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Shortly before the period starts, you'll want to import the payments. The Squares Pay page has more on how to do that.
Server
Currently, squaresdb.mit.edu is the same VM as tech-squares-photos.mit.edu
To give somebody shell access, use "adduser $NEWUSER --disabled-password" to create an account for ssh pubkey access, and add a public key to ~/.ssh/authorized_keys. If they need to administer the server, either set a password and add them to the "admin" group so they can use sudo, or add them to root's authorized_keys.
If they should have readonly DB access, you can modify the Ansible script temporarily to create a MySQL user for them, and then run "GRANT squaresdb-ro TO $NEWUSER" to give them permissions.