Contents

edit how to install software

there are multiple possibilities, as there is:

edit system environment installation

  • software which is installed in the core system:
  • Note: it is important to NOT install using nix-env this time because of the kernel modules!
  • just add this line to the /etc/nixos/configuration.nix 
 environment.systemPackages = with pkgs; [
   zsh wget
 ];
  • afterwards do: 
 nixos-rebuild switch

edit normal user installation

  • software which is installed per user: 
nix-env -i links2

edit how to remove installed software

also depending on where the software was installed:

WARNIG: when you call 'nix-collect-garbage' or 'nix-store --gc' you might get problems with software which is installed 'per user' as the garbage collector will check all roots and remove software which is not enlisted in that roots. but i guess that the 'per user' software is not included as a root.

edit system environment installation

remove the entry in environment.systemPackages = [ ]; 

nixos-rebuild switch
nix-env --delete-generations old
nix-collect-garbage

edit normal user installation 

nix-env -e links2
nix-env --delete-generations old
nix-collect-garbage

edit how to list installed software

edit software per user

that works for each 'shell' of a single user: 

 nix-env -q '*'

the other command i don't know what it's good for: 

 nix-env -q '*' --system

edit software in the environment.systemPackages

there is no command to list that at this time (8jun2011)

but there is this workaround (tnx to niksnut!): 

 nix-store -q --references /var/run/current-system/sw

edit how to update installed software

edit software per user 

 nix-env -u '*'

edit software in the environment.systemPackages 

 nixos-rebuild switch

edit how to roll back software 

 nix-env --rollback

Also see nix-env --list-generations.

edit nix-channels

Since a few weeks (05/17/12 time of adding this to the wiki) there is a NixOS channel, which is now the default mechanism for keeping NixOS up to date. (A channel is a Nix mechanism for distributing a consistent set of Nix expressions and binaries.)

A quick summary on how to use it: 

 $ nix-channel --add http://nixos.org/releases/nixos/channels/nixos-unstable
 $ nix-channel --update
 $ nixos-rebuild switch

The NixOS channel contains a copy of Nixpkgs (but only the binaries for i686-linux and x86_64-linux), so after "nix-channel --update" you can install packages via nix-env: 

 $ nix-env -i thunderbird

or, if you prefer the "-A" option: 

 $ nix-env -iA nixos.pkgs.thunderbird

The advantages of using a channel over the previous way (doing "svn up 

 /etc/nixos/*" a.k.a. nixos-checkout) are:
  • Correctness: The channel is only updated to a new revision of NixOS/Nixpkgs if it passes certain tests - specifically, if all jobs in the "nixos:tested" view succeed (http://hydra.nixos.org/view/nixos/tested). So you have a reasonable certainty that the new version will actually work. By contrast, if you update to the latest revision using nixos-checkout, it's quite possible that somebody just committed something that broke the entire system.
  • Efficiency: The channel is only updated after all Hydra builds in that revision have finished, *and* all binaries have been mirrored. (Binary patches are generated asynchronously, however, since they can take much longer to produce.) So you don't have to worry about somebody just having committed something that causes a huge recompilation.

This makes keeping NixOS up to date a rather more pleasant activity, IMHO (Eelco Dolstra).

Some things to note:

  • The downloaded channel sources are stored in /nix/var/nix/profiles/per-user/root/channels/nixos (which is actually in the Nix store). The $NIX_PATH environment variable contains this directory, so <nixos> and <nixpkgs> in Nix expressions resolve there unless overriden through 
 $NIX_PATH or the "-I" flag.
  • In principle, you can do rollbacks on the channels profile ("nix-env -p /nix/var/nix/profiles/per-user/root/channels --rollback") if you don't like the result of a "nix-channel --update". However, this doesn't roll back the corresponding binaries manifest in /nix/var/nix/manifest so its utility is limited [1].
  • The NixOS installation CD no longer contains or installs /etc/nixos/{nixos,nixpkgs} but instead uses the NixOS channel. You can of course run "nixos-checkout" if you want a working tree for development. (In other news, "nixos-checkout" now accepts a argument to specify the desired location of the working trees, e.g. "nixos-checkout /home/eelco/Dev". The

default location /etc/nixos may eventually go away since it's a weird location for keeping large source trees.)

  • To use a development tree in nixos-rebuild, just use the -I flag, e.g. "nixos-rebuild switch -I /home/eelco/Dev".
  • The "nixpkgs_sys" link in ~/.nix-defexpr is no longer created. Instead you can use "nixos.pkgs" in "nix-env -iA" calls, as shown above. "nixos.pkgs" is the Nixpkgs in the NixOS channel, so it's guaranteed to have binaries available.
  • The command "nixos-version" prints out the NixOS version you're currently running, e.g. "0.1pre34067-34075". The version string include the NixOS and Nixpkgs revisions, respectively. If you install from SVN it just prints "0.1pre-svn".
  • Old versions can be installed from http://nixos.org/releases/nixos/. These are periodically deleted because they take up a lot of space. (Note that the nixos-unstable channel is really just a link to the latest NixOS release.)

[1] In the future we may get rid of manifests, in which case the Right Thing would happen magically.

edit nix-channels vs nixos-checkout

using nix-channels and nixos-checkout in parallel can lead to duplicated entries using nix-* tools.

edit how to change the used kernel version

boot.kernelPackages # see http://hydra.nixos.org/build/1106908/download/1/nixos/manual.html

for example: add 

 boot.kernelPackages = pkgs.linuxPackages_2_6_25;

to your /etc/nixos/configuration.nix

or check for more recent entries by: 

 nix-env -qa '*' | grep linux-2.6.
Retrieved from "http://nixos.org/wiki/Install/remove_software"