1. Make required directories mkdir -p /userdata/mergerfs/VERSION_NUMBER && cd /userdata/mergerfs/VERSION_NUMBER

  2. Download newest static mergerfs build, current built now can be found HERE

  3. extract tar -xvzf FLIE_NAME.tgz

  4. cd ../ && ln -s VERSION_NUMBER current

  5. Create disk labels so we know what to add to the script, replace LABEL_NAME and /dev/sda1 with your disk info e2label LABEL_NAME /dev/sda1. Thankfully batocera mounts disks by label in the /media/ folder

  6. Create script to mount nano mergerfs.sh

#!/bin/bash

/userdata/mergerfs/current/usr/local/bin/mergerfs -o defaults,allow_other /media/HDD1:/media/HDD2:/media/HDD3 /userdata/roms
  1. Add script to batocera-boot file. Add sharenetwork_cmd2=bash /userdata/mergerfs/mergerfs.sh to /boot/batocera-boot.conf and switch sharedevice=INTERNAL to sharedevice=DEVICES