Usuage: Add breakpointHook to your `buildInputs` like this:
stdenv.mkDerivation rec {
# ...
buildInputs = [ breakpointHook ];
});
When the build fails as show in this example:
pkgs.hello.overrideAttrs (old: {
buildInputs = [ breakpointHook ];
postPatch = ''
false
'';
});
It will halt execution printing the following message:
build failed in patchPhase with exit code 1
To attach to this build run the following command as root:
cntr attach -t command cntr-/nix/store/ynyb4n82x2r7sldd58pbb405jdqh5f00-hello-2.10
Installing cntr and running the command will provide shell access to the
build sandbox of failed build:
sudo cntr attach -t command cntr-/nix/store/ynyb4n82x2r7sldd58pbb405jdqh5f00-hello-2.10
WARNING: bad ownership on /nix/var/nix/profiles/per-user/root, should be 1000
[nixbld@localhost:/var/lib/cntr]$
At /var/lib/cntr the sandbox filesystem is mounted. All commands and
files of the system are still accessible within the shell.
To execute commands from the sandbox use the `cntr exec` subcommand.
