I recently discovered that on at least one of my Raspberry Pi’s docker was hanging on boot - for the order of 10 minutes or so. Manual attempts to start/restart docker hit the same issue.
I tracked down the apparent cause for the hang to this output from dmesg, which appeared immediately before docker (finally) started:
Mar 17 19:36:38 pi5 kernel: [ 692.320127] random: crng init done Mar 17 19:36:38 pi5 kernel: [ 692.320140] random: 7 urandom warning(s) missed due to ratelimiting
Turns out that the random number generator /dev/random was taking substantial time to gather enough entropy to properly initialize, and docker was waiting for /dev/random. The fix here was to install haveged which is a software random number generator, and which generates entropy for the system instead.
Haveged is installed by:
sudo apt install haveged
After installing haveged, on the next boot docker started in a much more timely fashion!comments powered by Disqus