I’ve found that with recent (1.6, 1.7) versions of Mozilla on Linux, you aren’t able to run multiple instances of the browser. If Mozilla is already running and you try to run Mozilla again, you get the Profile Manager which is a nuisance and of little use.

My solution was to write a shell script to determine if an instance is already running. If it is it opens a new window and if it isn’t, it runs mozilla normally. It’s quite simple but I thought it might come in handy for others, so here it is.

#!/bin/sh

# Run Mozilla normally if there are no other instances.  If there are, open
#   a new window within the running instance.

mozilla="/usr/local/mozilla/mozilla"

pgrep -f $mozilla 1> /dev/null 2>&1

if [ "$?" == 0 ]; then
    $mozilla -remote "openURL(about:blank, new-window)"
else
    $mozilla
fi

Make sure the path to mozilla is correct, and if you want to open a new tab instead of a new window, change new-window to new-tab.