[Nix-dev] NixOS hangs on boot after upgrading 15.09 -> 16.03; systemd update to blame?

[James Cook]

On 22 June 2016 at 19:27, James Cook <james.cook at utoronto.ca> wrote:
> After updating my desktop from 15.09 to 16.03, it hangs on boot after
> printing the message "regenerating udev hardware database". I do not
> think the problem is directly related to that message; see below. Any
> ideas for debugging this?
>
> Here's what I've figured out so far:
>
> * Using git-bisect, it seems that the problem starts at commit
> ecbe04b4, "systemd: Update to 225". (I had to cherry-pick 3cc04956,
> "libseccomp: Fix hash", to got it to build.)
>
> * I don't think the script that prints "regenerating udev hardware
> database" is the one that hangs. I added a debugging echo command to
> the end of system.activationScripts.udevd (in
> nixos/modules/services/hardware/udev.nix), and I saw the extra message
> when I booted. So the hang happens after.
>
> My next step was going to be to add more debugging statements to the
> boot process, but I'm having trouble figuring out where any of that
> stuff is. I can't find where system.activationScripts.udevd is called
> from, and I was mystified to find that grep -R "egenerating udev"
> /nix/store/(...)-nixos-16.0.3.git.3cc0495M produces no output (except
> some errors, e.g. etc/zoneinfo/posix is a directoly loop).
>
> James

Another note: the problem also happens on master (commit 0167eef9).
The "regenerating udev hardware database..." message is no longer
printed at master; the last messages before the hang are "setting up
/etc..." and a bunch of "removing obsolete symblink ..." and "removing
group ..." messages.

James