Stories
Slash Boxes
Comments

SoylentNews is people

Post-Boot Delays in SSH Access Due to Small Entropy Pool

posted by Fnord666 on Friday December 21 2018, @06:19PM   Printer-friendly
from the chaos-monkey dept.

canopic jug writes:

Recent upgrades that depend on the new Linux getrandom() syscall can cause OpenSSH to delay starting for tens of minutes while waiting for enough bytes of randomness. There are currently not any feasible work-arounds.

Systemd makes this behaviour worse, see issue #4271, #4513 and #10621.
Basically as of now the entropy file saved as /var/lib/systemd/random-seed will not - drumroll - add entropy to the random pool when played back during boot. Actually it will. It will just not be accounted for. So Linux doesn't know. And continues blocking getrandom(). This is obviously different from SysVinit times when /var/lib/urandom/random-seed (that you still have laying around on updated systems) made sure the system carried enough entropy over reboot to continue working right after enough of the system was booted.

#4167 is a re-opened discussion about systemd eating randomness early at boot (hashmaps in PID 0...). Some Debian folks participate in the recent discussion and it is worth reading if you want to learn about the mess that booting a Linux system has become.

While we're talking systemd ... #10676 also means systems will use RDRAND in the future despite Ted Ts'o's warning on RDRAND [Archive.org mirror and mirrored locally as 130905_Ted_Tso_on_RDRAND.pdf, 205kB as Google+ will be discontinued in April 2019].

Related post: OneRNG: a Fully-Open Entropy Generator (2014)

Original Submission

 
This discussion has been archived. No new comments can be posted.
Post-Boot Delays in SSH Access Due to Small Entropy Pool | Log In/Create an Account | Top | 69 comments | Search Discussion
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.

  • (Score: 0) by Anonymous Coward on Saturday December 22 2018, @08:09PM

    by Anonymous Coward on Saturday December 22 2018, @08:09PM (#777636)

    I haven't had any issues like that on my thinkpad or my macbook air, both running linux with no DE at all just running straight wpa_supplicant. If I move to a different wifi location, it connects to the new AP as long as it's configured. If it doesn't for some reason, the most I've had to do is restart the service (which is just a sysvinit script that disables the interface, re-enables, and reconnects using wpa_supplicant and dhcpcd). The order that the AP's are listed in the conf is the order of precedence, so if I'm connected to my phone's hotspot and come into range of my home AP, it connects to the home wifi instead.
    OpenBSD requires re-running the /etc/netstart script though.
    Is your wifi card really obscure with a horrible driver or something?