(07-09-2020, 11:30 AM)illusive Wrote: If I had 4 PCs running X Windows, what’s the best way to logon to all 4 using one single sign-on?

I'm really not sure but I think you would have to use something like PAM or SSSD, if available on your platform, maybe along with a centralized authentication mechanism like Kerberos or LDAP.
I don't think any of the display managers currently support this out of the box.

If you're referring to graphical sessions, you'd have to launch each one on a different display and tty, so 4 in total. Which can be done with a simple script, maybe something using Xvnc and a swapping of display on every line.

I'm sure others might have more ideas about this than me though.