docker-plex/root/etc/cont-init.d/50-plex-update

#!/usr/bin/with-contenv bash

# copy config on first run, regardless of update status
[[ ! -e /etc/default/plexmediaserver ]] && \
	cp /defaults/plexmediaserver /etc/default/plexmediaserver

# set no update message
[[ -e /tmp/no-version.nfo ]] && \
	rm /tmp/no-version.nfo
NOVERSION_SET='/tmp/no-version.nfo'
cat > "${NOVERSION_SET}" <<-EOFVERSION


#######################################################
# Update routine will not run because you havent set  #
# the VERSION variable, for more information checkout #
#    https://github.com/linuxserver/docker-plex       #
#######################################################
EOFVERSION

# test for no version set or opt out for autoupdates
if [[ -z "$VERSION" ]] || [[ "$VERSION" == "0" ]] || [[ ! -z "$ADVANCED_DISABLEUPDATES" ]]; then
printf "%s\n\n\n" "$(</tmp/no-version.nfo)"
exit 0
fi

# set header for no preferences/token message
[[ -e /tmp/no-token.nfo ]] && \
	rm /tmp/no-token.nfo
NOTOKEN_SET='/tmp/no-token.nfo'
cat > "${NOTOKEN_SET}" <<-EOFTOKEN


#####################################################
#   Login via the webui at http://<ip>:32400/web    #
#   and restart the docker, because there was no    #
EOFTOKEN

# if preferences files doesn't exist, exit out
if [ ! -e "/config/Library/Application Support/Plex Media Server/Preferences.xml" ]; then
cat >> "${NOTOKEN_SET}" <<-EOFTOKEN
#   preference file found, possibly first startup.  #
#####################################################
EOFTOKEN
printf "%s\n\n\n" "$(</tmp/no-token.nfo)"
exit 0
fi

# attempt to read plex token
PLEX_TOKEN=$( sed -n 's/.*PlexOnlineToken="//p' \
	"/config/Library/Application Support/Plex Media Server/Preferences.xml" \
	| sed "s/\".*//")

# if plex token isn't found, exit out
if [ -z "$PLEX_TOKEN" ]; then
cat >> "${NOTOKEN_SET}" <<-EOFTOKEN
#      plex token found in the preference file      #
#####################################################
EOFTOKEN
printf "%s\n\n\n" "$(</tmp/no-token.nfo)"
exit 0
fi

# determine installed version of plex
INSTALLED=$(dpkg-query -W -f='${Version}' plexmediaserver)

# start update routine
if [[ "$VERSION" = latest ]] || [[ "$VERSION" = plexpass ]] || [[ "$PLEXPASS" == "1" ]]; then
PLEX_TOKEN="${PLEX_TOKEN}"
else
PLEX_TOKEN=""
fi
VERSION=$(curl -s "https://plex.tv/downloads/latest/1?channel=8&build=linux-ubuntu-x86_64&distro=ubuntu&X-Plex-Token=$PLEX_TOKEN"| cut -d "/" -f 5 )

if [[ "$VERSION" == "$INSTALLED" ]]; then
echo "No update required"
exit 0
fi

echo "Atempting to upgrade to: $VERSION"
last=130
while [[ $last -ne "0" ]]; do
	rm -f /tmp/plexmediaserver_*.deb
	curl -o /tmp/plexmediaserver_"${VERSION}"_amd64.deb -L \
		"${PLEX_URL}/plex-media-server/$VERSION/plexmediaserver_${VERSION}_amd64.deb"
	last=$?
done
 apt-get remove --purge -y \
	plexmediaserver
dpkg -i /tmp/plexmediaserver_"${VERSION}"_amd64.deb
rm -f /tmp/plexmediaserver_*.deb

# recopy config file in case update overwrites our copy
cp -v /defaults/plexmediaserver /etc/default/plexmediaserver