Hosting providers & NixOS
NixOS is using very recent software & kernels by default. If you try to install NixOS on virtualizing systems be prepared that you have to patch some libraries to make them work with older kernels.
 Hosting providers known to run NixOS
- Rob Vermaas and Marc Weber are running NixOS on linode.com - see Install NixOS on Linode.
- Starting from january 2013 netcup provides KVM servers. Installing NixOS works without problems, since you are able able to run your own kernel and upload ISOs to boot from.
- KVM hosting with custom ISO images on http://www.supremebytes.com/business-virtual-servers.php
 NixOs experiences about other providers
Support let's you use your init if you ask them. But Upstart is causing trouble. It dosn't recognize when jobs have finished or started. Thus you don't pass the start script. So you don't even start sshd. Thu Dec 17 2009: upstart-0.6.3 doesn't work either.(Outdated)
If you remove /bin/cp your data is lost. Older but probably very stable kernels. I got a stystem running using some kind of bind mound magic keeping the original debian in place. However I gave up updating it. It's still running my irssi client and hosting my .git repositories. Eg I had to patch coreutils because touch failed. This was fixed in a newer corutils release. This actually means you can't use binaries at all.
Nice: You can use an API to switch to the rescue system, You probably can scale easily by API. You get kind of root server. Thus running virtualized systems yourself should be possible. NixOs booted in kvm mode (Qemu/ vnc like interface). However when upstart was started it restarted. When booting from hd the normal way nothing happened and I didn't know how to debug it.