They are probably there, but missing from your $PATH. As root (use the su
command to become root, don't log in as the root user) type echo $PATH
. If the resulting list lacks /sbin, /usr/sbin and /usr/local/sbin you can add them permanently to your path by editing root's ~/.bashrc and adding the following line:
You can make the changes take effect immidiately by typing source ~/.bashrc
(still as root). Echo your $PATH again and you should see the sbin dirs in the list of directories that are searched for executables.
Or, if all this seems like it's not worth it just type the full path to the commands, which are typically located in /usr/sbin, so you would type /usr/sbin/useradd
and so on.