$ sudo kyua debug -k /usr/tests/sys/fs/tmpfs/Kyuafile mknod_test:block | grep st_rdev
Files left in work directory after failure: mntpt, mounterr
st_rdev=8589934592
kyua: E: Removal of /tmp/kyua.Ry3oM8/2/work/mntpt failed: Device busy.x
$ sudo kyua debug -k /usr/tests/sys/fs/tmpfs/Kyuafile mknod_test:char | grep st_rdev
Files left in work directory after failure: mntpt, mounterr
st_rdev=8589934594
kyua: E: Removal of /tmp/kyua.1EaIdg/2/work/mntpt failed: Device busy.