tinyramfs/device-helper

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

create_symlink()
{
    sym="$1"
    sym="${sym%\"}"
    sym="${sym#\"}"
    sym="${dir}/${sym}"

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

# int main()
{
    [ "${dev_name=${DEVPATH##*/}}" ] || exit 1

    exec > /dev/null 2>&1

    # avoid race condition
    while ! blkid "/dev/${dev_name}"; do sleep 1; done

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

    [ -e "/sys/block/${dev_name}/dm/name" ] && {
        mkdir -p /dev/mapper
        read  -r dm_name < "/sys/block/${dev_name}/dm/name"
        ln    -sf "/dev/${dev_name}" "/dev/mapper/${dm_name}"
    }
}