nerves_system_openwrt_one

#!/bin/sh
#
# Mount /root (= /data via symlink, Nerves convention) from UBI
# volume 5 (rootfs_data). Lazily formats the volume with UBIFS on
# first boot or after corruption. Falls back to tmpfs if the
# persistent mount can't be brought up, so the system always boots
# even if NAND is unhealthy.
#
# Run via erlinit's --pre-run-exec, before the Erlang VM starts.
#

set -u

PATH=/usr/sbin:/usr/bin:/sbin:/bin
export PATH

DATA_DEV=/dev/ubi0_5
DATA_MNT=/root
MOUNT=/bin/mount
MKFS_UBIFS=/usr/sbin/mkfs.ubifs

mkdir -p "$DATA_MNT"

# Already mounted from a prior invocation? (e.g., supervised respawn)
if grep -q " $DATA_MNT " /proc/mounts; then
    exit 0
fi

if [ ! -c "$DATA_DEV" ]; then
    echo "mount-data: $DATA_DEV is not a UBI volume; using tmpfs at $DATA_MNT" >&2
    "$MOUNT" -t tmpfs tmpfs "$DATA_MNT"
    exit 0
fi

# First try mounting. If the volume already has a UBIFS, this just works.
if "$MOUNT" -t ubifs "$DATA_DEV" "$DATA_MNT" 2>/dev/null; then
    exit 0
fi

# Mount failed — assume the volume is empty/corrupt and reformat.
echo "mount-data: formatting $DATA_DEV with UBIFS" >&2
if "$MKFS_UBIFS" -y -q "$DATA_DEV" \
        && "$MOUNT" -t ubifs "$DATA_DEV" "$DATA_MNT" 2>/dev/null; then
    exit 0
fi

echo "mount-data: persistent mount failed; falling back to tmpfs at $DATA_MNT" >&2
"$MOUNT" -t tmpfs tmpfs "$DATA_MNT"