Share Firefox profile between two Linux machines without Firefox Sync

firefox-and-push-mozilla.sh

#!/usr/bin/env bash

"$@"

if [[ $HOSTNAME != "ra" ]]; then
	push-mozilla
fi

firefox.sh

#!/usr/bin/env bash

# The design here does not involve NFS, but ra is still treated as a master from
# which plato "checks out" ~/.mozilla and rsyncs it back as soon as Firefox exits.

set -eu -o pipefail

. ~/bin/fix-env-vars

# Enable high-resolution touchpad scroll, which Firefox 70 still doesn't enable
# by default.
export MOZ_USE_XINPUT2=1

firefox=/run/current-system/sw/bin/firefox
profile=$HOME/.mozilla/firefox/aaaaaaaa.default

# if Firefox is already running, don't do any of the profile management below
if pgrep firefox; then
	exec "$firefox" "$@"
fi

# Shoot down the Firefox running on the other computer
if [[ $HOSTNAME == "ra" ]]; then
	# plato will rsync over its profile back to ra when firefox exits, so we
	# need to run quit-firefox on plato and wait for the profile to arrive.
	#
	# plato may be down, so use the first ssh to probe whether machine is up.
	# This avoids applying a short timeout to the quit-firefox, which may take
	# longer.
	(timeout 3 ssh at@plato echo && ssh at@plato "~/bin/quit-firefox") || true
else
	ssh at@ra "~/bin/quit-firefox"

	# back up profile
	rm -rf ~/trash/.mozilla
	cp -al ~/.mozilla ~/trash/
	# "check out" the profile from ra
	pull-mozilla
fi

# Manage devPixelsPerPx manually because Firefox doesn't get it right
pixelsperpx=1.0
if [[ $HOSTNAME = "ra" ]]; then
	pixelsperpx=1.7
fi

for prefs in "$profile"/prefs.js; do
	echo "Fixing $prefs"
	sed -i -r "s/user_pref\(\"layout\.css\.devPixelsPerPx\", \".+\"\);/user_pref(\"layout.css.devPixelsPerPx\", \"$pixelsperpx\");/g" "$prefs"
done

exec ~/bin/firefox-and-push-mozilla "$firefox" "$@"

fix-env-vars.sh

#!/usr/bin/env bash

panel_environ() {
	cat "/proc/$(pgrep -u "$(whoami)" xfce4-panel)/environ" | tr '\0' '\n'
}

export DISPLAY=$(                 panel_environ | grep '^DISPLAY='                  | sed -r 's,^[^=]+=,,g')
export XAUTHORITY=$(              panel_environ | grep '^XAUTHORITY='               | sed -r 's,^[^=]+=,,g')
export DBUS_SESSION_BUS_ADDRESS=$(panel_environ | grep '^DBUS_SESSION_BUS_ADDRESS=' | sed -r 's,^[^=]+=,,g')
export XDG_CURRENT_DESKTOP=$(     panel_environ | grep '^XDG_CURRENT_DESKTOP='      | sed -r 's,^[^=]+=,,g')
export XDG_SESSION_ID=$(          panel_environ | grep '^XDG_SESSION_ID='           | sed -r 's,^[^=]+=,,g')
export XDG_SEAT=$(                panel_environ | grep '^XDG_SEAT='                 | sed -r 's,^[^=]+=,,g')
export XDG_RUNTIME_DIR=$(         panel_environ | grep '^XDG_RUNTIME_DIR='          | sed -r 's,^[^=]+=,,g')
export SHELL_SESSION_ID=$(        panel_environ | grep '^SHELL_SESSION_ID='         | sed -r 's,^[^=]+=,,g')
export SESSION_MANAGER=$(         panel_environ | grep '^SESSION_MANAGER='          | sed -r 's,^[^=]+=,,g')

pull-mozilla.sh

#!/bin/sh

set -e

rsync -avX --delete at@ra:.mozilla ~/

push-mozilla.sh

#!/bin/sh

set -e

rsync -avX --delete ~/.mozilla at@ra:

quit-firefox.sh

#!/usr/bin/env bash

enable -f /run/current-system/sw/lib/bash/sleep sleep

. ~/bin/fix-env-vars

windows=$(wmctrl -l | grep -P ' Mozilla Firefox$' | cut -f 1 -d ' ')
for window in $windows; do
	wmctrl -i -c "$window"
done

while pgrep -f firefox-and-push-mozilla; do
	sleep 0.05
done