root


Sudo is a program designed to allow a sysadmin to allow selected users to execute some commands as root. The basic philosophy is to give as few privileges as possible but still allow people to get their work done. Sudo is also an effective way to log root activities.

Sudo isn't enabled by default on Debian

Strictly speaking, sudo is installed and enabled, but no rights are granted by default in Debian (as opposed to some others distributions).

How to execute a command as root: (in a default Debian installation)

  • When you installed the system, you chose a password for the root account.

  • Gnome prompts for that password (for the Administrative account) when you want to start that would run as root.

  • To execute a command as root, open a terminal as root (Applications > Accessories > Root Terminal), or run su from a regular terminal.

Now, if you want to allow certain users to execute certain programs, here's a a quick example (for more information, read the fine manual).

# /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
#

Defaults        env_reset

# Host alias specification
User_Alias      MYADMINS = jdoe

# User alias specification

# Cmnd alias specification
Cmnd_Alias      SHUTDOWN = /sbin/shutdown, /sbin/reboot, /sbin/halt
Cmnd_Alias      PKGMGMT = /usr/bin/dpkg, /usr/bin/apt-get, /usr/bin/aptitude

# User privilege specification

# Users listed above (MYADMINS) can run package managers and reboot the system.
MYADMINS ALL = PKGMGMT, SHUTDOWN

# Users in the group wheel can execute any command impersonating any user.
#%wheel ALL= ALL

#Default rule for root.
root    ALL=(ALL) ALL

Troubles and tweaks

Sorry, user jdoe is not allowed to execute ...

A typical session goes like this:

This messages typically means that the user isn't allowed to execute the action.

sudoers is read-only

Yes, the file /etc/sudoers is set read-only, even for root!

The is because, one must use the command visudo to edit /etc/sudoers.

CVE-2005-4158

With the fix for CVE-2005-4158: Insecure handling of PERLLIB PERL5LIB PERL5OPT environment vars, the default behaviour of handling environment variables was switched to protect against malicious local users with sudo privileges getting sudo to do more than the malcontent was given privileges to do.

As a result, unless you modify your sudoers file to contain Defaults env_reset, you may experience problems using sudo like the following:

If you had more complex setups where you meant to pass through environment variables, your work around may be more complex or no longer possible.

Bug: #342948

PASSWD option not working

sudo has a flag called exempt_group which contains a list of groups for which always NOPASSWD is true and setting PASSWD has no effect. On Debian Systems this list consists of the group sudo.

See also