Yes, you can copy a
/dev/random device. If the Linux filesystem you're taking them from has compatible definitions (same major and minor numbers), which it should, it will work.
You can't just use
cp with no arguments, because that copies the random data and not the filesystem object. Use
cp -a. (
-a is the GNU option for "preserve everything").
Secondly, of course you have to be root, which it can be assumed you are if you're trying to create a
/dev entry. If a regular user tries
cp -a /dev/random foo, they are greeted with:
cp: cannot create special file `foo': Operation not permitted
If you have the permissions,
cp -a it will create a duplicate of the special (character device) file.
Another way is just mknod. If we happen to know that the device major number for
random is 1, and the minor number is 8, we can do
mknod foo c 1 8 # character device, major 1, minor 8
foo points to the same kernel device as
/dev/random. Permissions are important also; when creating
/dev entries, watch the perms; use the
-m argument of
/dev/random from an existing Linux filesystem tree with
cp -a, it should hopefully have the right permissions (and of course ownership) already.
However, I would investigate why your system doesn't have these entries!