sudo (superuser do) allows you to configure non-root users to run root level commands without being root. Access can be given by the root level administrator through configuration of the /etc/sudoers file. Please note that making changes directly to the /etc/sudoers file is discouraged, and that the visudo utility should be used.
The syntax for using sudo is fairly simple, you specify the name of the command preceded by 'sudo'. For example, if a user needed to run /sbin/chown, you could run it with the command:
sudo /sbin/chown <user_name> <file_name>
Which would then prompt you for the root password and then run the command. You can configure sudo to allow access to files by using the root password, the user's own password, or with no password.
Configuring who's password to use
Here is how to configure each:
1. For non-root user access by entering the root password:
2. For non-root user access by entering their own password:
# In the default (unconfigured) configuration, sudo asks for the root password. # This allows use of an ordinary user account for administration of a freshly # installed system. When configuring sudo, delete the two # following lines: # Defaults targetpw # ask for the password of the target user i.e. root # ALL ALL=(ALL) ALL # WARNING! Only use this together with 'Defaults targetpw'!
3. For non-root user access by entering no password:
# User privilege specification root ALL=(ALL) ALL <user_name> ALL=NOPASSWD: ALL
Setting up permissions for non-root users
Now that you know how to change what password to use (or not to use), let's move on to permissions.
In the "User privilege specification" section, you can set privileges at the user or group levels. Here is what it looks like by default:
# User privilege specification root ALL=(ALL) ALL # Uncomment to allow people in group wheel to run all commands # %wheel ALL=(ALL) ALL # Same thing without a password # %wheel ALL=(ALL) NOPASSWD: ALL # Samples # %users ALL=/sbin/mount /cdrom,/sbin/umount /cdrom # %users localhost=/sbin/shutdown -h now
To give privileges to users, add users to the area under the "User privilege specification". As an example, to give a user named Joe privileges to run chown, you would add the following entry:
# User privilege specification root ALL=(ALL) ALL Joe ALL=PASSWD: /bin/chown
Using this syntax, all options for chown will be available to Joe. If you want to limit what parameters can be used by Joe, list them in the entry like this:
# User privilege specification root ALL=(ALL) ALL Joe ALL=PASSWD: /bin/chown -R, /bin/chown -V, /bin/chown -R-V
Notice that there are three separate entries. One that allows -R, one for -V, and one for -R-V. sudo allows will only allow multiple parameters if you add them specifically (and only in the order that you specify), thus the -R-V in addition to the individual parameter listings.
You can also allow some commands to be used with no password while others require a password. Here is an example:
Joe ALL=NOPASSWD: \ /bin/chown -R, PASSWD: /bin/chown -V, /bin/chown -R-V
With the above configuration, the /bin/chown -R command will not require a password, /bin/chown -V and /bin/chown -R-V will require a password to run, but they will be allowed.
The same thing can be done for user groups, you just need to put it in the following syntax:
# Uncomment to allow people in group wheel to run all commands # %wheel ALL=(ALL) ALL # Same thing without a password # %wheel ALL=(ALL) NOPASSWD: ALL # Samples # %users ALL=/sbin/mount /cdrom,/sbin/umount /cdrom # %users localhost=/sbin/shutdown -h now
You just need to specify the group name with a % in front of it. The same syntax for users applies to groups.
With resent sudo versions the /etc/sudoers include the following syntax:
## Read drop-in files from /etc/sudoers.d @includedir /etc/sudoers.d
With above syntax, new configuration could be added without updating /etc/sudoers. For full information, kindly check the manual pages: man sudoers