Not enough entropy to support /dev/random in docker containers running in boot2docker
Solution 1:
I just realized, that it is simple as mounting /dev/urandom from the host as /dev/random into the container:
$ docker run -v /dev/urandom:/dev/random ...
The result is as expected:
$ docker run --rm -it -v /dev/urandom:/dev/random ubuntu dd if=/dev/random of=/dev/null bs=1 count=1024
1024+0 records in
1024+0 records out
1024 bytes (1.0 kB) copied, 0.00223239 s, 459 kB/s
At least I know how to build my own boot2docker images now ;-)
Solution 2:
The most elegant solution I've found is running Haveged in separate container:
docker pull harbur/haveged
docker run --privileged -d harbur/haveged
Check whether enough entropy available:
$ cat /proc/sys/kernel/random/entropy_avail
2066
Solution 3:
Another option is to install the rng-tools package and map it to use the /dev/urandom
yum install rng-tools
rngd -r /dev/urandom
With this I didn't need to map any volume in the docker container.