#Bash 的 sudo 命令
sudo [OPTION]...
功能
以其它用户的身份执行程序。
类型
可执行文件（/usr/bin/sudo），属于 sudo。
参数
OPTION选项：-A,--askpass- 通过辅助程序（可能是 GUI）询问密码-B,--bell- 询问密码时响铃；使用--askpass时此选项无效-b,--background- 在后台运行程序-C num,--close-from=num- 执行命令前关闭文件描述符大于或等于num的所有文件；num不能小于 3-D directory,--chdir=directory- 指定directory作为执行命令时的工作目录-E,--preserve-env- 保留当前用户的环境变量；默认情况下，执行命令前会重置环境变量--preserve-env=list- 保留当前用户的部分环境变量；使用逗号分隔-e,--edit- 编辑文件而非执行命令；不能编辑可写目录里的文件-g group,--group=group- 设置执行命令时的主要组-H,--set-home- 执行命令时将HOME设为目标用户在/etc/passwd中配置的主目录-h host,--host=host- 在指定的主机上远程执行命令-i,--login- 运行目标用户在/etc/passwd中配置的登录 shell-K,--remove-timestamp- 删除缓存的凭据-k,--reset-timestamp- 无CMD参数时使缓存的凭据失效，下次必须输入密码；有CMD时必须输入密码并且不缓存凭据-l,--list- 无CMD时列出sudo组的用户列表；有CMD时显示CMD的完整路径及所有参数-N,--no-update- 不更新缓存凭据-n,--non-interactive- 不提示用户输入；如果需要输入密码则报错-P,--preserve-groups- 除实际组和有效组以为的组保持不变-p prompt,--prompt=prompt- 指定密码提示符-R directory,--chroot=directory- 指定directory作为执行命令时的 root 目录-r role,--role=role- 使用包含指定角色的 SELinux 安全上下文执行程序-S,--stdin- 将提示符写入标准错误输出，并从标准输入读取密码；而不是使用终端设备-s,--shell- 如果有SHELL环境变量则运行该 shell；否则运行目标用户在/etc/passwd中配置的登录 shell-t type,--type=type- 使用包含指定类型的 SELinux 安全上下文执行程序-U user,--other-user=user- 与-l选项组合使用，列出user用户的权限-T timeout,--command-timeout=timeout-u user,--user=user- 以user用户身份执行命令；默认为root用户-v,--validate- 更新用户缓存凭据-h,--help- 显示帮助-V,--version- 显示版本
CMD- 要执行的命令ARGS- 传递给CMD的参数
#示例
以 root 用户的身份执行命令
$ ls /root
ls: cannot open directory '/root': Permission denied
$ sudo ls /root # 以 root 用户的身份执行命令
file1 file2 file3
以 root 用户的身份编辑文件
$ sudo -e /root/file # 以 root 用户的身份编辑文件
以其它用户的身份执行命令
$ ls /home/user2
ls: cannot open directory '/home/user2': Permission denied
$ sudo -u user2 ls /root # 以 user2 用户的身份执行命令
file1 file2 file3
#推荐阅读
#手册
SUDO(8) System Manager's Manual SUDO(8)
NAME
sudo, sudoedit — execute a command as another user
SYNOPSIS
sudo -h | -K | -k | -V
sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user]
sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user]
[command [arg ...]]
sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host]
[-p prompt] [-R directory] [-r role] [-t type] [-T timeout]
[-u user] [VAR=value] [-i | -s] [command [arg ...]]
sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host]
[-p prompt] [-R directory] [-r role] [-t type] [-T timeout]
[-u user] file ...
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, auditing,
and input/output logging. Third parties can develop and distribute
their own plugins to work seamlessly with the sudo front-end. The de‐
fault security policy is sudoers, which is configured via the file
/etc/sudoers, or via LDAP. See the “Plugins” section for more informa‐
tion.
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 0
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 ba‐
sis for 15 minutes. See the timestamp_type and timestamp_timeout op‐
tions 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 privi‐
leges, 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 and audit plugins may log successful and failed at‐
tempts to run 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 er‐
ror.
-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. 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 cur‐
rent working directory. The security policy may return an er‐
ror 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 pre‐
serve their existing environment variables. The security pol‐
icy 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 pre‐
served from the user's environment. The security policy may
return an error if the user does not have permission to pre‐
serve 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 tem‐
porary 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 follow‐
ing 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 invok‐
ing user may not be edited unless that user is root (ver‐
sion 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. Un‐
like most commands run by sudo, the editor is run with the in‐
voking 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 data‐
base 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 op‐
tion 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 vari‐
able to the home directory specified by the target user's pass‐
word 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. 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 privi‐
leges 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 re‐
source 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 as a simple command using the -c option. The command
and any args are concatenated, separated by spaces, after es‐
caping each character (including white space) with a backslash
(‘\’) except for alphanumerics, underscores, hyphens, and dol‐
lar signs. If no command is specified, an interactive shell is
executed. sudo attempts to change to that user's home direc‐
tory before running the shell. The command is run with an en‐
vironment similar to the one a user would receive at log in.
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 every cached
credential for the user, regardless of the terminal or parent
process ID. The next time sudo is run, a password must be en‐
tered if the security policy requires authentication. It is
not possible to use the -K option 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 cre‐
dentials for the current session. The next time sudo is run in
the session, a password must be entered if the security policy
requires authentication. By default, the sudoers policy uses a
separate record in the credential cache for each terminal (or
parent process ID if no terminal is present). This prevents
the -k option from interfering with sudo commands run in a dif‐
ferent terminal session. See the timestamp_type option in
sudoers(5) for more information. This option does not require
a password, and was added to allow a user to revoke sudo per‐
missions 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 privileges for the invok‐
ing user (or the user specified by the -U option) on the cur‐
rent 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 pol‐
icy for the invoking user (or the, user specified by the -U op‐
tion) on the current host, the fully-qualified path to the
command is displayed along with any args. If -l is specified
more than once (and the security policy supports it), the
matching rule is displayed in a verbose format along with the
command. If a command is specified but not allowed by the pol‐
icy, sudo will exit with a status value of 1.
-N, --no-update
Do not update the user's cached credentials, even if the user
successfully authenticates. Unlike the -k flag, existing
cached credentials are used if they are valid. To detect when
the user's cached credentials are valid (or when no authentica‐
tion is required), the following can be used:
sudo -Nnv
Not all security policies support credential caching.
-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 de‐
fault, 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 (only
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 spec‐
ified)
%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 vari‐
able. 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 direc‐
tory.
-r role, --role=role
Run the command with an SELinux security context that includes
the specified role.
-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 as a simple command using the -c option. The command and
any args are concatenated, separated by spaces, after escaping
each character (including white space) with a backslash (‘\’)
except for alphanumerics, underscores, hyphens, and dollar
signs. If no command is specified, an interactive shell is ex‐
ecuted. Most shells behave differently when a command is spec‐
ified as compared to an interactive session; consult the
shell's manual for details.
-t type, --type=type
Run the command with an SELinux security context that includes
the specified type. If no type is specified, the default type
is derived from the role.
-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. When using the
sudoers policy, the -U option is restricted to the root user
and users with either the “list” priviege for the specified
user or the ability to run any command as root or user on the
current host.
-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 user's ability to set
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 nu‐
meric user-ID (UID) prefixed with the ‘#’ character (e.g., ‘#0’
for UID 0). When running commands as a UID, many shells re‐
quire that the ‘#’ be escaped with a backslash (‘\’). Some se‐
curity policies may restrict UIDs to those listed in the pass‐
word 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
any configured plugins. If the invoking user is already root,
the -V option will display the options passed to configure when
sudo was built; plugins may display additional 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 15 minutes by default, but does not run a
command. Not all security policies support cached credentials.
-- The -- is used to delimit the end of the sudo options. Subse‐
quent options are passed to the command.
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 as
options to sudo in the form VAR=value, for example
LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be sub‐
ject to restrictions imposed by the security policy plugin. The
sudoers policy subjects environment variables passed as options to the
same restrictions as existing environment variables with one important
difference. 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.
COMMAND EXECUTION
When sudo executes a command, the security policy specifies the execu‐
tion environment for the command. Typically, the real and effective
user and group and IDs are set to match those of the target user, as
specified in the password database, and the group vector is initialized
based on the group database (unless the -P option was specified).
The following parameters may be specified by security policy:
• real and effective user-ID
• real and effective group-ID
• supplementary group-IDs
• the environment list
• current working directory
• file creation mode mask (umask)
• SELinux role and type
• scheduling priority (aka nice value)
Process model
There are two distinct ways sudo can run a command.
If an I/O logging plugin is configured to log terminal I/O, or if the
security policy explicitly requests it, a new pseudo-terminal (“pty”)
is allocated and fork(2) is used to create a second sudo process, re‐
ferred to as the monitor. The monitor creates a new terminal session
with itself as the leader and the pty as its controlling terminal,
calls fork(2) again, sets up the execution environment as described
above, and then uses the execve(2) system call to run the command in
the child process. The monitor exists to relay job control signals be‐
tween the user's terminal and the pty the command is being run in.
This makes it possible to suspend and resume the command normally.
Without the monitor, the command would be in what POSIX terms an
“orphaned process group” and it would not receive any job control sig‐
nals from the kernel. When the command exits or is terminated by a
signal, the monitor passes the command's exit status to the main sudo
process and exits. After receiving the command's exit status, the main
sudo process passes the command's exit status to the security policy's
close function, as well as the close function of any configured audit
plugin, and exits. This mode is the default for sudo versions 1.9.14
and above when using the sudoers policy.
If no pty is used, sudo calls fork(2), sets up the execution environ‐
ment as described above, and uses the execve(2) system call to run the
command in the child process. The main sudo process waits until the
command has completed, then passes the command's exit status to the se‐
curity policy's close function, as well as the close function of any
configured audit plugins, and exits. As a special case, if the policy
plugin does not define a close function, sudo will execute the command
directly instead of calling fork(2) first. The sudoers policy plugin
will only define a close function when I/O logging is enabled, a pty is
required, an SELinux role is specified, the command has an associated
timeout, or the pam_session or pam_setcred options are enabled. Both
pam_session and pam_setcred are enabled by default on systems using
PAM. This mode is the default for sudo versions prior to 1.9.14 when
using the sudoers policy.
On systems that use PAM, the security policy's close function is re‐
sponsible for closing the PAM session. It may also log the command's
exit status.
Signal handling
When the command is run as a child of the sudo process, sudo will relay
signals it receives to the command. The SIGINT and SIGQUIT signals are
only relayed when the command is being run in a new pty or when the
signal was sent by a user process, not the kernel. This prevents the
command from receiving SIGINT twice each time the user enters control-
C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and
thus will not be relayed to the command. As a general rule, SIGTSTP
should be used instead of SIGSTOP when you wish to suspend a command
being run by sudo.
As a special case, sudo will not relay signals that were sent by the
command it is running. This prevents the command from accidentally
killing itself. On some systems, the reboot(8) utility sends SIGTERM
to all non-system processes other than itself before rebooting the sys‐
tem. This prevents sudo from relaying the SIGTERM signal it received
back to reboot(8), which might then exit before the system was actually
rebooted, leaving it in a half-dead state similar to single user mode.
Note, however, that this check only applies to the command run by sudo
and not any other processes that the command may create. As a result,
running a script that calls reboot(8) or shutdown(8) via sudo may cause
the system to end up in this undefined state unless the reboot(8) or
shutdown(8) are run using the exec() family of functions instead of
system() (which interposes a shell between the command and the calling
process).
Plugins
Plugins may be specified via Plugin directives in the sudo.conf(5)
file. They may be loaded as dynamic shared objects (on systems that
support them), or compiled directly into the sudo binary. If no
sudo.conf(5) file is present, or if it doesn't contain any Plugin
lines, sudo will use sudoers(5) for the policy, auditing, and I/O log‐
ging plugins. See the sudo.conf(5) manual for details of the
/etc/sudo.conf file and the sudo_plugin(5) manual for more information
about the sudo plugin architecture.
EXIT VALUE
Upon successful execution of a command, the exit status from sudo will
be the exit status of the program that was executed. If the command
terminated due to receipt of a signal, sudo will send itself the same
signal that terminated the command.
If the -l option was specified without a command, sudo will exit with a
value of 0 if the user is allowed to run sudo and they authenticated
successfully (as required by the security policy). If a command is
specified with the -l option, the exit value will only be 0 if the
command is permitted by the security policy, otherwise it will be 1.
If there is an authentication failure, a configuration/permission prob‐
lem, or if the given command cannot be executed, sudo exits with a
value of 1. In the latter case, the error string is printed to the
standard error. If sudo cannot stat(2) one or more entries in the
user's PATH, an error is printed to the standard error. (If the direc‐
tory does not exist or if it is not really a directory, the entry is
ignored and no error is printed.) This should not happen under normal
circumstances. The most common reason for stat(2) to return
“permission denied” is if you are running an automounter and one of the
directories in your PATH is on a machine that is currently unreachable.
SECURITY NOTES
sudo tries to be safe when executing external commands.
To prevent command spoofing, sudo checks "." and "" (both denoting cur‐
rent directory) last when searching for a command in the user's PATH
(if one or both are in the PATH). Depending on the security policy,
the user's PATH environment variable may be modified, replaced, or
passed unchanged to the program that sudo executes.
Users should never be granted sudo privileges to execute files that are
writable by the user or that reside in a directory that is writable by
the user. If the user can modify or replace the command there is no
way to limit what additional commands they can run.
By default, sudo will only log the command it explicitly runs. If a
user runs a command such as ‘sudo su’ or ‘sudo sh’, subsequent commands
run from that shell are not subject to sudo's security policy. The
same is true for commands that offer shell escapes (including most edi‐
tors). If I/O logging is enabled, subsequent commands will have their
input and/or output logged, but there will not be traditional logs for
those commands. Because of this, care must be taken when giving users
access to commands via sudo to verify that the command does not inad‐
vertently give the user an effective root shell. For information on
ways to address this, see the Preventing shell escapes section in
sudoers(5).
To prevent the disclosure of potentially sensitive information, sudo
disables core dumps by default while it is executing (they are re-en‐
abled for the command that is run). This historical practice dates
from a time when most operating systems allowed set-user-ID processes
to dump core by default. To aid in debugging sudo crashes, you may
wish to re-enable core dumps by setting “disable_coredump” to false in
the sudo.conf(5) file as follows:
Set disable_coredump false
See the sudo.conf(5) manual for more information.
ENVIRONMENT
sudo utilizes the following environment variables. The security policy
has control over the actual content of the command's environment.
EDITOR Default editor to use in -e (sudoedit) mode if neither
SUDO_EDITOR nor VISUAL is set.
MAIL Set to the mail spool of the target user when the -i
option is specified, or when env_reset is enabled in
sudoers (unless MAIL is present in the env_keep list).
HOME Set to the home directory of the target user when the
-i or -H options are specified, when the -s option is
specified and set_home is set in sudoers, when
always_set_home is enabled in sudoers, or when
env_reset is enabled in sudoers and HOME is not
present in the env_keep list.
LOGNAME Set to the login name of the target user when the -i
option is specified, when the set_logname option is
enabled in sudoers, or when the env_reset option is
enabled in sudoers (unless LOGNAME is present in the
env_keep list).
PATH May be overridden by the security policy.
SHELL Used to determine shell to run with -s option.
SUDO_ASKPASS Specifies the path to a helper program used to read
the password if no terminal is available or if the -A
option is specified.
SUDO_COMMAND Set to the command run by sudo, including any args.
The args are truncated at 4096 characters to prevent a
potential execution error.
SUDO_EDITOR Default editor to use in -e (sudoedit) mode.
SUDO_GID Set to the group-ID of the user who invoked sudo.
SUDO_PROMPT Used as the default password prompt unless the -p op‐
tion was specified.
SUDO_PS1 If set, PS1 will be set to its value for the program
being run.
SUDO_UID Set to the user-ID of the user who invoked sudo.
SUDO_USER Set to the login name of the user who invoked sudo.
USER Set to the same value as LOGNAME, described above.
VISUAL Default editor to use in -e (sudoedit) mode if
SUDO_EDITOR is not set.
FILES
/etc/sudo.conf sudo front-end configuration
EXAMPLES
The following examples assume a properly configured security policy.
To get a file listing of an unreadable directory:
$ sudo ls /usr/local/protected
To list the home directory of user yaz on a machine where the file sys‐
tem holding ~yaz is not exported as root:
$ sudo -u yaz ls ~yaz
To edit the index.html file as user www:
$ sudoedit -u www ~www/htdocs/index.html
To view system logs only accessible to root and users in the adm group:
$ sudo -g adm more /var/log/syslog
To run an editor as jim with a different primary group:
$ sudoedit -u jim -g audio ~jim/sound.txt
To shut down a machine:
$ sudo shutdown -r +15 "quick reboot"
To make a usage listing of the directories in the /home partition. The
commands are run in a sub-shell to allow the ‘cd’ command and file
redirection to work.
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
DIAGNOSTICS
Error messages produced by sudo include:
editing files in a writable directory is not permitted
By default, sudoedit does not permit editing a file when any of
the parent directories are writable by the invoking user. This
avoids a race condition that could allow the user to overwrite an
arbitrary file. See the sudoedit_checkdir option in sudoers(5)
for more information.
editing symbolic links is not permitted
By default, sudoedit does not follow symbolic links when opening
files. See the sudoedit_follow option in sudoers(5) for more in‐
formation.
effective uid is not 0, is sudo installed setuid root?
sudo was not run with root privileges. The sudo binary must be
owned by the root user and have the set-user-ID bit set. Also,
it must not be located on a file system mounted with the ‘nosuid’
option or on an NFS file system that maps uid 0 to an unprivi‐
leged uid.
effective uid is not 0, is sudo on a file system with the 'nosuid'
option set or an NFS file system without root privileges?
sudo was not run with root privileges. The sudo binary has the
proper owner and permissions but it still did not run with root
privileges. The most common reason for this is that the file
system the sudo binary is located on is mounted with the ‘nosuid’
option or it is an NFS file system that maps uid 0 to an unprivi‐
leged uid.
fatal error, unable to load plugins
An error occurred while loading or initializing the plugins spec‐
ified in sudo.conf(5).
invalid environment variable name
One or more environment variable names specified via the -E op‐
tion contained an equal sign (‘=’). The arguments to the -E op‐
tion should be environment variable names without an associated
value.
no password was provided
When sudo tried to read the password, it did not receive any
characters. This may happen if no terminal is available (or the
-S option is specified) and the standard input has been redi‐
rected from /dev/null.
a terminal is required to read the password
sudo needs to read the password but there is no mechanism avail‐
able for it to do so. A terminal is not present to read the
password from, sudo has not been configured to read from the
standard input, the -S option was not used, and no askpass helper
has been specified either via the sudo.conf(5) file or the
SUDO_ASKPASS environment variable.
no writable temporary directory found
sudoedit was unable to find a usable temporary directory in which
to store its intermediate files.
The “no new privileges” flag is set, which prevents sudo from running
as root.
sudo was run by a process that has the Linux “no new privileges”
flag is set. This causes the set-user-ID bit to be ignored when
running an executable, which will prevent sudo from functioning.
The most likely cause for this is running sudo within a container
that sets this flag. Check the documentation to see if it is
possible to configure the container such that the flag is not
set.
sudo must be owned by uid 0 and have the setuid bit set
sudo was not run with root privileges. The sudo binary does not
have the correct owner or permissions. It must be owned by the
root user and have the set-user-ID bit set.
sudoedit is not supported on this platform
It is only possible to run sudoedit on systems that support set‐
ting the effective user-ID.
timed out reading password
The user did not enter a password before the password timeout (5
minutes by default) expired.
you do not exist in the passwd database
Your user-ID does not appear in the system passwd database.
you may not specify environment variables in edit mode
It is only possible to specify environment variables when running
a command. When editing a file, the editor is run with the
user's environment unmodified.
SEE ALSO
su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5),
sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8)
HISTORY
See the HISTORY.md file in the sudo distribution
(https://www.sudo.ws/about/history/) for a brief history of sudo.
AUTHORS
Many people have worked on sudo over the years; this version consists
of code written primarily by:
Todd C. Miller
See the CONTRIBUTORS.md file in the sudo distribution
(https://www.sudo.ws/about/contributors/) for an exhaustive list of
people who have contributed to sudo.
CAVEATS
There is no easy way to prevent a user from gaining a root shell if
that user is allowed to run arbitrary commands via sudo. Also, many
programs (such as editors) allow the user to run commands via shell es‐
capes, thus avoiding sudo's checks. However, on most systems it is
possible to prevent shell escapes with the sudoers(5) plugin's noexec
functionality.
It is not meaningful to run the ‘cd’ command directly via sudo, e.g.,
$ sudo cd /usr/local/protected
since when the command exits the parent process (your shell) will still
be the same. The -D option can be used to run a command in a specific
directory.
Running shell scripts via sudo can expose the same kernel bugs that
make set-user-ID shell scripts unsafe on some operating systems (if
your OS has a /dev/fd/ directory, set-user-ID shell scripts are gener‐
ally safe).
BUGS
If you believe you have found a bug in sudo, you can submit a bug re‐
port at https://bugzilla.sudo.ws/
SUPPORT
Limited free support is available via the sudo-users mailing list, see
https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search
the archives.
DISCLAIMER
sudo is provided “AS IS” and any express or implied warranties, includ‐
ing, but not limited to, the implied warranties of merchantability and
fitness for a particular purpose are disclaimed. See the LICENSE.md
file distributed with sudo or https://www.sudo.ws/about/license/ for
complete details.
Sudo 1.9.15p5 August 9, 2023 SUDO(8)