[Nix-dev] Problem with grub

[Michael Raskin]

>Hi,
>
>my last update has messed up the grub configuration of one of my nixos machine.
>After boot, I get the grub console without any system ready to be launched.
>Now I don't know how to boot the system.
>
>I'm trying to use the rescue cd but I don't know exactly how to do.
>
>I can mount the disk and chroot in the system, but I don't know where to find /var/run/current-system etc.
>
>Any suggestion?

Yes, that is what I am ranting on #nixos the last week or so

The problem is GRUB update. What you need is a good recovery something 
with relatively fresh GRUB2 working. Most probably you can simply 
'set root=(hd?,?)' (I have no idea about your layout),  'linux /boot/nixos-kernel',
and 'initrd /nixos-initrd' (then 'boot').

I sneaked all that into default GRUB generator, so you have a good chance.

The problem is with GRUB detection of mount layout - http://savannah.gnu.org/bugs/?33263

Technically, you can boot, mount, chroot and use /nix/var/nix/profiles/system/ 
if you prefer.