I got vncserver working per:

https://www.tecmint.com/install-and-configure-vnc-server-in-centos-7/

Then I went to set up a second instance, and have that for logging on to root:

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cp /lib/systemd/system/vncserver@.service /etc/systemd/system/vncserver@:2.service

vi /etc/systemd/system/vncserver@:2.service

replace <USER> with root

systemctl daemon-reload systemctl start vncserver@:2

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I got the message:

Job for vncserver@:2.service failed because a configured resource limit was exceeded. See "systemctl status vncserver@:2.service" and "journalctl -xe" for details.

#systemctl -l status vncserver@:2.service

● vncserver@:2.service - Remote desktop service (VNC)    Loaded: loaded (/etc/systemd/system/vncserver@:2.service; disabled; vendor preset: disabled)    Active: failed (Result: resources) since Wed 2018-08-01 08:45:19 EDT; 1min 8s ago   Process: 2267 ExecStart=/usr/sbin/runuser -l root -c /usr/bin/vncserver %i (code=exited, status=0/SUCCESS)   Process: 2260 ExecStartPre=/bin/sh -c /usr/bin/vncserver -kill %i > /dev/null 2>&1 || : (code=exited, status=0/SUCCESS)

Aug 01 08:45:14 localhost systemd[1]: Starting Remote desktop service (VNC)... Aug 01 08:45:19 localhost systemd[1]: PID file /home/root/.vnc/localhost:2.pid not readable (yet?) after start. Aug 01 08:45:19 localhost systemd[1]: Failed to start Remote desktop service (VNC). Aug 01 08:45:19 localhost systemd[1]: Unit vncserver@:2.service entered failed state. Aug 01 08:45:19 localhost systemd[1]: vncserver@:2.service failed.

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And yet, I am able to connect to 5902!  It is running.

cat /root/.vnc/localhost:2.log

shows:

Xvnc TigerVNC 1.8.0 - built Apr 11 2018 21:04:25 Copyright (C) 1999-2017 TigerVNC Team and many others (see README.txt) See http://www.tigervnc.org for information on TigerVNC. Underlying X server release 11903000, The X.Org Foundation

Wed Aug  1 08:45:16 2018  vncext:      VNC extension running!  vncext:      Listening for VNC connections on all interface(s), port 5902  vncext:      created VNC server for screen 0

Wed Aug  1 08:45:23 2018  ComparingUpdateTracker: 0 pixels in / 0 pixels out  ComparingUpdateTracker: (1:nan ratio)

Wed Aug  1 08:51:01 2018  Connections: accepted: 192.168.160.20::53318  SConnection: Client needs protocol version 3.8  SConnection: Client requests security type VeNCrypt(19)  SVeNCrypt:   Client requests security type TLSVnc (258)

etc.

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what is going on with systemctl?

thanks