# man > sudo
> **TLDR:** Execute a single command as the superuser or another user.
>
- Run a command as the superuser:
`sudo {{less /var/log/syslog}}`
- Edit a file as the superuser with your default editor:
`sudo {{-e|--edit}} {{/etc/fstab}}`
- Run a command as another user and/or group:
`sudo {{-u|--user}} {{user}} {{-g|--group}} {{group}} {{id -a}}`
- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):
`sudo !!`
- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):
`sudo {{-i|--login}}`
- Launch the default shell with superuser privileges without changing the environment:
`sudo {{-s|--shell}}`
- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):
`sudo {{-i|--login}} {{-u|--user}} {{user}}`
- List the allowed (and forbidden) commands for the invoking user in longer format:
`sudo {{-ll|--list --list}}`
*Source: tldr-pages*
---
[_SUDO_(8)](https://www.chedong.com/phpMan.php/man/SUDO/8/markdown) System Manager's Manual [_SUDO_(8)](https://www.chedong.com/phpMan.php/man/SUDO/8/markdown)
## 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 speci‐
fied by the security policy. The invoking user's real (_not_ effective) user-ID is used to de‐
termine the user name with which to query the security policy.
**sudo **supports a plugin architecture for security policies, auditing, and input/output log‐
ging. Third parties can develop and distribute their own 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 en‐
tered 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 cre‐
dentials on a per-terminal basis for 15 minutes. See the _timestamp_type_ and
_timestamp_timeout_ options in [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown), changes to the configuration files should be made using the [_visudo_(8)](https://www.chedong.com/phpMan.php/man/visudo/8/markdown)
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 attempts 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 exe‐
cuted 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)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) 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. It is not possible to use shell job control
to manipulate background processes started by **sudo**. Most interactive _command_s will
fail to work properly in background mode.
### -C _ --close-from
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 exe‐
cuting 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 _ --chdir
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 spec‐
ify the working directory.
### -E --preserve-env
Indicates to the security policy that the user wishes to preserve their existing en‐
vironment 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 secu‐
rity 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 _file_s 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 autho‐
rized 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 pro‐
gram listed in the _editor_ [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) option is used.
3. If they have been modified, the temporary files are copied back to their origi‐
nal location and the temporary versions are removed.
To help prevent the editing of unauthorized files, the following restrictions are en‐
forced 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 di‐
rectory 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. Unlike most _command_s 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 ver‐
sion, the user will receive a warning and the edited copy will remain in a temporary
file.
### -g _ --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 es‐
caped 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 **op‐
tion 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 direc‐
tory specified by the target user's password database entry. Depending on the pol‐
icy, this may be the default behavior.
### -h --help
Display a short help message to the standard output and exit.
### -h _ --host
Run the _command_ on the specified _host_ if the security policy plugin supports remote
_command_s. The _sudoers_ plugin does not currently support running remote _command_s. 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 as a simple _command_ using the **-c **option. The _command_ and any
_arg_s 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 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.
Most shells behave differently when a _command_ is specified as compared to an interac‐
tive session; consult the shell's manual for details. The _Command_ _environment_ sec‐
tion in the [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) 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 entered 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 credentials for the cur‐
rent 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 **com‐
mands run in a different terminal session. See the _timestamp_type_ option in
[_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) for more information. 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 privileges 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 for the invoking
user (or the, _user_ specified by the **-U **option) on the current host, the fully-quali‐
fied path to the _command_ is displayed along with any _arg_s. 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 policy, **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 authenti‐
cates. 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 authentication 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 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
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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown))
%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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown))
%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 _ --chroot
Change to the specified root _directory_ (see [_chroot_(8)](https://www.chedong.com/phpMan.php/man/chroot/8/markdown)) before running the _command_.
The security policy may return an error if the user does not have permission to spec‐
ify the root directory.
### -r _ --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 _arg_s 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 exe‐
cuted. Most shells behave differently when a _command_ is specified as compared to an
interactive session; consult the shell's manual for details.
### -t _ --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 _ --other-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 _ --command-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
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 ‘#’ char‐
acter (e.g., ‘#0’ for UID 0). When running _command_s 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 any configured plug‐
ins. 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. Subsequent options are passed
to the _command_.
Options that take a value may only be specified once unless otherwise indicated in the de‐
scription. This is to help guard against problems caused by poorly written scripts that in‐
voke **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
subject 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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) for more information.
## COMMAND EXECUTION
When **sudo **executes a _command_, the security policy specifies the execution 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 explic‐
itly requests it, a new pseudo-terminal (“pty”) is allocated and [_fork_(2)](https://www.chedong.com/phpMan.php/man/fork/2/markdown) is used to create a
second **sudo **process, referred 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)](https://www.chedong.com/phpMan.php/man/fork/2/markdown) again, sets
up the execution environment as described above, and then uses the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) 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 signals 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)](https://www.chedong.com/phpMan.php/man/fork/2/markdown), sets up the execution environment as described above,
and uses the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) 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
security policy's close function, as well as the close function of any configured audit plug‐
ins, 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)](https://www.chedong.com/phpMan.php/man/fork/2/markdown) 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 responsible 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 pre‐
vents the _command_ from receiving SIGINT twice each time the user enters control-C. Some sig‐
nals, 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 sus‐
pend 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)](https://www.chedong.com/phpMan.php/man/reboot/8/markdown)
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)](https://www.chedong.com/phpMan.php/man/reboot/8/markdown),
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)](https://www.chedong.com/phpMan.php/man/reboot/8/markdown) or [_shutdown_(8)](https://www.chedong.com/phpMan.php/man/shutdown/8/markdown) via **sudo **may cause the system to end up
in this undefined state unless the [_reboot_(8)](https://www.chedong.com/phpMan.php/man/reboot/8/markdown) or [_shutdown_(8)](https://www.chedong.com/phpMan.php/man/shutdown/8/markdown) are run using the **exec**() family
of functions instead of **system**() (which interposes a shell between the _command_ and the call‐
ing process).
### Plugins
Plugins may be specified via _Plugin_ directives in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file is present, or if it doesn't contain any _Plugin_ lines, **sudo**
will use [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) for the policy, auditing, and I/O logging plugins. See the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown)
manual for details of the _/etc/sudo.conf_ file and the [_sudo_plugin_(5)](https://www.chedong.com/phpMan.php/man/sudoplugin/5/markdown) manual for more informa‐
tion 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 problem, 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)](https://www.chedong.com/phpMan.php/man/stat/2/markdown) one or more entries in the
user's PATH, an error is printed to the standard error. (If the directory does not exist or
if it is not really a directory, the entry is ignored and no error is printed.) This should
not happen under normal circumstances. The most common reason for [_stat_(2)](https://www.chedong.com/phpMan.php/man/stat/2/markdown) 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 _command_s.
To prevent command spoofing, **sudo **checks "." and "" (both denoting current directory) last
when searching for a _command_ in the user's PATH (if one or both are in the PATH). 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 re‐
place the _command_ there is no way to limit what additional _command_s 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 _command_s run from that shell are not subject to **sudo**'s
security policy. The same is true for _command_s that offer shell escapes (including most edi‐
tors). If I/O logging is enabled, subsequent _command_s will have their input and/or output
logged, but there will not be traditional logs for those _command_s. Because of this, care must
be taken when giving users access to _command_s via **sudo **to verify that the _command_ does not
inadvertently give the user an effective root shell. For information on ways to address
this, see the _Preventing_ _shell_ _escapes_ section in [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown).
To prevent the disclosure of potentially sensitive information, **sudo **disables core dumps by
default while it is executing (they are re-enabled for the _command_ that is run). This his‐
torical 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)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file as follows:
Set disable_coredump false
See the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) 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_ op‐
tion 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 ter‐
minal is available or if the **-A **option is specified.
SUDO_COMMAND Set to the _command_ run by sudo, including any _arg_s. The _arg_s 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 **option 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 system 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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown)
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)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) for more information.
### 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 unpriv‐
ileged 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 per‐
missions 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 unprivileged uid.
### fatal error, unable to load plugins
An error occurred while loading or initializing the plugins specified in [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown).
### invalid environment variable name
One or more environment variable names specified via the **-E **option contained an equal
sign (‘=’). The arguments to the **-E **option should be environment variable names with‐
out an associated value.
### no password was provided
When **sudo **tried to read the password, it did not receive any characters. This may hap‐
pen if no terminal is available (or the **-S **option is specified) and the standard input
has been redirected from _/dev/null_.
### a terminal is required to read the password
**sudo **needs to read the password but there is no mechanism available 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)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) 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 interme‐
diate 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 con‐
tainer that sets this flag. Check the documentation to see if it is possible to con‐
figure 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 setting 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)](https://www.chedong.com/phpMan.php/man/su/1/markdown), [_stat_(2)](https://www.chedong.com/phpMan.php/man/stat/2/markdown), [_login_cap_(3)](https://www.chedong.com/phpMan.php/man/logincap/3/markdown), [_passwd_(5)](https://www.chedong.com/phpMan.php/man/passwd/5/markdown), [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown), [_sudo_plugin_(5)](https://www.chedong.com/phpMan.php/man/sudoplugin/5/markdown), [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown),
[_sudoers_timestamp_(5)](https://www.chedong.com/phpMan.php/man/sudoerstimestamp/5/markdown), [_sudoreplay_(8)](https://www.chedong.com/phpMan.php/man/sudoreplay/8/markdown), [_visudo_(8)](https://www.chedong.com/phpMan.php/man/visudo/8/markdown)
## HISTORY
See the HISTORY.md file in the **sudo **distribution () for a
brief history of sudo.
## AUTHORS
Many people have worked on **sudo **over the years; this version consists of code written primar‐
ily by:
Todd C. Miller
See the CONTRIBUTORS.md file in the **sudo **distribution (‐
tors/) 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
_command_s via shell escapes, thus avoiding **sudo**'s checks. However, on most systems it is pos‐
sible to prevent shell escapes with the [_sudoers_(5)](https://www.chedong.com/phpMan.php/man/sudoers/5/markdown) 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 generally safe).
## BUGS
If you believe you have found a bug in **sudo**, you can submit a bug report at
## SUPPORT
Limited free support is available via the sudo-users mailing list, see
to subscribe or search the archives.
## DISCLAIMER
**sudo **is provided “AS IS” and any express or implied warranties, including, but not limited
to, the implied warranties of merchantability and fitness for a particular purpose are dis‐
claimed. See the LICENSE.md file distributed with **sudo **or
for complete details.
Sudo 1.9.15p5 August 9, 2023 [_SUDO_(8)](https://www.chedong.com/phpMan.php/man/SUDO/8/markdown)