The major difference between sudo
and su
is the mechanism used to authenticate. With su
the user must know the root
password (which should be a closely guarded secret), while with sudo
the user uses his/her own password. In order to stop all users causing mayhem, the priviliges discharged by the sudo
command can, fortunately, be configured using the /etc/sudoers
file.
Both commands run a command as another user, quite often root
.
sudo su -
works in the example you gave because the user (or a group where the user is a member) is configured in the /etc/sudoers
file. That is, they are allowed to use sudo
. Armed with this, they use the sudo
to temporarily gain root
privileges (which is default when no username is provided) and as root
start another shell (su -
). They now have root
access without knowing root
's password.
Conversely, if you don't allow the user to use sudo
then they won't be able to sudo su -
.
Distros generally have a group (often called wheel
) whose members are allowed to use sudo
to run all commands. Removing them from this group will mean that they cannot use sudo
at all by default.
The line in /etc/sudoers
that does this is:
## Allows people in group wheel to run all commands
%wheel ALL=(ALL) ALL
While removing users from this group would make your system more secure, it would also result in you (or other system adminstrators) being required to carry out more administrative tasks on the system on behalf of your users.
A more sensible compromise would configure sudo
to give you more fine grained control of who is allowed to use sudo
and who isn't, along with which commands they are allowed to use (instead of the default of all commands). For example,
## Allows members of the users group to mount and unmount the
## cdrom as root
%users ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom
(only useful with the previous %wheel line commented out, or no users in the wheel
group).
Presumably, distros don't come with this finer grained configuration as standard as it's impossible to forecast what the admin's requirements are for his/her users and system.
Bottom line is - learn the details of sudo
and you can stop sudo su -
while allowing other commands that don't give the user root
shell access or access to commands that can change other users' files. You should give serious consideration to who you allow to use sudo
and to what level.
WARNING: Always use the visudo
command to edit the sudoers
file as it checks your edits for you and tries to save you from the embarrassing situation where a misconfigured file (due to a syntax error) stops you from using sudo
to edit any errors. This is especially true on Debian/Ubuntu and variants where the root
account is disabled by default.
Best Answer
It may be the case that your colleague, while creating the account, created the home directory "by hand" which resulted in it being owned by
root
. Try running the following asroot
:Where
username
is the name of the problematic account.Edit
If this turns out to be your problem, to avoid this happening in the future, you want to add the
-m
switch to theuseradd
command line used to create the user account. This ensures that the user's selected home directory is created if it doesn't exist. This creates the home directory with the "right" ownership and permissions so you don't face this kind of issue.Edit 2
The
chgrp
command added above will change group ownership of the entire home directory ofusername
tousername
's primary group. Depending on your environment, this may not be exactly what you want and you'll possibly need to change group ownership of specific sub-directories inside the home-directory "manually", thereby setting different group ownership for different sub-directories. This is usually not the case for personal computers, but since you mentioned "a colleague", I'm assuming we're talking about a networked office environment, in which case group ownership is important for shared directories.