/dev/bcache/by-uuid directory empty

[Nathan Dehnel]

I have modprobed bcache and registered the caches + backing drives
necessary to mount a volume on bcache:

root@guixrig ~/guix-configs/guixrig# ls /dev/bcache*
/dev/bcache0  /dev/bcache2  /dev/bcache4  /dev/bcache6  /dev/bcache8
/dev/bcache1  /dev/bcache3  /dev/bcache5  /dev/bcache7  /dev/bcache9

However, /dev/bcache/by-uuid is empty.
The manual https://www.kernel.org/doc/Documentation/bcache.txt states
that udev is necessary, and it is enabled:

root@guixrig ~/guix-configs/guixrig# herd status udev
Status of udev:
  It is started.
  Running value is 206.
  It is enabled.
  Provides (udev).
  Requires (root-file-system).
  Conflicts with ().
  Will not be respawned.

Is there something else I need to do to get the directory to populate?