john_alan
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Joined: Mon Jul 22, 2019 7:20 pm

Entropy of headless setup

Fri Jan 10, 2020 11:27 am

Is the entropy of a headless raspberry pi setup considered OK despite having no keyboard/mouse, given that the pi boasts a Hardware TRNG?

epoch1970
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Re: Entropy of headless setup

Fri Jan 10, 2020 9:08 pm

If by "OK" you mean "works" then yes it does work. Raspbian Lite (others?) comes preinstalled with rngd or haveged, I don't remember having seen processes fail or block waiting for entropy.
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

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HawaiianPi
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Location: Aloha, Oregon USA

Re: Entropy of headless setup

Fri Jan 10, 2020 9:17 pm

Depends in which version of Raspbian. Older versions didn't include rng-tools by default, more recent ones do.

Code: Select all

apt policy rng-tools
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jahboater
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Re: Entropy of headless setup

Fri Jan 10, 2020 10:10 pm

epoch1970 wrote:
Fri Jan 10, 2020 9:08 pm
If by "OK" you mean "works" then yes it does work. Raspbian Lite (others?) comes preinstalled with rngd or haveged, I don't remember having seen processes fail or block waiting for entropy.
Isn't some entropy saved to disk so that its available immediately on boot up?

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HawaiianPi
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Re: Entropy of headless setup

Fri Jan 10, 2020 10:20 pm

jahboater wrote:
Fri Jan 10, 2020 10:10 pm
Isn't some entropy saved to disk so that its available immediately on boot up?
Don't know about that, but there used to be a problem with headless VNC taking a long time to reconnect after a reboot (due to lack of entropy), and installing haveged or rng-tools seemed to fix it. Because of that, the Raspbian devs started including rng-tools by default in some version of Stretch (don't recall exactly when). So later versions of Stretch and all versions of Buster should have it.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

trejan
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Joined: Tue Jul 02, 2019 2:28 pm

Re: Entropy of headless setup

Fri Jan 10, 2020 11:49 pm

IIRC it also caused problems with the SSH host key generation at first boot which took a long time. If people were impatient and pulled power because it appeared to be dead then they could end up with the keys half generated. The SSH server wouldn't work but it also wouldn't regenerate the keys.

john_alan
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Joined: Mon Jul 22, 2019 7:20 pm

Re: Entropy of headless setup

Sat Jan 11, 2020 9:57 am

Thanks folks sounds good.

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