They are typically created by:
mknod -m 660 /dev/hda b 3 0
mknod -m 660 /dev/hda1 b 3 1
mknod -m 660 /dev/hda2 b 3 2
...
mknod -m 660 /dev/hda8 b 3 8
mknod -m 660 /dev/hdb b 3 64
mknod -m 660 /dev/hdb1 b 3 65
mknod -m 660 /dev/hdb2 b 3 66
...
mknod -m 660 /dev/hdb8 b 3 72
chown root.disk /dev/hd*