fix(generate): drop nix-store --optimise from generated dev Dockerfile

internal/devbox/generate/devcontainer_util_test.go

@@ -0,0 +1,56 @@
+// Copyright 2024 Jetify Inc. and contributors. All rights reserved.
+// Use of this source code is governed by the license in the LICENSE file.
+
+package generate
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// TestCreateDockerfileDevOmitsNixStoreOptimise ensures the generated dev
+// Dockerfile does not run `nix-store --optimise`. That command fails on Docker's
+// default overlay2 storage driver ("cannot rename: Stale file handle") and
+// breaks the image build, while providing negligible size savings in a freshly
+// built image. Regression test for
+// https://github.com/jetify-com/devbox/issues/2616.
+func TestCreateDockerfileDevOmitsNixStoreOptimise(t *testing.T) {
+	for _, rootUser := range []bool{false, true} {
+		dockerfile := generateDevDockerfile(t, rootUser)
+
+		if strings.Contains(dockerfile, "nix-store --optimise") {
+			t.Errorf("generated dev Dockerfile (rootUser=%t) should not run "+
+				"`nix-store --optimise`; it breaks Docker builds on overlay2.\n%s",
+				rootUser, dockerfile)
+		}
+		// The garbage-collection pass is still wanted: it removes build-time
+		// dependencies and is what actually shrinks the image.
+		if !strings.Contains(dockerfile, "nix-store --gc") {
+			t.Errorf("generated dev Dockerfile (rootUser=%t) should still run "+
+				"`nix-store --gc`.\n%s", rootUser, dockerfile)
+		}
+	}
+}
+
+func generateDevDockerfile(t *testing.T, rootUser bool) string {
+	t.Helper()
+
+	dir := t.TempDir()
+	g := &Options{
+		Path:     dir,
+		RootUser: rootUser,
+	}
+	if err := g.CreateDockerfile(t.Context(), CreateDockerfileOptions{
+		ForType: "dev",
+	}); err != nil {
+		t.Fatalf("CreateDockerfile failed: %v", err)
+	}
+
+	contents, err := os.ReadFile(filepath.Join(dir, "Dockerfile"))
+	if err != nil {
+		t.Fatalf("reading generated Dockerfile: %v", err)
+	}
+	return string(contents)
+}

internal/devbox/generate/tmpl/dev.Dockerfile.tmpl

@@ -21,7 +21,16 @@ COPY devbox.lock devbox.lock
 {{range $i, $element := .LocalFlakeDirs -}}
 COPY {{$element}} {{$element}}
 {{end}}
-RUN devbox run -- echo "Installed Packages." && nix-store --gc && nix-store --optimise
+{{- /*
+We run `nix-store --gc` to drop build-time dependencies and shrink the image,
+but intentionally do NOT run `nix-store --optimise`. Optimise hard-links
+duplicate files in the Nix store, and on Docker's default overlay2 storage
+driver the rename it performs fails with "cannot rename: Stale file handle",
+which breaks the image build. In a freshly built, single-purpose image there is
+little to no duplication to reclaim anyway, so the optimise pass provides
+negligible benefit. See https://github.com/jetify-com/devbox/issues/2616.
+*/ -}}
+RUN devbox run -- echo "Installed Packages." && nix-store --gc
 {{if .IsDevcontainer}}
 RUN devbox shellenv --init-hook >> ~/.profile
 {{- else}}