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   sudo    ( 8 )

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Описание (Description)

sudo allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy.

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

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

Security policies may support credential caching to allow the user to run sudo again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running sudo with the -v option, a user can update the cached credentials without running a command.

On systems where sudo is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced.

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

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

The options are as follows:

-A, --askpass Normally, if sudo requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example:

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

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

-B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used.

-b, --background Run the given command in the background. Note that it is not possible to use shell job control to manipulate background processes started by sudo. Most interactive commands will fail to work properly in background mode.

-C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, sudo will close all open file descriptors other than standard input, standard output and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option.

-D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory.

-E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment.

--preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times.

-e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken:

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

2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used.

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

To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy:

• Symbolic links may not be edited (version 1.8.15 and higher).

• Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher).

• Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher).

Users are never allowed to edit device special files.

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

-g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the '#' character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the '#' be escaped with a backslash ('\'). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use.

-H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior.

-h, --help Display a short help message to the standard output and exit.

-h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. Note that the sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host.

-i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login-specific resource files such as .profile, .bash_profile or .login will be read by the shell. If a command is specified, it is passed to the shell for execution via the shell's -c option. If no command is specified, an interactive shell is executed. sudo attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Note that most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use.

-K, --remove-timestamp Similar to the -k option, except that it removes the user's cached credentials entirely and may not be used in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching.

-k, --reset-timestamp When used without a command, invalidates the user's cached credentials. In other words, the next time sudo is run a password will be required. This option does not require a password and was added to allow a user to revoke sudo permissions from a .logout file.

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

Not all security policies support credential caching.

-l, --list If no command is specified, list the allowed (and forbidden) commands for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format.

If a command is specified and is permitted by the security policy, the fully-qualified path to the command is displayed along with any command line arguments. If a command is specified but not allowed by the policy, sudo will exit with a status value of 1.

-n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, sudo will display an error message and exit.

-P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user.

-p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent ('%') escape sequences are supported by the sudoers policy:

%H expanded to the host name including the domain name (on if the machine's host name is fully qualified or the fqdn option is set in sudoers(5))

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

%p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5))

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

%u expanded to the invoking user's login name

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

The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers.

-R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory.

-S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device.

-s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell for execution via the shell's -c option. If no command is specified, an interactive shell is executed. Note that most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details.

-U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. The sudoers policy only allows root or a user with the ALL privilege on the current host to use this option.

-T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the ability to set command timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled.

-u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the '#' character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the '#' be escaped with a backslash ('\'). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this.

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

-v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the sudo timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials.

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

Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input.

Environment variables to be set for the command may also be passed on the command line in the form of VAR=value, e.g., LD_LIBRARY_PATH=/usr/local/pkg/lib. Variables passed on the command line are subject to restrictions imposed by the security policy plugin. The sudoers policy subjects variables passed on the command line to the same restrictions as normal environment variables with one important exception. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information.