In most cases, using a second USB hard drive to host your ROMs separately from the Batocera system should be totally transparent when you use the dedicated menu item to enable it.
However, when tinkering with the systems, things can go wrong. This page is here to help you troubleshoot and fix those cases.
Say you are running Batocera off a USB pendrive (or SD card) but want to host your ROM files on a different hard drive. In that case, you need to edit
/boot/batocera-boot.conf and provide the information of the hard drive that hosts your ROMs. In order to do that, you can list the UUID of the drive that hosts the ROMs by typing the
/dev/sdb2: LABEL="SHARE" UUID="12e46ca9-xxxx-xxxx-xxxx-xxxxxxxxxx" TYPE="ext4" /dev/sdb1: LABEL="BATOCERA" UUID="zzzz-zzzz" TYPE="vfat" /dev/sda1: LABEL="SHARE" UUID="2efa1068-yyyy-yyyy-yyyy-yyyyyyyyyy" TYPE="ext4"
In that example,
/dev/sdb1 is my Batocera boot partition,
/dev/sdb2 is the rest of my Batocera USB pendrive (that I don't want to use) and
/dev/sda1 if the partition hosting my ROM files. In order to use that partition, I need to edit
/boot/batocera-boot.conf and put:
# device to the share data (userdata) sharedevice=DEV 2efa1068-yyyy-yyyy-yyyy-yyyyyyyyyy # disable the splashsound (remove the # to disable sound) #splashsound=false # enable the nvidia driver (remove the # to enable it) #nvidia-driver=true