How to use Terminal, launched from OSX setup screen, to create new user?

I need to create a new user account on a system drive (10.10.1) because I am unable to log in to the only existing one. I can however get into the OSX setup from a prepared USB flash drive, and launch Terminal there.

I guess it would be possible to add the user account "testuser" with the following method:

dscl . create /Users/testuser
dscl . create /Users/testuser UserShell /bin/bash
dscl . create /Users/testuser RealName "Test User"
dscl . create /Users/testuser UniqueID 503
dscl . create /Users/testuser PrimaryGroupID 1000
dscl . create /Users/testuser NFSHomeDirectory /Local/Users/testuser
dscl . passwd /Users/testuser PASSWORD
dscl . append /Groups/admin GroupMembership testuser

Now entering

-bash-3.2# dscl . create /Users/testuser

what I get from Terminal is this:

-bash: dscl: command not found

I am not the most experienced with command line tools, and am clueless on how to get it to work. Any help is greatly appreciated.

Solution

I'm not sure how you prepared the USB drive, but it looks like it doesn't include dscl. You can use the copy of dscl from the regular startup volume, but it'd still be trying to create a user on the USB disk. To fix that, you'd need to use dscl's -f option to point it to the user database you actually wanted to edit (see here for something similar).

"/Volumes/Macintosh HD/usr/bin/dscl" -f "/Volumes/Macintosh HD/var/db/dslocal/nodes/Default" localonly -create /Local/Target/Users/testuser

...etc. But even then, I'm not sure it'll handle setting the user's password correctly (there used to be a bug relating to that, but I think it got fixed).

There's a much easier way. Just delete the file /var/db/.AppleSetupDone from your regular volume (not the USB disk):

rm "/Volumes/Macintosh HD/var/db/.AppleSetupDone"

... then reboot normally and it'll run through the Setup Assistant, including letting you create a new admin account (note that existing accounts will be preserved). You can use the new admin to clean up whatever needs to be fixed (reset PW on old admin account?), then delete it when everything is back to normal.