What steps are needed to create a new user from the command line?

Solution 1:

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.

Solution 2:

To further automate this, the following line can be used to get the next "available" user id if you are running on a mac which already has users set up.

LastID=`dscl . -list /Users UniqueID | awk '{print $2}' | sort -n | tail -1`

NextID=$((LastID + 1))

Then, the corresponding line in bispymusic's answer above could be changed:

 dscl . create /Users/administrator UniqueID $NextID