nix-env-rebuild

Declaratively manage a nix user environment.

nix-env-rebuild works similarly to how nixos-rebuild works for system packages: it reads a set of declared packages from configuration files and modifies the user profile such that it contains exactly those declared packages.

Features:

• Upfront configuration of the user environment through config files
• Commands in the spirit of nixos-rebuild: dry-run, build, and switch
• The command dry-run shows a detailed summary of how the current environment would change
• Support for overriding nixpkgs with store-paths

Installation

Because Nix is so awesome, you can simply clone the repo and run

▶ nix-build -E 'with (import <nixpkgs> {}); with haskellPackages; callPackage ./. { }'

Usage

The set of declared packages is determined by a Nix-expression read from the packages file (option --packages, default ~/.nixpkgs/packages.nix) and, optionally, by a list of store-paths (option --store-path-list, default ~/.nixpkgs/store-paths.txt). Store paths override entries in the packages file.

Packages file example:

# file ~/.nixpkgs/packages.nix
with import <nixpkgs> {};
[ emacs
  firefox
  owncloudclient
  cabal-install
]

Store path list example

# file ~/.nixpkgs/store-paths.txt
#  Specify one store path per line.
#  Start comments with a hash ('#').
#  Blank lines are ignored.
/nix/store/k1i2i013n3p1y3bb6b48ljzz7iz29ajf-TeXLive-linkdir
/nix/store/fb0x101j8aprznhnjhyj2vvny81k6b15-git-2.6.3
/nix/store/wd4d4i3l2ywij3q8pzhzn4kxmxx29av3-cabal-install-1.22.7.0

Given the above files, running

nix-env-rebuild switch 

results in a user profile containing

• the packages emacs, firefox, and owncloudclient according to nixpkgs, and
• the packages TeXLive-linkdir, git, and cabal-install according to the given store-paths
• and nothing else

(note that in this example, the store-path /nix/store/wd4d4i3l2ywij3q8pzhzn4kxmxx29av3-cabal-install-1.22.7.0 overrides the cabal-install entry in packages.nix)

Commands

There are three commands:

• dry-run: Calculate and display a summary on how the selected profile would change when doing a rebuild. Does not actually install anything. See "Update output" below for an explanation of the summary.
• build: Install the declared packages into a cache profile (option --cache-profile, default $NIX_USER_PROFILE_DIR/nix-env-rebuild-cache). Does not modify the selected profile.
• switch: Install the declared packages into the selected profile.

Update summary explained

Suppose we have a current profile with these packages installed.

▶ nix-env -q 
cabal-install-1.22.7.0
evince-3.18.2
firefox-42.0
git-2.7.0
owncloud-client-1.7.1

Using packages.nix and store-paths.txt from above, nix-env-rebuild dry-run will report the following:

* Calculating updates
  - packages from [...]
  - store-paths from [...]
  - search path [...]


Updating:
  firefox (42.0 -> 44.0 Prebuilt)
  git (2.7.0 -> 2.6.3 Present)
 
Adding:
  TeXLive-linkdir
  emacs-24.5
 
Reinstalling from source:
  owncloud-client-1.7.1
 
Removing:
  evince-3.18.2
 
Updates through store-path packages:
  git (2.7.0 -> 2.6.3 Present)
 
Updates and reinstalls blocked by store-path packages:
  cabal-install (1.22.7.0 -> 1.22.8.0 Prebuilt)

Dry run. Not doing anything.

The summary has these categories:

• Updating: Packages that are updated because there is a newer version available in nixpkgs (here firefox and git).
• Adding: Packages that are not present in the current profile, but listed in packages.nix (emacs, TeXLive-linkdir).
• Removing: Packages that are currently installed but are not listed packages.nix or store-paths.txt (evince).
• Updates through store-path packages: the subset of updates that is triggered by store-paths.txt.
• Updates and reinstalls blocked by store-path packages: packages that would be updated according to nixpkgs but are kept at the currently installed version by an override in store-paths.txt.