can't open /dev/hwrng: No such device - but it exists!

We are very low on entropy (HTTPS apache server, Ubuntu 12.04, not a VM, HW: using a Lenovo ThinkCentre M58):

root@server:~# cat /proc/sys/kernel/random/entropy_avail
417
root@server:~# 

We need more randomness, so:

root@server:~# apt-get install rng-tools
... ok!

but when starting:

root@server:~# service rng-tools start
Starting Hardware RNG entropy gatherer daemon: (failed).
root@server:~# 

The config is the default:

root@server:~# egrep -v '^$|^#' /etc/default/rng-tools
root@server:~# 

trying with hand:

root@server:~# /usr/sbin/rngd
can't open /dev/hwrng: No such device
root@server:~# 

The 11:29 was when we installed rng-tools:

root@server:~# ls -lah /dev/hwrng
crw------- 1 root root 10, 183 jan 6 11:29 /dev/hwrng
root@server:~# 

Trying strace:

root@server:# strace /usr/sbin/rngd 2>&1 | grep hwrng
open("/dev/hwrng", O_RDONLY|O_LARGEFILE) = -1 ENODEV (No such device)
write(2, "can't open /dev/hwrng: No such d"..., 37can't open /dev/hwrng: No such device) = 37
root@server:# 

Question: how to get "/dev/hwrng" to work with rngd? Or is our hardware bad? Or missing some BIOS settings? How to resolve/check it without downtime?

1 Answer

apt-get install haveged

and:

user@server:~$ cat /proc/sys/kernel/random/entropy_avail
2417
user@server:~$