I successfully booted my VM from network through PXE but I can't use my log in username and password to login. Also, it changed to ubuntu login to node login. What should I do?
Typically, you don't directly login to a node managed by MaaS. Instead, a tool like Juju (or some other program) connects to the MaaS interface and manages the machine for you, including worrying about what the login should be.
However, I believe if you go into the settings page in MaaS, you can set a SSH key for the machines to trust. You could tell it to trust the SSH key on your machine. You could then use that (along with the IP address listed for the node in the MaaS interface) to ssh to