user's entries that pertain to the
     current host. This behavior may be overridden via the ver-
     ifypw and listpw options.

     NOEXEC and EXEC

     If sudo has been compiled with noexec support and the under-
     lying operating system support it, the NOEXEC tag can be
     used to prevent a dynamically-linked executable from running
     further commands itself.

     In the following example, user aaron may run /usr/bin/more
     and /usr/bin/vi but shell escapes will be disabled.

      aaron  shanty = NOEXEC: /usr/bin/more, /usr/bin/vi

     See the "PREVENTING SHELL ESCAPES" section below for more
     details on how noexec works and whether or not it will work
     on your system.


     sudo allows shell-style wildcards (aka meta or glob charac-
     ters) to be used in pathnames as well as command line argu-
     ments in the sudoers file.  Wildcard matching is done via
     the POSIX fnmatch(3) routine.  Note that these are not regu-
     lar expressions.

     *       Matches any set of zero or more characters.

     ?       Matches any single character.

     [...]   Matches any character in the specified range.

     [!...]  Matches any character not in the specified range.

     \x      For any character "x", evaluates to "x".  This is
             used to escape special characters such as: "*", "?",
             "[", and "}".

     Note that a forward slash ('/') will not be matched by wild-
     cards used in the pathname.  When matching the command line
     arguments, however, a slash does get matched by wildcards.
     This is to make a path like:


     match /usr/bin/who but not /usr/bin/X11/xterm.

     WARNING: a pathname with wildcards will not match a user
     command that consists of a relative path.  In other words,
     given the following sudoers entry:

1.6.8p9                   June 20, 2005                        16


         billy  workstation = /usr/bin/*

     user billy will be able to run any command in /usr/bin as
     root, such as /usr/bin/w.  The following two command will be
     allowed (the first assumes that /usr/bin is in the user's

         $ sudo w
         $ sudo /usr/bin/w

     However, this will not:

         $ cd /usr/bin
         $ sudo ./w

     For this reason you should only grant access to commands
     using wildcards and never restrict access using them.  This
     limitation will be removed in a future version of sudo.

     Exceptions to wildcard rules

     The following exceptions apply to the above rules:

     ""      If the empty string "" is the only command line
             argument in the sudoers entry it means that command
             is not allowed to be run with any arguments.

     Other special characters and reserved words

     The pound sign ('#') is used to indicate a comment (unless
     it occurs in the context of a user name and is followed by
     one or more digits, in which case it is treated as a uid).
     Both the comment character and any text after it, up to the
     end of the line, are ignored.

     The reserved word ALL is a built-in alias that always causes
     a match to succeed.  It can be used wherever one might oth-
     erwise use a Cmnd_Alias, User_Alias, Runas_Alias, or
     Host_Alias. You should not try to define your own alias
     called ALL as the built-in alias will be used in preference
     to your own.  Please note that using ALL can be dangerous
     since in a command context, it allows the user to run any
     command on the system.

     An exclamation point ('!') can be used as a logical not
     operator both in an alias and in front of a Cmnd.  This
     allows one to exclude certain values.  Note, however, that
     using a ! in conjunction with the built-in ALL alias to
     allow a user to run "all but a few" commands rarely works as
     intended (see SECURITY NOTES below).

1.6.8p9                   June 20, 2005                        17


     Long lines can be continued with a backslash ('\') as the
     last character on the line.

     Whitespace between elements in a list as well as special
     syntactic characters in a User Specification ('=', ':', '(',
     ')') is optional.

     The following characters must be escaped with a backslash
     ('\') when used as part of a word (e.g. a username or host-
     name): '@', '!', '=', ':', ',', '(', ')', '\'.


      /etc/sudoers           List of who can run what
      /etc/group             Local groups file
      /etc/netgroup          List of network groups


     Since the sudoers file is parsed in a single pass, order is
     important.  In general, you should structure sudoers such
     that the Host_Alias, User_Alias, and Cmnd_Alias specifica-
     tions come first, followed by any Default_Entry lines, and
     finally the Runas_Alias and user specifications.  The basic
     rule of thumb is you cannot reference an Alias that has not
     already been defined.

     Below are example sudoers entries.  Admittedly, some of
     these are a bit contrived.  First, we define our aliases:

      # User alias specification
      User_Alias     FULLTIMERS = millert, mikef, dowdy
      User_Alias     PARTTIMERS = bostley, jwfox, crawl
      User_Alias     WEBMASTERS = will, wendy, wim

      # Runas alias specification
      Runas_Alias    OP = root, operator
      Runas_Alias    DB = oracle, sybase

      # Host alias specification
      Host_Alias     SPARC = bigtime, eclipse, moet, anchor :\
                     SGI = grolsch, dandelion, black :\
                     ALPHA = widget, thalamus, foobar :\
                     HPPA = boa, nag, python
      Host_Alias     CUNETS =
      Host_Alias     CSNETS =,,
      Host_Alias     SERVERS = master, mail, www, ns
      Host_Alias     CDROM = orion, perseus, hercules

1.6.8p9                   June 20, 2005                        18


      # Cmnd alias specification
      Cmnd_Alias     DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
                             /usr/sbin/restore, /usr/sbin/rrestore
      Cmnd_Alias     KILL = /usr/bin/kill
      Cmnd_Alias     PRINTING = /usr/sbin/lpc, /usr/bin/lprm
      Cmnd_Alias     SHUTDOWN = /usr/sbin/shutdown
      Cmnd_Alias     HALT = /usr/sbin/halt
      Cmnd_Alias     REBOOT = /usr/sbin/reboot
      Cmnd_Alias     SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
                              /usr/local/bin/tcsh, /usr/bin/rsh, \
      Cmnd_Alias     SU = /usr/bin/su

     Here we override some of the compiled in default values.  We
     want sudo to log via syslog(3) using the auth facility in
     all cases.  We don't want to subject the full time staff to
     the sudo lecture, user millert need not give a password, and
     we don't want to reset the LOGNAME or USER environment vari-
     ables when running commands as root.  Additionally, on the
     machines in the SERVERS Host_Alias, we keep an additional
     local log file and make sure we log the year in each log
     line since the log entries will be kept around for several

      # Override built-in defaults
      Defaults               syslog=auth
      Defaults>root          !set_logname
      Defaults:FULLTIMERS    !lecture
      Defaults:millert       !authenticate
      Defaults@SERVERS       log_year, logfile=/var/log/sudo.log

     The User specification is the part that actually determines
     who may run what.

      root           ALL = (ALL) ALL
      %wheel         ALL = (ALL) ALL

     We let root and any user in group wheel run any command on
     any host as any user.


     Full time sysadmins (millert, mikef, and dowdy) may run any
     command on any host without authenticating themselves.


     Part time sysadmins (bostley, jwfox, and crawl) may run any
     command on any host but they must authenticate themselves
     first (since the entry lacks the NOPASSWD tag).

1.6.8p9                   June 20, 2005                        19


      jack           CSNETS = ALL

     The user jack may run any command on the machines in the
     CSNETS alias (the networks,, and Of those networks, only has an
     explicit netmask (in CIDR notation) indicating it is a class
     C network.  For the other networks in CSNETS, the local
     machine's netmask will be used during matching.

      lisa           CUNETS = ALL

     The user lisa may run any command on any host in the CUNETS
     alias (the class B network

                     sudoedit /etc/printcap, /usr/oper/bin/

     The operator user may run commands limited to simple mainte-
     nance. Here, those are commands related to backups, killing
     processes, the printing system, shutting down the system,
     and any commands in the directory /usr/oper/bin/.

      joe            ALL = /usr/bin/su operator

     The user joe may only su(1) to operator.

      pete           HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root

     The user pete is allowed to change anyone's password except
     for root on the HPPA machines.  Note that this assumes
     passwd(1) does not take multiple usernames on the command

      bob            SPARC = (OP) ALL : SGI = (OP) ALL

     The user bob may run anything on the SPARC and SGI machines
     as any user listed in the OP Runas_Alias (root and opera-

      jim            +biglab = ALL

     The user jim may run any command on machines in the biglab
     netgroup. Sudo knows that "biglab" is a netgroup due to the
     '+' prefix.

      +secretaries   ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser

     Users in the secretaries netgroup need to help manage the
     printers as well as add and remove users, so they are
     allowed to run those commands on all machines.

1.6.8p9                   June 20, 2005                        20


      fred           ALL = (DB) NOPASSWD: ALL

     The user fred can run commands as any user in the DB
     Runas_Alias (oracle or sybase) without giving a password.

      john           ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*

     On the ALPHA machines, user john may su to anyone except
     root but he is not allowed to give su(1) any flags.

      jen            ALL, !SERVERS = ALL

     The user jen may run any command on any machine except for
     those in the SERVERS Host_Alias (master, mail, www and ns).

      jill           SERVERS = /usr/bin/, !SU, !SHELLS

     For any machine in the SERVERS Host_Alias, jill may run any
     commands in the directory /usr/bin/ except for those com-
     mands belonging to the SU and SHELLS Cmnd_Aliases.

      steve          CSNETS = (operator) /usr/local/op_commands/

     The user steve may run any command in the directory
     /usr/local/op_commands/ but only as user operator.

      matt           valkyrie = KILL

     On his personal workstation, valkyrie, matt needs to be able
     to kill hung processes.

      WEBMASTERS     www = (www) ALL, (root) /usr/bin/su www

     On the host www, any user in the WEBMASTERS User_Alias
     (will, wendy, and wim), may run any command as user www
     (which owns the web pages) or simply su(1) to www.

      ALL            CDROM = NOPASSWD: /sbin/umount /CDROM,\
                     /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM

     Any user may mount or unmount a CD-ROM on the machines in
     the CDROM Host_Alias (orion, perseus, hercules) without
     entering a password. This is a bit tedious for users to
     type, so it is a prime candidate for encapsulating in a
     shell script.


     It is generally not effective to "subtract" commands from
     ALL using the '!' operator.  A user can trivially circumvent
     this by copying the desired command to a different name and
     then executing that.  For example:

1.6.8p9                   June 20, 2005                        21


         bill        ALL = ALL, !SU, !SHELLS

     Doesn't really prevent bill from running the commands listed
     in SU or SHELLS since he can simply copy those commands to a
     different name, or use a shell escape from an editor or
     other program.  Therefore, these kind of restrictions should
     be considered advisory at best (and reinforced by policy).


     Once sudo executes a program, that program is free to do
     whatever it pleases, including run other programs.  This can
     be a security issue since it is not uncommon for a program
     to allow shell escapes, which lets a user bypass sudo's res-
     trictions.  Common programs that permit shell escapes
     include shells (obviously), editors, paginators, mail and
     terminal programs.

     Many systems that support shared libraries have the ability
     to override default library functions by pointing an
     environment variable (usually LD_PRELOAD) to an alternate
     shared library. On such systems, sudo's noexec functionality
     can be used to prevent a program run by sudo from executing
     any other programs. Note, however, that this applies only to
     native dynamically-linked executables.  Statically-linked
     executables and foreign executables running under binary
     emulation are not affected.

     To tell whether or not sudo supports noexec, you can run the
     following as root:

         sudo -V | grep "dummy exec"

     If the resulting output contains a line that begins with:

         File containing dummy exec functions:

     then sudo may be able to replace the exec family of func-
     tions in the standard library with its own that simply
     return an error. Unfortunately, there is no foolproof way to
     know whether or not noexec will work at compile-time.
     Noexec should work on SunOS, Solaris, *BSD, Linux, IRIX,
     Tru64 UNIX, MacOS X, and HP-UX 11.x.  It is known not to
     work on AIX and UnixWare.  Noexec is expected to work on
     most operating systems that support the LD_PRELOAD environ-
     ment variable.  Check your operating system's manual pages
     for the dynamic linker (usually ld.so, ld.so.1, dyld,
     dld.sl, rld, or loader) to see if LD_PRELOAD is supported.

     To enable noexec for a command, use the NOEXEC tag as docu-
     mented in the User Specification section above.  Here is
     that example again:

1.6.8p9                   June 20, 2005                        22


      aaron  shanty = NOEXEC: /usr/bin/more, /usr/bin/vi

     This allows user aaron to run /usr/bin/more and /usr/bin/vi
     with noexec enabled.  This will prevent those two commands
     from executing other commands (such as a shell).  If you are
     unsure whether or not your system is capable of supporting
     noexec you can always just try it out and see if it works.

     Note that disabling shell escapes is not a panacea.  Pro-
     grams running as root are still capable of many potentially
     hazardous operations (such as changing or overwriting files)
     that could lead to unintended privilege escalation.  In the
     specific case of an editor, a safer approach is to give the
     user permission to run sudoedit.


     rsh(1), su(1), fnmatch(3), sudo(8), visudo(8)


     The sudoers file should always be edited by the visudo com-
     mand which locks the file and does grammatical checking. It
     is imperative that sudoers be free of syntax errors since
     sudo will not run with a syntactically incorrect sudoers

     When using netgroups of machines (as opposed to users), if
     you store fully qualified hostnames in the netgroup (as is
     usually the case), you either need to have the machine's
     hostname be fully qualified as returned by the hostname com-
     mand or use the fqdn option in sudoers.


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


     Commercial support is available for sudo, see
     http://www.sudo.ws/sudo/support.html for details.

     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.


     Sudo is provided ``AS IS'' and any express or implied war-
     ranties, including, but not limited to, the implied warran-
     ties 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

1.6.8p9                   June 20, 2005                        23

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