To run a command in a new or existing virtual terminal, try
openvt. I don’t know what exactly you mean with “during boot”, but perhaps systemd’s rc-local.service is your solution.
To switch between ssh sessions: If the local shell has job control, you can suspend the current shell session with the two-key sequence
tilde ctl-z. To resume a suspended ssh session, list all suspended jobs with the
jobs command, then
fg %N to resume job number N.
You could also run each ssh in a
screen then use
ctl-a d to leave a screen.
Or if you have a GUI, simply run each ssh in a separate window and switch windows.
