Comment 35 for bug 1779827

According to this page

https://debianforum.de/forum/viewtopic.php?f=33&t=169585&hilit=entropie

This newly introduced fix in 4.15.0-24 is the cause

'random: fix crng_ready() test'

when it's reverted (like in debian 4.9.88-1+deb9u1) boot is fine again

'linux (4.9.88-1+deb9u1) stretch-security; urgency=high
[...]
  * Revert "random: fix crng_ready() test" (Closes: #897599), reopening
    CVE-2018-1108'

another solution could be to install 'haveged' as proposed and verified here

https://debianforum.de/forum/viewtopic.php?f=33&t=169585&hilit=entropie

and here

https://forum.ubuntuusers.de/topic/nix-geht-mehr-nach-installation-und-update/