How to log into a remote ubuntu machine after it's reboot

To log in, ssh into the host like this:

ssh -l username ip address or the host name

so:
ssh -l MyUserName 255.255.255.255

then, type in

vncserver

it will give you something like
root@compname:~# vncserver

New 'X' desktop is compname:1

If the password doesn't work, remove the passwd files in the vnc folder of the remote computer:

rm .vnc/passwd

Then repeat the vncserver command; it'll ask for a password to be created so just type one in.