To add a user to the RAPI in Ganeti you need to do the following:
On any machine that has the openssl libraries, do the following:
# username: john
# password: p4ssw0rd
echo -n 'john:Ganeti Remote API:p4ssw0rd' | openssl md5
# copy the hash into /var/lib/ganeti/rapi/users like the following:
john {HA1}2f3ef95b86ddfd74c65c695f0efb7077 write
# for read-only access:
john {HA1}2f3ef95b86ddfd74c65c695f0efb7077