https://unix.stackexchange.com/questions/346383/run-second-x-server-from-with...
privileges needed by X are ruled by systemd
$ sudo systemd-run --property PAMName=login --property User=user --property StandardInput=tty --property TTYPath=/dev/tty10 sh -c 'chvt 10 && startx /usr/bin/xterm -- :10'
Running as unit: run-r95a95f92511b45f2a9f135a40fb1f038.service
$ systemctl status run-r95a95f92511b45f2a9f135a40fb1f038.service
● run-r95a95f92511b45f2a9f135a40fb1f038.service - /bin/sh -c chvt 10 && startx /usr/bin/xterm -- :10
Loaded: loaded (/run/systemd/transient/run-r95a95f92511b45f2a9f135a40fb1f038.service; transient)
Transient: yes
Active: active (running) since Tue 2020-03-17 08:11:34 MSK; 17s ago
Main PID: 21859 ((sh))
Tasks: 1 (limit: 4915)
Memory: 160.0K
CPU: 1ms
CGroup: /system.slice/run-r95a95f92511b45f2a9f135a40fb1f038.service
└─21859 (sh)
Mar 17 08:11:34 sabayon.local systemd[1]: Started /bin/sh -c chvt 10 && startx /usr/bin/xterm -- :10.
но сервер-то не запускается (и логфайл /var/log/Xorg.10.log не создаётся)!
Ну и мне надо при старте системы, а не из командной строки.