tree 150d5c02956398f949c725e55c949b6105f76da8
parent ea098db319e200f1a9570ecec3a9beb90453151d
author Jan Kundrát <kundrat@cesnet.cz> 1551888088 +0100
committer Jan Kundrát <kundrat@cesnet.cz> 1551888088 +0100

Preserve random seed across reboots

At first I tried to just use systemd's systemd-random-seed, but that one
does not actually use an appropriate ioctl for persuading kernel that
entropy is there. There's a patch [1] for this, but its fate is far from
certain, and even with it, I am not completely sure that I got
everything working correctly (some boots were quick, others waited for
systemd-resolved in the same manner as before this patch).

In the end, just seeding stuff from the initrd [2] is much easier. A
downside is that the systemd unit systemd-random-seed.service will add
the contents of that file once again -- but that doesn't matter much
because we do not patch it, and therefore it does not increase kernel's
idea about available entropy.

Changes from that upstream rndaddentropy:

- larger buffer
- more conservative entropy contribution

[1] https://github.com/systemd/systemd/pull/10621 .
[2] https://github.com/rfinnie/twuewand/blob/master/rndaddentropy/rndaddentropy.c

Change-Id: Ibe3c926c241d75fb7d7c40f3df2a96813931971b