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Options Guide for SUDO

always_set_home
If set, sudo will set the HOME environment variable to the home directory of the target user (which is root unless the -u option is used). This effectively means that the -H option is always implied. [D: OFF]
askpass
The askpass option specifies 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.
authenticate
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 .closefrom_override If set, the user may use sudo's -C option which overrides the default starting point at which sudo begins closing open file descriptors. [D: OFF]
closefrom
Before it executes a command, sudo will close all open file descriptors other than standard input, standard output and standard error (ie: file descriptors 0-2). The closefrom option can be used to specify a different file descriptor at which to start closing. The default is 3.
editor
A colon (':') separated list of editors allowed to be used with visudo. visudo will choose the editor that matches the user's EDITOR 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.
env_check
Environment variables to be removed from the user's environment if the variable's value contains % or / characters. This can be used to guard against printf- style format vulnerabilities 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 disabled by using the =, +=, -=, and ! operators respectively. Regardless of whether the env_reset option is enabled or disabled, variables specified by env_check will be preserved in the environment if they pass the aforementioned check. The default list of environment variables to check is displayed when sudo is run by root with the -V option.
env_delete
Environment variables to be removed from the user's environment when the env_reset option is not in effect. 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. The default list of environment variables to remove is displayed 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_editor
If set, visudo will use the value of the EDITOR or VISUAL environment variables before falling 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.
env_file
The env_file options specifies the fully qualified path to a file containing variables to be set in the environment of the program being run. Entries in this file should either be of the form VARIABLE=value or export VARIABLE=value. The value may optionally be surrounded by single or double quotes. Variables in this file are subject to other sudo environment settings such as env_keep and env_check .exempt_group Users in this group are exempt from password and PATH requirements. This is not set by default.
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. The default list of variables to keep is displayed when sudo is run by root with the -V option .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 warning.
env_reset
If set, sudo will reset the environment to only contain the LOGNAME, SHELL, USER, USERNAME and the SUDO_* variables. Any variables in the caller's environment that match the env_keep and env_check lists are then added. The default contents of the env_keep and env_check lists are displayed when sudo is run by root with the -V option. If the secure_path option is set, its value will be used for the PATH environment variable. This flag is on by default.
fast_glob
Normally, sudo uses the glob(3) function to do shell- style globbing when matching pathnames. However, since it accesses the file system, glob(3) can take a long time to complete for some patterns, especially when the pattern references a network file system that is mounted on demand (automounted). The fast_glob option causes sudo to use the fnmatch(3) function, which does not access the file system to do its matching .The disadvantage of fast_glob is that it is unable to match relative pathnames such as ./ls or ../bin/ls. [D: OFF]
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 hostname (as returned by the hostname command) is already fully qualified you shouldn't need to set fqdn. [D: OFF]
ignore_dot
If set, sudo will ignore '.' or '' (current dir) in the PATH environment variable; the PATH itself is not modified. [D: OFF].ignore_local_sudoers If set via LDAP, parsing of /etc/sudoers will be skipped. This is intended for Enterprises 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 /etc/sudoers. When this option is present, /etc/sudoers does not even need to exist. Since this option tells sudo how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the cn=defaults section. [D: OFF]
insults
If set, sudo will insult users when they enter an incorrect password. This flag is on by default.
lecture
This option controls when a short lecture will be printed along with the password prompt. It has the following possible values:
  • [always] Always lecture the user.
  • [never] Never lecture the user.
  • [once] Only lecture the user the first time they run sudo.
If no value is specified, a value of once is implied. Negating the option results in a value of never being used.
listpw
This option controls when a password will be required when a user runs sudo with the -l option. 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.
  • [always] The user must always enter a password to use the -l option.
  • [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 option.
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.
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. By default, sudo logs via syslog .mailerflags Flags to use when invoking mailer. Defaults to -t.
log_host
If set, the hostname will be logged in the (non-syslog) sudo log file. [D: OFF]
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 word wrap).
log_year
If set, the four-digit year will be logged in the (non- syslog) sudo log file. [D: OFF].long_otp_prompt When validating with a One Time Password (OPT) scheme such as 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. [D: OFF]
mail_always
Send mail to the mailto user every time a users runs sudo
mail_badpass
Send mail to the mailto user if the user running sudo does not enter the correct password. [D: OFF]
mailerpath
Path to mail program used to send warning mail. Defaults to the path to sendmail found at configure time.
mailfrom
Address to use for the "from" address when sending warning and error mail. The address should be enclosed in double quotes (") to protect against sudo interpreting the @ sign. Defaults to the name of the user running sudo.
mail_no_host
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. [D: OFF]
mail_no_perms
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. [D: OFF]
mail_no_user
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.
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 ***.
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 .secure_path Path used for every command run from sudo. If you don't trust the people running sudo to have a sane PATH environment variable you may want to use this. Another use is if you want to have the "root path" be separate from the "user path." Users in the group specified by the exempt_group option are not affected by secure_path. This option is not set by default.
noexec
If set, all commands run via sudo will behave as if the NOEXEC tag has been set, unless overridden 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. [D: OFF]
noexec_file
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/libexec/sudo_noexec.so.
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 following percent (%) escapes are supported:
  • [%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)
  • [%h] expanded to the local hostname without the domain name
  • [%p] expanded to the user whose password is being asked for (respects the rootpw, targetpw and runaspw flags in sudoers)
  • [%U] expanded to the login name of the user the command will be run as (defaults to root)
  • [%u] expanded to the invoking user's login name
  • [%%] two consecutive % characters are collapsed into a single % character
The default value is SUDO Password: .
passwd_timeout
Number of minutes before the sudo password prompt times. The default is 150; set this to 0 for no password timeout. timestamp_timeout Number of minutes that can elapse before sudo will ask for a passwd again. The default is 1440. Set this to 0 to always prompt for a password. If set to a value less than 0 the user's timestamp will never expire. This can be used to allow users to create or delete their own timestamps via sudo -v and sudo -k respectively.
passwd_tries
The number of tries a user gets to enter his/her password before sudo logs the failure and exits. The default is 8 .Integers that can be used in a boolean context:
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 confusing. This flag is on by default .passprompt_override The password prompt specified by passprompt will normally only be used if the passwod prompt provided by systems such as PAM matches the string "Password:". If passprompt_override is set, passprompt will always be used. [D: OFF].preserve_groups 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. [D: OFF]
pwfeedback
By default, sudo reads the password like most other Unix programs, by turning off echo until the user hits the return (or enter) key. Some users become confused by this as it appears to them that sudo has hung at this point. When pwfeedback is set, sudo will provide visual feedback when the user presses a key. Note that this does have a security impact as an onlooker may be able to determine the length of the password being entered .[D: OFF]
requiretty
If set, sudo will only run when the user is logged in to a real tty. When this flag is set, sudo can only be run from a login session and not via other means such as cron(8) or cgi-bin scripts. [D: OFF]
rootpw
If set, sudo will prompt for the root password instead of the password of the invoking user. [D: OFF]
root_sudo
If set, root is allowed to run sudo too. Disabling 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 provides no real additional security; it exists purely for historical reasons. This flag is on by default.
runas_default
The default user to run commands as if the -u option 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 specifications.
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. [D: OFF]
setenv
Allow the user to disable the env_reset option from the command line. Additionally, environment variables set via the command line are not subject to the restrictions imposed by env_check, env_delete, or env_keep. As such, only trusted users should be allowed to set variables in this manner. [D: OFF]
set_home
If set and sudo is invoked with the -s option 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 option imply -H. [D: OFF]
set_logname
Normally, sudo will set the LOGNAME, USER and USERNAME environment variables to the name of the target user (usually root unless the -u option is given). However, since some programs (including the RCS revision control system) use LOGNAME to determine the real identity of the user, it may be desirable to change this behavior. This can be done by negating the set_logname option. Note that if the env_reset option has not been disabled, entries in the env_keep list will override the value of set_logname. [D: OFF]
shell_noargs
If set and sudo is invoked with no arguments it acts as if the -s option 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). [D: OFF]
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 useful on systems that disable some potentially dangerous functionality when a program is run setuid. This option is only effective on systems with either the setreuid() or setresuid() function. [D: OFF]
sudoers_locale
Locale to use when parsing the sudoers file. Note that changing the locale may affect how sudoers is interpreted. Defaults to "C".
syslog
Syslog facility if syslog is being used for logging (negate to disable syslog logging). Defaults to local2.
syslog_badpri
Syslog priority to use when user authenticates successfully. Defaults to alert.
syslog_goodpri
Syslog priority to use when user authenticates successfully. Defaults to notice.
targetpw
If set, sudo will prompt for the password of the user specified by the -u option (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 option. [D: OFF]
timestampdir
The directory in which sudo stores its timestamp files. The default is /var/run/sudo.
timestampowner
The owner of the timestamp directory and the timestamps stored therein. The default is root .Strings that can be used in a boolean context:
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 running it. With this flag enabled, sudo will use a file named for the tty the user is logged in on in that directory. [D: OFF]
umask
Umask to use when running the command. Negate this option or set it to 0777 to preserve the user's umask. The actual umask that is used will be the union of the user's umask and 0022. This guarantees that sudo never lowers the umask when running a command. Note on systems that use PAM, the default PAM configuration may specify its own umask which will override the value set in sudoers .Strings: badpass_message Message that is displayed if a user enters an incorrect. The default is AHHH, bad password! Try again! unless insults are enabled.
umask_override
If set, sudo will set the umask as specified by sudoers without modification. This makes it possible to specify a more permissive umask in sudoers than the user's own umask and matches historical behavior. If umask_override is not set, sudo will set the umask to be the union of the user's umask and what is specified in sudoers. [D: OFF]
verifypw
This option controls when a password will be required when a user runs sudo with the -v option. 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.
  • [always] The user must always enter a password to use the -v option.
  • [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 option.
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
visiblepw
By default, sudo will refuse to run if the user must enter a password but it is not possible to disable echo on the terminal. If the visiblepw flag is set, sudo will prompt for a password even when it would be visible on the screen. This makes it possible to run things like "rsh somehost sudo ls" since rsh(1) does not allocate a tty. [D: OFF].

Defaults /etc/sudoers Cheatsheet

Here is a commented out list of all the options available to use with the Defaults command in /etc/sudoers. The idea is to copy and paste this in your sudoers files and then make changes.

sudoers-defaults-cheatsheet

#Defaults       always_set_home
# always_set_home: If enabled, sudo will set the HOME environment variable to the home directory of the target user (which is root unless the -u option is used).  This effectively means that the -H op
#     always_set_home is only effective for configurations where either env_reset is disabled or HOME is present in the env_keep list.  This flag is off by default.
 
#Defaults       authenticate
# authenticate: 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 t
 
#Defaults       closefrom_override
# closefrom_override: If set, the user may use sudo's -C option which overrides the default starting point at which sudo begins closing open file descriptors.  This flag is off by default.
 
#Defaults       compress_io
# compress_io: If set, and sudo is configured to log a command's input or output, the I/O logs will be compressed using zlib.  This flag is on by default when sudo is compiled with zlib support.
 
#Defaults       env_editor
# env_editor: If set, visudo will use the value of the EDITOR or VISUAL environment variables before falling back on the default editor list.  Note that this may create a security hole as it allows th
#   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.
 
#Defaults       env_reset
# env_reset: If set, sudo will run the command in a minimal environment containing the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables.  Any variables in the caller's envir
#   in the file specified by the env_file option (if any).  The default contents of the env_keep and env_check lists are displayed when sudo is run by root with the -V option.  If the secure_path opti
#   default.
 
#Defaults       fast_glob
# fast_glob: Normally, sudo uses the glob(3) function to do shell-style globbing when matching path names.  However, since it accesses the file system, glob(3) can take a long time to complete for som
#   (automounted).  The fast_glob option causes sudo to use the fnmatch(3) function, which does not access the file system to do its matching.  The disadvantage of fast_glob is that it is unable to ma
#   names that include globbing characters are used with the negation operator, '!', as such rules can be trivially bypassed.  As such, this option should not be used when sudoers contains rules that
 
#Defaults       fqdn
# fqdn: Set this flag if you want to put fully qualified host names 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
#   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
#     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.
 
#Defaults       ignore_dot
# 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.
 
#Defaults       ignore_local_sudoers
# ignore_local_sudoers: If set via LDAP, parsing of /etc/sudoers will be skipped.  This is intended for Enterprises that wish to prevent the usage of local sudoers files so that only LDAP is used.  Th
#   present, /etc/sudoers does not even need to exist. Since this option tells sudo how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the cn=default
 
#Defaults       insults
# insults: If set, sudo will insult users when they enter an incorrect password.  This flag is off by default.
 
#Defaults       log_host
# log_host: If set, the host name will be logged in the (non-syslog) sudo log file.  This flag is off by default.
 
#Defaults       log_input
# log_input: If set, sudo will run the command in a pseudo tty and log all user input.  If the standard input is not connected to the user's tty, due to I/O redirection or because the command is part
#   Input is logged to the directory specified by the iolog_dir option (/var/log/sudo-io by default) using a unique session ID that is included in the normal sudo log line, prefixed with TSID=.  The i
#   Note that user input may contain sensitive information such as passwords (even if they are not echoed to the screen), which will be stored in the log file unencrypted.  In most cases, logging the
 
#Defaults       log_output
# log_output: If set, sudo will run the command in a pseudo tty and log all output that is sent to the screen, similar to the script(1) command.  If the standard output or standard error is not connec
#   is also captured and stored in separate log files.
#   Output is logged to the directory specified by the iolog_dir option (/var/log/sudo-io by default) using a unique session ID that is included in the normal sudo log line, prefixed with TSID=.  The
#   Output logs may be viewed with the sudoreplay(8) utility, which can also be used to list or search the available logs.
 
#Defaults       log_year
# log_year: If set, the four-digit year will be logged in the (non-syslog) sudo log file.  This flag is off by default.
 
#Defaults       long_otp_prompt
# long_otp_prompt: When validating with a One Time Password (OTP) scheme such as 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
 
#Defaults       mail_always
# mail_always: Send mail to the mailto user every time a users runs sudo.  This flag is off by default.
 
#Defaults       mail_badpass
# mail_badpass: Send mail to the mailto user if the user running sudo does not enter the correct password.  This flag is off by default.
 
#Defaults       mail_no_host
# mail_no_host: 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.
 
#Defaults       mail_no_perms
# mail_no_perms: 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 den
 
#Defaults       mail_no_user
# mail_no_user: 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.
 
#Defaults       noexec
# noexec: If set, all commands run via sudo will behave as if the NOEXEC tag has been set, unless overridden by a EXEC tag.  See the description of NOEXEC and EXEC below as well as the "PREVENTING SHE
 
#Defaults       path_info
# 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 t
#   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 confusing.  This flag is on by default.
 
#Defaults       passprompt_override
# passprompt_override: The password prompt specified by passprompt will normally only be used if the password prompt provided by systems such as PAM matches the string "Password:".  If passprompt_over
 
#Defaults       preserve_groups
# preserve_groups: 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
#   default.
 
#Defaults       pwfeedback
# pwfeedback: By default, sudo reads the password like most other Unix programs, by turning off echo until the user hits the return (or enter) key.  Some users become confused by this as it appears to
#   the user presses a key.  Note that this does have a security impact as an onlooker may be able to determine the length of the password being entered.  This flag is off by default.
 
#Defaults       requiretty
# requiretty: If set, sudo will only run when the user is logged in to a real tty.  When this flag is set, sudo can only be run from a login session and not via other means such as cron(8) or cgi-bin
 
#Defaults       root_sudo
# root_sudo: If set, root is allowed to run sudo too.  Disabling this prevents users from "chaining" sudo commands to get a root shell by doing something like "sudo sudo /bin/sh".  Note, however, that
#   real additional security; it exists purely for historical reasons.  This flag is on by default.
 
#Defaults       rootpw
# rootpw: If set, sudo will prompt for the root password instead of the password of the invoking user.  This flag is off by default.
 
#Defaults       runaspw
# 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.
 
#Defaults       set_home
# set_home: If enabled and sudo is invoked with the -s option 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 eff
#   is enabled, so set_home is only effective for configurations where either env_reset is disabled or HOME is present in the env_keep list.  This flag is off by default.
 
#Defaults       set_logname
# set_logname: Normally, sudo will set the LOGNAME, USER and USERNAME environment variables to the name of the target user (usually root unless the -u option is given).  However, since some programs (
#   may be desirable to change this behavior.  This can be done by negating the set_logname option.  Note that if the env_reset option has not been disabled, entries in the env_keep list will override
 
#Defaults       set_utmp
# set_utmp: When enabled, sudo will create an entry in the utmp (or utmpx) file when a pseudo-tty is allocated.  A pseudo-tty is allocated by sudo when the log_input, log_output or use_pty flags are e
#   the tty, time, type and pid fields updated.  This flag is on by default.
 
#Defaults       setenv
# setenv: Allow the user to disable the env_reset option from the command line via the -E option.  Additionally, environment variables set via the command line are not subject to the restrictions impo
#   variables in this manner.  This flag is off by default.
 
#Defaults       shell_noargs
# shell_noargs: If set and sudo is invoked with no arguments it acts as if the -s option had been given.  That is, it runs a shell as root (the shell is determined by the SHELL environment variable if
#   is off by default.
 
#Defaults       stay_setuid
# 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
#   systems that disable some potentially dangerous functionality when a program is run setuid.  This option is only effective on systems with either the setreuid() or setresuid() function.  This flag
 
#Defaults       targetpw
# targetpw: If set, sudo will prompt for the password of the user specified by the -u option (defaults to root) instead of the password of the invoking user.  In addition, the timestamp file name will
#   passwd database as an argument to the -u option.  This flag is off by default.
 
#Defaults       tty_tickets
# tty_tickets: If set, users must authenticate on a per-tty basis.  With this flag enabled, sudo will use a file named for the tty the user is logged in on in the user's time stamp directory.  If disa
 
#Defaults       umask_override
# umask_override: If set, sudo will set the umask as specified by sudoers without modification.  This makes it possible to specify a more permissive umask in sudoers than the user's own umask and matc
#   user's umask and what is specified in sudoers.  This flag is off by default.
 
#Defaults       use_pty
# use_pty: If set, sudo will run the command in a pseudo-pty even if no I/O logging is being gone.  A malicious program run under sudo could conceivably fork a background process that retains to the u
#   that impossible.  This flag is off by default.
 
#Defaults       utmp_runas
# utmp_runas: If set, sudo will store the name of the runas user when updating the utmp (or utmpx) file.  By default, sudo stores the name of the invoking user.  This flag is off by default.
 
#Defaults       visiblepw
# visiblepw: By default, sudo will refuse to run if the user must enter a password but it is not possible to disable echo on the terminal.  If the visiblepw flag is set, sudo will prompt for a passwor
#   somehost sudo ls" since rsh(1) does not allocate a tty.  This flag is off by default.
 
#Defaults       closefrom
# closefrom: Before it executes a command, sudo will close all open file descriptors other than standard input, standard output and standard error (ie: file descriptors 0-2).  The closefrom option can
 
#Defaults       passwd_tries
# passwd_tries: The number of tries a user gets to enter his/her password before sudo logs the failure and exits.  The default is 3.
 
#Defaults       loglinelen
# 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
 
#Defaults       passwd_timeout
# passwd_timeout: Number of minutes before the sudo password prompt times out, or 0 for no timeout.  The timeout may include a fractional component if minute granularity is insufficient, for example 2
 
#Defaults       timestamp_timeout
# timestamp_timeout: Number of minutes that can elapse before sudo will ask for a passwd again.  The timeout may include a fractional component if minute granularity is insufficient, for example 2.5.
#   timestamp will never expire.  This can be used to allow users to create or delete their own timestamps via sudo -v and sudo -k respectively.
 
#Defaults       umask
# umask: Umask to use when running the command.  Negate this option or set it to 0777 to preserve the user's umask.  The actual umask that is used will be the union of the user's umask and the value o
#   running a command.  Note on systems that use PAM, the default PAM configuration may specify its own umask which will override the value set in sudoers.
 
#Defaults       badpass_message
# badpass_message: Message that is displayed if a user enters an incorrect password.  The default is Sorry, try again. unless insults are enabled.
 
#Defaults       editor
# editor: A colon (':') separated list of editors allowed to be used with visudo.  visudo will choose the editor that matches the user's EDITOR environment variable if possible, or the first editor in
 
#Defaults       iolog_dir
# iolog_dir: The top-level directory to use when constructing the path name for the input/output log directory.  Only used if the log_input or log_output options are enabled or when the LOG_INPUT or L
#   directory.  The default is "/var/log/sudo-io".
#   The following percent (%) escape sequences are supported:
#     %{seq} - expanded to a monotonically increasing base-36 sequence number, such as 0100A5, where every two digits are used to form a new directory, e.g. 01/00/A5
#     %{user} - expanded to the invoking user's login name
#     %{group} - expanded to the name of the invoking user's real group ID
#     %{runas_user} - expanded to the login name of the user the command will be run as (e.g. root)
#     %{runas_group} - expanded to the group name of the user the command will be run as (e.g. wheel)
#     %{hostname} - expanded to the local host name without the domain name
#     %{command} - expanded to the base name of the command being run
#   In addition, any escape sequences supported by the system's strftime() function will be expanded.
#   To include a literal % character, the string %% should be used.
 
#Defaults       iolog_file
# iolog_file: The path name, relative to iolog_dir, in which to store input/output logs when the log_input or log_output options are enabled or when the LOG_INPUT or LOG_OUTPUT tags are present for a
#   See the iolog_dir option above for a list of supported percent (%) escape sequences.
#   In addition to the escape sequences, path names that end in six or more Xs will have the Xs replaced with a unique combination of digits and letters, similar to the mktemp() function.
 
#Defaults       mailsub
# mailsub: Subject of the mail sent to the mailto user. The escape %h will expand to the host name of the machine.  Default is *** SECURITY information for %h ***.
 
#Defaults       noexec_file
# noexec_file: This option is no longer supported.  The path to the noexec file should now be set in the /etc/sudo.conf file.
 
#Defaults       passprompt
# 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 following percent (%) escape sequences are suppo
#     %H  expanded to the local host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set)
#     %h  expanded to the local host name without the domain name
#     %p  expanded to the user whose password is being asked for (respects the rootpw, targetpw and runaspw flags in sudoers)
#     %U  expanded to the login name of the user the command will be run as (defaults to root)
#     %u  expanded to the invoking user's login name
#     %%  two consecutive % characters are collapsed into a single % character
#   The default value is Password:.
 
#Defaults       runas_default
# runas_default: The default user to run commands as if the -u option is not specified on the command line.  This defaults to root.
 
#Defaults       syslog_badpri
# syslog_badpri: Syslog priority to use when user authenticates unsuccessfully.  Defaults to alert.
#   The following syslog priorities are supported: alert, crit, debug, emerg, err, info, notice, and warning.
 
#Defaults       syslog_goodpri
# syslog_goodpri: Syslog priority to use when user authenticates successfully.  Defaults to notice.
#   See syslog_badpri for the list of supported syslog priorities.
 
#Defaults       sudoers_locale
# sudoers_locale: Locale to use when parsing the sudoers file, logging commands, and sending email.  Note that changing the locale may affect how sudoers is interpreted.  Defaults to "C".
 
#Defaults       timestampdir
# timestampdir: The directory in which sudo stores its timestamp files.  The default is /var/db/sudo.
 
#Defaults       timestampowner
# timestampowner: The owner of the timestamp directory and the timestamps stored therein.  The default is root.
 
#Defaults       env_file
# env_file: The env_file option specifies the fully qualified path to a file containing variables to be set in the environment of the program being run.  Entries in this file should either be of the f
#   quotes.  Variables in this file are subject to other sudo environment settings such as env_keep and env_check.
 
#Defaults       exempt_group
# exempt_group: Users in this group are exempt from password and PATH requirements.  The group name specified should not include a % prefix.  This is not set by default.
 
#Defaults       group_plugin
# group_plugin: A string containing a sudoers group plugin with optional arguments.  This can be used to implement support for the nonunix_group syntax described earlier.  The string should consist of
#   configuration arguments the plugin requires.  These arguments (if any) will be passed to the plugin's initialization function.  If arguments are present, the string must be enclosed in double quot
#   For example, given /etc/sudo-group, a group file in Unix group format, the sample group plugin can be used:
#   Defaults group_plugin="sample_group.so /etc/sudo-group"
#   For more information see sudo_plugin(5).
 
#Defaults       lecture
# lecture: This option controls when a short lecture will be printed along with the password prompt.  It has the following possible values:
#     always  Always lecture the user.
#     never   Never lecture the user.
#     once    Only lecture the user the first time they run sudo.
#   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.
 
#Defaults       lecture_file
# lecture_file: Path to a file containing an alternate sudo lecture that will be used in place of the standard lecture if the named file exists.  By default, sudo uses a built-in lecture.
 
#Defaults       listpw
# listpw: This option controls when a password will be required when a user runs sudo with the -l option.  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.
#     always  The user must always enter a password to use the -l option.
#     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 option.
#   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.
 
#Defaults       logfile
# 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.  By default, sudo logs via syslog.
 
#Defaults       mailerflags
# mailerflags: Flags to use when invoking mailer. Defaults to -t.
 
#Defaults       mailerpath
# mailerpath: Path to mail program used to send warning mail.  Defaults to the path to sendmail found at configure time.
 
#Defaults       mailfrom
# mailfrom: Address to use for the "from" address when sending warning and error mail.  The address should be enclosed in double quotes (") to protect against sudo interpreting the @ sign.  Defaults t
 
#Defaults       mailto
# 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.
 
#Defaults       secure_path
# secure_path: Path used for every command run from sudo.  If you don't trust the people running sudo to have a sane PATH environment variable you may want to use this.  Another use is if you want to
#   option are not affected by secure_path.  This option is not set by default.
 
#Defaults       syslog
# syslog: Syslog facility if syslog is being used for logging (negate to disable syslog logging).  Defaults to auth.
#   The following syslog facilities are supported: authpriv (if your OS supports it), auth, daemon, user, local0, local1, local2, local3, local4, local5, local6, and local7.
 
#Defaults       verifypw
# verifypw: This option controls when a password will be required when a user runs sudo with the -v option.  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.
#     always  The user must always enter a password to use the -v option.
#     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 option.
#   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.
 
#Defaults       env_check
# env_check: Environment variables to be removed from the user's environment if the variable's value contains % or / characters.  This can be used to guard against printf-style format vulnerabilities
#   value without double-quotes.  The list can be replaced, added to, deleted from, or disabled by using the =, +=, -=, and ! operators respectively.  Regardless of whether the env_reset option is ena
#   they pass the aforementioned check.  The default list of environment variables to check is displayed when sudo is run by root with the -V option.
 
#Defaults       env_delete
# env_delete: Environment variables to be removed from the user's environment when the env_reset option is not in effect.  The argument may be a double-quoted, space-separated list or a single value w
#   +=, -=, and ! operators respectively.  The default list of environment variables to remove is displayed when sudo is run by root with the -V option.  Note that many operating systems will remove p
 
#Defaults       env_keep
# 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 r
#   quotes.  The list can be replaced, added to, deleted from, or disabled by using the =, +=, -=, and ! operators respectively.  The default list of variables to keep is displayed when sudo is run by

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September 28th, 2012

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Hacking and Hackers

The use of "hacker" to mean "security breaker" is a confusion on the part of the mass media. We hackers refuse to recognize that meaning, and continue using the word to mean someone who loves to program, someone who enjoys playful cleverness, or the combination of the two. See my article, On Hacking.
-- Richard M. Stallman






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