pyrox.dev
1# pkgs.checkpointBuildTools {#sec-checkpoint-build}
2
3`pkgs.checkpointBuildTools` provides a way to build derivations incrementally. It consists of two functions to make checkpoint builds using Nix possible.
4
5For hermeticity, Nix derivations do not allow any state to be carried over between builds, making a transparent incremental build within a derivation impossible.
6
7However, we can tell Nix explicitly what the previous build state was, by representing that previous state as a derivation output. This allows the passed build state to be used for an incremental build.
8
9To change a normal derivation to a checkpoint based build, these steps must be taken:
10 ```nix
11 {
12 checkpointArtifacts = (pkgs.checkpointBuildTools.prepareCheckpointBuild pkgs.virtualbox);
13 }
14 ```
15 ```nix
16 {
17 changedVBox = pkgs.virtualbox.overrideAttrs (old: {
18 src = path/to/vbox/sources;
19 });
20 }
21 ```
22 - use `mkCheckpointBuild changedVBox checkpointArtifacts`
23 - enjoy shorter build times
24
25## Example {#sec-checkpoint-build-example}
26```nix
27{
28 pkgs ? import <nixpkgs> { },
29}:
30let
31 inherit (pkgs.checkpointBuildTools) prepareCheckpointBuild mkCheckpointBuild;
32 helloCheckpoint = prepareCheckpointBuild pkgs.hello;
33 changedHello = pkgs.hello.overrideAttrs (_: {
34 doCheck = false;
35 postPatch = ''
36 sed -i 's/Hello, world!/Hello, Nix!/g' src/hello.c
37 '';
38 });
39in
40mkCheckpointBuild changedHello helloCheckpoint
41```