dracut/modules.d/95rootfs-block/block-genrules.sh

#!/bin/sh

if [ "${root%%:*}" = "block" ]; then
    {
        printf 'KERNEL=="%s", SYMLINK+="root"\n' \
            ${root#block:/dev/}
        printf 'SYMLINK=="%s", SYMLINK+="root"\n' \
            ${root#block:/dev/}
    } >> /etc/udev/rules.d/99-root.rules

    printf '[ -e "%s" ] && { ln -s "%s" /dev/root 2>/dev/null; rm "$job"; }\n' \
        "${root#block:}" "${root#block:}" > $hookdir/initqueue/settled/blocksymlink.sh

    wait_for_dev "${root#block:}"
fi