rng failure

[Joe Long]

the strong random number generator is not working on one of our HP-UX 11i servers following a reboot. Attempts to get random numbers from/dev/urandom fails. For example, if I do "cat /dev/urandom" instead of a string of random characters I get the error message "Cat: Cannon open /dev/urandom: Invalid argument" I have unloaded and reloaded the rng module to no effect.

This is the output from kmadmin -Q rng:

Module Name rng
Module ID 2
Module Path /stand/dlkm/mod.d/rng
Status LOADED
Size 57344
Base Address 0x178e000
BSS Size 0
BSS Base Address 0x0
Hold Count 1
Dependent Count 0
Unload Delay 0 seconds
Description rng - random number generator for the /dev/[u]random interface
Type WSIO
Block Major -1
Character Major 95
Flags b5

Any suggestions?

[Navin Bhat_2]

Are there any errors reported in the swagent.log file? Also are you getting the same error with /dev/random?

[Navin Bhat_2]

Also try to tusc the cat aommand maybe we can see something useful there.

[Joe Long]

I get a somewhat different error with /dev/random:

jlong@bp-prod: /home/jlong # cat /dev/random > random.txt
cat: read error: No such file or directory

However, the directory is there:

jlong@bp-prod: /home/jlong # ll /dev/random
cr--r--r-- 1 bin bin 79 0x000000 Aug 27 2003 /dev/random

But I believe your suggestion of checking the swagent.log provided the answer. The depot I installed at the time of the reboot recreated the rng module. I have another maintenance window coming up, and I'll remove and reinstall the KRMG11i depot and see if that corrects the problem. Thanks.

[A. Clay Stephenson · Accepted solution]

I see what is wrong. You kmadmin -Q rng reports a Character Major device number of 95 but your /dev/urandom and /dev/random have a major device number of 79.

rm /dev/random
rm /dev/urandom

mknod /dev/random c 95 0x00
mknod /dev/random c 95 0x01

You can also simply cd to /sbin/init.d and
./krng stop
./krng start

By the way, these devices do not produce random strings but rather random binary data so you might want to do something like this:

dd if=/dev/random bs=4 count=1 | od -c

[Joe Long]

That did it ... thank you.

[A. Clay Stephenson]

Ooops,

I just noticed that
mknod /dev/random c 95 0x01

should be:
mknod /dev/urandom c 95 0x01

but you probably spotted that. The other mknod was correct.