Strangeness with /dev nodes and mknod

[Brian Candler]

I have a box running 6.0-STABLE as of 10 Nov last year.

Previously I had created device nodes for /dev/random within chroot
environments (this was for building and testing openssl). However now they
don't work. I am left with the strange situation that device nodes from
devfs work, but seemingly indentical device nodes created with mknod don't.

# dd if=/dev/random bs=1 count=8 | hexdump
8+0 records in
8+0 records out
8 bytes transferred in 0.000070 secs (114131 bytes/sec)
0000000 6eaf 1d71 513b 8d8c                    
0000008
# mknod /tmp/test1 c 0 24 root:wheel
# mknod /tmp/test2 c 24 0 root:wheel
# chmod 666 /tmp/test1 /tmp/test2
# ls -l /tmp/test1 /tmp/test2
crw-rw-rw-  1 root  wheel    0,  24 Mar 15 17:45 /tmp/test1
crw-rw-rw-  1 root  wheel   24,   0 Mar 15 17:45 /tmp/test2
# dd if=/tmp/test1 bs=1 count=8 | hexdump
dd: /tmp/test1: Operation not supported
# dd if=/tmp/test2 bs=1 count=8 | hexdump
dd: /tmp/test2: Operation not supported

Why do my lovingly hand-created device nodes fail with "Operation not
supported"?

Thanks,

Brian.