tinyramfs/device-helper

#!/bin/sh -f
#
# create /dev/disk/by-* and /dev/mapper/* symlinks

create_symlink()
{
    dir="$1"; sym="$2"

    sym="${sym%\"}"
    sym="${sym#\"}"
    sym="${dir}/${sym}"

    mkdir -p "$dir"
    ln    -s "../../${dev_name}" "$sym"
}

# DEVPATH is part of uevent which is exported to environment by device manager.
[ -b "/dev/${dev_name=${DEVPATH##*/}}" ] || exit 1

exec > /dev/null 2>&1

read -r dm_name < "/sys/block/${dev_name}/dm/name" && {
    mkdir -p /dev/mapper
    ln    -sf "../${dev_name}" "/dev/mapper/${dm_name:?}"
}

command -v blkid || exit 0

# Race condition may occur if uevent arrives faster(isn't that a kernel bug!?)
# than the kernel initializes device. This prevents blkid to fetch data from
# device. To fix this, we simply waiting until blkid is succeeded.
while ! _blkid=$(blkid "/dev/${dev_name}"); do
    if [ "$((count += 1))" = 30 ]; then
        exit 1
    else
        sleep 1
    fi
done

for line in $_blkid; do case                       "${line%%=*}" in
    UUID)     create_symlink /dev/disk/by-uuid     "${line##*=}" ;;
    LABEL)    create_symlink /dev/disk/by-label    "${line##*=}" ;;
    PARTUUID) create_symlink /dev/disk/by-partuuid "${line##*=}" ;;
esac; done