Create the backing files for the USB drives on a separate partition.

windows_archive/create-backingfiles.sh

@@ -0,0 +1,37 @@
+#!/bin/bash -eu
+
+SPACE_TO_USE="$1"
+CAM_PERCENT="$2"
+BACKINGFILES_MOUNTPOINT="$3"
+
+G_MASS_STORAGE_CONF_FILE_NAME=/etc/modprobe.d/g_mass_storage.conf
+
+function add_drive () {
+  local name="$1"
+  local label="$2"
+  local size="$3"
+
+  local filename="$4"
+  fallocate -l "$size"K "$filename"
+  mkfs.vfat "$filename" -F 32 -n "$label"
+
+  local mountpoint=/mnt/"$name"
+
+  mkdir "$mountpoint"
+  echo "$filename $mountpoint vfat noauto,users,umask=000 0 0" >> /etc/fstab
+}
+
+CAM_DISK_SIZE="$(( $SPACE_TO_USE * $CAM_PERCENT / 100 ))"
+CAM_DISK_FILE_NAME="$BACKINGFILES_MOUNTPOINT/cam_disk.bin"
+add_drive "cam" "CAM" "$CAM_DISK_SIZE" "$CAM_DISK_FILE_NAME"
+
+if [ "$CAM_PERCENT" -lt 100 ]
+then
+  MUSIC_PERCENT="$(( 100 - $CAM_PERCENT ))"
+  MUSIC_DISK_SIZE="$(( $SPACE_TO_USE * $MUSIC_PERCENT / 100 ))"
+  MUSIC_DISK_FILE_NAME="$BACKINGFILES_MOUNTPOINT/music_disk.bin"
+  add_drive "music" "MUSIC" "$MUSIC_DISK_SIZE" "$MUSIC_DISK_FILE_NAME"
+  echo "options g_mass_storage file=$CAM_DISK_FILE_NAME,$MUSIC_DISK_FILE_NAME removable=1,1 ro=0,0 stall=0 iSerialNumber=123456" > G_MASS_STORAGE_CONF_FILE_NAME
+else
+  echo "options g_mass_storage file=$CAM_DISK_FILE_NAME removable=1 ro=0 stall=0 iSerialNumber=123456" > G_MASS_STORAGE_CONF_FILE_NAME
+fi