I'm designing a minimal custom Buildroot embedded OS for the RPi0w. My current iteration takes a very long time to fully boot - several minutes with a keyboard and mouse plugged in, and tens of minutes with no input devices. It hangs for a long time and then finally outputs the message:

random: crng init done

It's an embedded system with no sound-card or input devices so I presume that the random number generator is starved for entropy - it has to wait a long time to get enough noise before it will initialise.

I would like to install rng-tools to provide the extra entropy required, but I'm not sure how to configure it in Buildroot.

Looking for someone who has done this before in Buildroot who can offer assistance on what configuration files are necessary, how/when to start rngd (I'm using plain /etc/init.d scripts), what kernel modules need to be loaded to use the Raspberry Pi's builtin random generator, etc.

1 Answer 1


Simply selecting rng-tools (under Target Packages -> Hardware Handling in the Buildroot menuconfig) and running make completely fixed the problem. Buildroot automatically added a S21rngd in /etc/init.d/. My system now starts up in about 4 seconds with no input devices attached.

  • This answer has just saved me from descending into insanity. Jan 11, 2022 at 14:58
  • The stakes are high in this industry Feb 2, 2022 at 23:59

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