A shepherd for your Appimages.
dwarfs: don't fallback to executable bc dwarfsextract is a hard dep now
Aly Raffauf
(Jun 20, 2026, 1:00 AM EDT)
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README.md
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README.md
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## Under the hood
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AppHerder reads the AppImage's filesystem to grab its icon and desktop entry. SquashFS images are parsed in-process. DwarFS images use the system dwarfsextract tool, falling back to the AppImage's own runtime when the tool isn't available. Everything it writes is tagged, so uninstall and sync only touch its own files.
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AppHerder reads the AppImage's filesystem to grab its icon and desktop entry. SquashFS images are parsed in-process. DwarFS images require `dwarfsextract`; the AppHerder CLI AppImage bundles it, while native and source installs need `dwarfsextract` available on `PATH`. AppHerder does not automatically fall back to `--appimage-extract`, because that executes the AppImage runtime. Everything it writes is tagged, so uninstall and sync only touch its own files.
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## License
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internal/appherder/dwarfs.go
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internal/appherder/dwarfs.go
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"io/fs"
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"os"
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"os/exec"
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"path/filepath"
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"time"
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)
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// openDwarFS extracts the DwarFS payload from an AppImage. Tries the system
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// dwarfsextract tool first; falls back to the AppImage's own --appimage-extract
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// as a last resort. Returns the extracted filesystem and a cleanup function.
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// openDwarFS extracts the DwarFS payload from an AppImage using dwarfsextract.
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// It intentionally does not fall back to --appimage-extract, because that
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// executes the AppImage runtime.
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func openDwarFS(ctx context.Context, appimagePath string) (fs.FS, func(), error) {
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dir, err := os.MkdirTemp("", "appherder-dwarfs")
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if err != nil {
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ctx, cancel := context.WithTimeout(ctx, 5*time.Minute)
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defer cancel()
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cmd := extractCommand(ctx, appimagePath, dir)
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cmd, err := extractCommand(ctx, appimagePath, dir)
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if err != nil {
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cleanup()
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return nil, nil, err
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}
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if out, err := cmd.CombinedOutput(); err != nil {
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cleanup()
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return nil, nil, fmt.Errorf("extract DwarFS AppImage: %w\n%s", err, out)
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}
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// dwarfsextract -o extracts directly; --appimage-extract nests under squashfs-root.
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root := dir
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if _, err := os.Stat(filepath.Join(dir, "squashfs-root")); err == nil {
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root = filepath.Join(dir, "squashfs-root")
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}
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return os.DirFS(root), cleanup, nil
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return os.DirFS(dir), cleanup, nil
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}
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func extractCommand(ctx context.Context, appimagePath, destDir string) *exec.Cmd {
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func extractCommand(ctx context.Context, appimagePath, destDir string) (*exec.Cmd, error) {
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extract, err := exec.LookPath("dwarfsextract")
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if err == nil {
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return exec.CommandContext(ctx, extract,
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"--input="+appimagePath,
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"--output="+destDir,
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"--pattern=**.desktop",
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"--pattern=**.png",
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"--pattern=**.svg",
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"--pattern=.DirIcon",
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)
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if err != nil {
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return nil, fmt.Errorf("find dwarfsextract: %w", err)
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}
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// Fall back to the AppImage's own --appimage-extract. The file must be
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// executable for this to work.
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os.Chmod(appimagePath, 0o755)
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cmd := exec.CommandContext(ctx, appimagePath, "--appimage-extract")
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cmd.Dir = destDir
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return cmd
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return exec.CommandContext(ctx, extract,
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"--input="+appimagePath,
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"--output="+destDir,
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"--pattern=**.desktop",
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"--pattern=**.png",
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"--pattern=**.svg",
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"--pattern=.DirIcon",
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), nil
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}
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// isDwarFS reports whether the payload at offset starts with the DwarFS magic.