Update README.md: Add --web=off for graphics

[Sangbaek]

Trouble

My machine prints out the following message when I executed the suggested command, docker run -it -v ${PWD}:/home/${USERNAME} -e DISPLAY=host.docker.internal:0 rootproject/root:latest root, under Enabling Graphics at README.md:

Find more info on https://root.cern/for_developers/root7/#rbrowser
Info in <THttpEngine::Create>: Starting HTTP server on port 127.0.0.1:9642

ROOT web-based widget started in the session where DISPLAY set to host.docker.internal:0
Means web browser will be displayed on remote X11 server which is usually very inefficient
One can start ROOT session in server mode like "root -b --web=server:8877" and forward http port to display node
Or one can use rootssh script to configure port forwarding and display web widgets automatically
Find more info on https://root.cern/for_developers/root7/#rbrowser
This message can be disabled by setting "WebGui.CheckRemoteDisplay: no" in .rootrc file
sh: 1: xdg-open: not found

Solution

This can be avoided by replacing root with bash -c 'root -l --web=off'.