Very slow boot and sluggish when SERVER changes 4.9 to 4.19

I'm running a Devuan LTSP server and chroot. Chroot is Devuan Beowulf 
(Debian Buster) fully up to date and works fine with kernel v4.19. I've 
recently updated the server from Ascii (Stretch) to Beowulf. I updated 
all the elements *except* the kernel on the server (with reboots 
inbetween) and LTSP clients were fine. When I update the server kernel 
from 4.9 to 4.19 I get a very slow client boot and sluggish clients. The 
only difference is the server kernel as I can rollback / forward and see 
the difference.

(Hopefully) relevant extract from dmesg on the client:

[    6.277875] FS-Cache: Netfs 'nfs' registered for caching
[    6.977754] random: fast init done
[   13.343880] urandom_read: 1 callbacks suppressed
[   13.343882] random: mktemp: uninitialized urandom read (10 bytes read)
[   73.909618] udevd[561]: starting version 3.2.7
[   74.052792] random: udevd: uninitialized urandom read (16 bytes read)
[   74.058644] random: udevd: uninitialized urandom read (16 bytes read)
[   74.058668] random: udevd: uninitialized urandom read (16 bytes read)
[   74.079290] udevd[561]: specified group 'kvm' unknown
[   74.241951] udevd[561]: starting eudev-3.2.7

Whereas the previous one would take about 8secs and then all progress fine.

I guess my first question/confusion is why a change of the *server* 
kernel has an impact when I'm running a chroot that has not changed it's 
kernel?

And turning to the problem itself. It looks likes random generation is 
taking a long time - which I think occurred somewhere about kernel 4.14 
from a quick look on searching for non-LTSP but similar-ish embedded errors.

Is there a way I can fake / preload the random generation? Given it's 
for a home setup then I would probably be happy to trade local security 
on the internal network of my LTSP clients unless someone tells me why 
that's a bad idea.

And I'm not sure why this then persists into a sluggish LTSP client 
session. Possibly a second issue?

Thanks,
Nick.




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