How to launch a new instance of Google Chrome from the command line?

This is a known bug. A workaround posted there is to pass the argument --user-data-dir=/tmp (with a temporary or empty directory) to start a new session.

I do this

cd ~/.config/google-chrome
mkdir /tmp/chrome2
find . -print | cpio -mpdv /tmp/chrome2 # there was no cp -R in my day!
rm -fr /tmp/chrome2/Singleton*
rm -fr /tmp/chrome2/Session* 
google-chrome --user-data-dir=/tmp/chrome2/

Instead of the cpio/rm lines I'm using this now

rsync -av --delete --exclude=/Singleton* --exclude=/Session* ~/.config/google-chrome/ /tmp/chrome2/