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Re: fix for no ssh



On 2019-07-07, Andrei POPESCU <andreimpopescu@gmail.com> wrote:

> 
> It sounds a lot like this issue:
> https://www.debian.org/releases/buster/amd64/release-notes/ch-information.en.html#entropy-starvation

 Due to systemd needing entropy during boot and the kernel treating such calls
 as blocking when available entropy is low, the system may hang for minutes to
 hours until the randomness subsystem is sufficiently initialized (random: crng
 init done). For amd64 systems supporting the RDRAND instruction this issue is
 avoided by the Debian kernel using this instruction by default
(CONFIG_RANDOM_TRUST_CPU).

For amd64 systems with the RDRAND instruction, the euphemistically termed
"issue" (hanging for minutes or hours!) is "avoided." 

That avoidance is wonderful news for me, as I happen to have an amd64 system
myself. But does it support the RDRAND instruction? How do I find out? What do
I do if it doesn't? Here the notes suffer from a maddening silence.

At any rate, I case-insensitively grepped for the RDRAND flag in /proc/cpuinfo
and came up with nada (this is a pretty old machine), if that is indeed how you
discover whether you have the instruction or not.

But now I'm uncertain whether this bug will affect me or not.

https://daniel-lange.com/archives/152-Openssh-taking-minutes-to-become-available,-booting-takes-half-an-hour-...-because-your-server-waits-for-a-few-bytes-of-randomness.html

https://lists.debian.org/debian-devel/2018/12/msg00184.html

I guess I would not be affected because I'm not running an entropy-hungry
service (or any services at all), but what a PITA to have gone on this wild
goose chase to finally find that out (if true). These release-notes for Buster,
as they stand, are apparently both wrong (migration of interface names) and
misleading (if the entropy-starvation stanza had begun, "For those running
services using the  getrandom() system call..." or something, I probably
wouldn't be here cluttering the forum with my bullshit).

> Kind regards, Andrei



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