devfs and unionfs oddity

Guy Helmer guy.helmer at
Thu Oct 27 16:05:01 UTC 2011

On a build server, I have a union mount of a FreeBSD o/s build from a point-in-time under a build directory, and then I have devfs mounted on dev in the build directory as well so I can do a chroot install of packages for particular target o/s versions.

mount shows this:
  <below>:/usr/app8xbuild/os-image on /usr/autobuild/images/product-image (unionfs, local)
  devfs on /usr/autobuild/images/product-image/dev (devfs, local, multilabel)

and the system does a chroot to /usr/autobuild/images/product-image/ while installing the ports for the product.

It seems impossible, but at times, after unmounting /usr/autobuild/images/product-image/dev and /usr/autobuild/images/product-image, a regular file /usr/autobuild/images/product-image/dev/null will be left as a result of redirecting some output to /dev/null during the port installs.

Could there be some odd interaction of devfs and unions that allows this to happen?

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