# NixOS configuration broke, brightness keys don't work, no idea what I changed
**URL:** https://discourse.nixos.org/t/nixos-configuration-broke-brightness-keys-dont-work-no-idea-what-i-changed/5533
**Category:** Help
**Created:** [January 17, 2020, 11:31pm UTC](https://discourse.nixos.org/t/nixos-configuration-broke-brightness-keys-dont-work-no-idea-what-i-changed/5533 "2020-01-17T23:31:59Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@trusktr](https://discourse.nixos.org/u/trusktr)
#### Post date: [January 17, 2020, 11:31pm UTC](https://discourse.nixos.org/t/nixos-configuration-broke-brightness-keys-dont-work-no-idea-what-i-changed/5533/1 "2020-01-17T23:31:59Z")
The reason I’m asking about [See diff between generation configurations. Or see previous generation's configuration.nix](https://discourse.nixos.org/t/see-diff-between-generation-configurations-or-see-previous-generations-configuration-nix/5493) is because my brightness keys stopped working, and it is now difficult to figure out what exactly I changed to break it.
TLDR: there’s no way to see what my previous configuration was, and I unfortunately did not version control my `configuration.nix`.
The only thing I can try to do is rollback, but that’s not helpful because I won’t know what the actual problem is. Overall it is difficult to actually know what a problem is, as rolling back doesn’t really help you with that.
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### Author:  [@layus](https://discourse.nixos.org/u/layus)
#### Post date: [January 18, 2020, 7:51am UTC](https://discourse.nixos.org/t/nixos-configuration-broke-brightness-keys-dont-work-no-idea-what-i-changed/5533/2 "2020-01-18T07:51:57Z")
Not sure what your question is here, but it may not be the configuration.nix changes that did anything. Did you update your channel in the meantime ? Did you reboot in the meantime ? To know for sure, you could rollback and see if the problem disappears. If not, it is not linked to that system change.
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### Author:  [@trusktr](https://discourse.nixos.org/u/trusktr)
#### Post date: [January 18, 2020, 8:36am UTC](https://discourse.nixos.org/t/nixos-configuration-broke-brightness-keys-dont-work-no-idea-what-i-changed/5533/3 "2020-01-18T08:36:45Z")
> [@layus](#):
>
> Did you update your channel in the meantime
As far as I know, I didn’t. I haven’t explicitly ran with the `--update` flag. I did also reboot a few times. I decided to move forward and try tweaking configuration.nix, so I added several packages, and the problem seems to have fixed itself after some changes, though I don’t recall changing anything major except setting `xkbOptions` and adding some packages.