The difference between .command, .tool, and .sh file extensions

OS X handles sudo and su identically to Linux.

sudo is a command that, without any additional options, will run a command as root. For example:

% touch /newfile
touch: /newfile: Permission denied
% ls -l /newfile
ls: /newfile: No such file or directory
% sudo touch /newfile
% ls -l /newfile 
-rw-r--r--  1 root  wheel  0 Apr 27 11:45 /newfile

su on the other hand, will switch the current user to root (again without any extra commands). In the example below, I have to run sudo su, since I don't know the root password for my system:

% whoami
alake
% sudo su
$ whoami
root

The key difference between sudo and su is sudo runs a command as root, whereas su makes you root. Much like other command line utilities there are a number of alternative ways to use both sudo and su, if you're interested you can always run man <command> eg. man sudo to get more information.

Here is a shell script I wrote at work to handle this as part of the NetInstall process (creating a local administrator account automatically during imaging process).

#!/bin/sh
. /etc/rc.common
dscl . create /Users/administrator
dscl . create /Users/administrator RealName "Administrator Account"
dscl . create /Users/administrator hint "Password Hint"
dscl . create /Users/administrator picture "/Path/To/Picture.png"
dscl . passwd /Users/administrator thisistheaccountpassword
dscl . create /Users/administrator UniqueID 501
dscl . create /Users/administrator PrimaryGroupID 80
dscl . create /Users/administrator UserShell /bin/bash
dscl . create /Users/administrator NFSHomeDirectory /Users/administrator
cp -R /System/Library/User\ Template/English.lproj /Users/administrator
chown -R administrator:staff /Users/administrator

Some notes to mention:

• I have this saved as an executable ".sh" file.
• Since it executes during NetInstall it runs as root, and needs to run as root to work properly. You can also subtract the first two lines, add a "sudo" to the beginning of each subsequent line, and manually run these as individual commands in Terminal.
• Modify UniqueID from 501 to a number that you will know is safe on all systems (501 is taken by the first account created on a Mac, generally something higher like 550 will probably be safe, depending on how many users you have on your system).
• PrimaryGroupID of 80 creates an Admin user. Change to PrimaryGroupID of 20 to create a Standard user.
• I've imaged well over 50 Macs this way with no issues. I use this account to run commands via SSH, to push out patches via ARD and to do local desk-side administration.