AppImageUpdate

A Rust implementation of AppImageUpdate - a tool for updating AppImages using efficient delta updates.

Features

• Delta Updates - Only download the changed portions of the AppImage, saving bandwidth and time
• Decentralized - No central repository required; updates come directly from the source
• Multiple AppImages - Update or check multiple AppImages at once
• Directory Scanning - Pass a directory to update all AppImages inside
• Smart Grouping - AppImages with the same update source share downloads
• Progress Display - Real-time progress during updates
• Checksum Verification - SHA1 verification ensures downloaded files are valid
• Permission Preservation - Maintains executable permissions from the original AppImage
• Skip Unnecessary Updates - Automatically skips update if the target file already exists with the correct checksum
• In-Place Updates - Updates to same filename preserve old version as .old backup

Installation

From Source

git clone https://github.com/pkgforge-dev/appimageupdate.git
cd appimageupdate
cargo install --path .

Usage

Update an AppImage

appimageupdate ./myapp.AppImage

Output:

Source:   ./myapp.AppImage (85.3 MB)
Target:   ./myapp-2.0.AppImage (92.1 MB)

Performing delta update...
Progress: 100% (92.1/92.1 MB)

Reused:        42.1 MB  (1247 blocks)
Downloaded:    50.0 MB  (1482 blocks)
Saved:         42.1 MB  (45%)

Updated: ./myapp-2.0.AppImage

Update Multiple AppImages

appimageupdate ./app1.AppImage ./app2.AppImage ./app3.AppImage

Update All AppImages in a Directory

appimageupdate ~/Applications/

Check for Updates

Check a single AppImage:

appimageupdate -j ./myapp.AppImage

Check multiple AppImages:

appimageupdate -j ~/Applications/

Output:

Checking: /home/user/Applications/app1.AppImage ... Update available
Checking: /home/user/Applications/app2.AppImage ... Up to date
Checking: /home/user/Applications/app3.AppImage ... Update available

Exit code 1 if any update available, 0 if all up to date.

Describe an AppImage

appimageupdate -d ./myapp.AppImage

Output:

Path:         ./myapp.AppImage
Size:         85.3 MB
Target:       ./myapp-2.0.AppImage
Target Size:  92.1 MB
Update Info:  gh-releases-zsync|user|repo|latest|*.AppImage

Options

appimageupdate [OPTIONS] [APPIMAGE]...

Arguments:
  [APPIMAGE]...           Path(s) to AppImage(s) or directories to update

Options:
  -O, --overwrite         Overwrite existing target file
  -r, --remove-old        Remove old AppImage after successful update
  -u, --update-info <INFO> Override update information in the AppImage
      --output-dir <DIR>  Output directory for updated AppImages
  -d, --describe          Parse and describe AppImage and its update information
  -j, --check-for-update  Check for update (exit 1 if any available, 0 if not)
      --github-api-proxy <URL>  GitHub API proxy URL [env: GITHUB_API_PROXY]
                           (supports comma-separated list for fallback)
  -h, --help              Print help
  -V, --version           Print version

How It Works

1. Reads Update Information - Extracts embedded update info from the AppImage's .upd-info ELF section
2. Fetches Zsync Metadata - Downloads the .zsync control file which contains block checksums and file metadata
3. Calculates Delta - Compares local file blocks against remote blocks using rolling checksums
4. Downloads Only Changes - Fetches only the blocks that differ from the local copy
5. Assembles & Verifies - Reconstructs the file and verifies SHA1 checksum

Configuration

Create a config file at ~/.config/appimageupdate/config.toml:

# GitHub API proxy (supports single or multiple for fallback)
github_api_proxy = "https://ghproxy.net"
# Or multiple proxies:
# github_api_proxy = ["https://ghproxy.net", "https://mirror.example.com"]

# Remove old AppImage after successful update
remove_old = true

# Output directory for updated AppImages (supports shell expansion)
output_dir = "~/Applications"

Environment Variables

Variable	Description
GITHUB_API_PROXY	GitHub API proxy URL (comma-separated for multiple)
APPIMAGEUPDATE_REMOVE_OLD	Set to true to remove old AppImage after update
APPIMAGEUPDATE_OUTPUT_DIR	Output directory for updated AppImages

Priority: CLI args > Environment variables > Config file

Supported Update Formats

• zsync|<url> - Direct zsync URL
• gh-releases-zsync|<user>|<repo>|<tag>|<filename> - GitHub releases with glob pattern matching

Comparison with Upstream

This is a Rust rewrite of the upstream AppImageUpdate (C++/Qt).

Advantages:

• Single static binary with no runtime dependencies
• Over 10x smaller
• Cleaner, more maintainable codebase
• URL caching to avoid redundant API calls
• Proxy support
• Better error messages

Differences:

• No GPG signature verification (not implemented)
• No pling integration (not implemented)
• No GUI (not implemented)

Library Usage

use appimageupdate::{Updater, Error};

fn main() -> Result<(), Error> {
    let updater = Updater::new("./myapp.AppImage")?;

    if updater.check_for_update()? {
        let (path, stats) = updater.perform_update()?;
        println!("Updated to: {}", path.display());
        println!("Saved {}% bandwidth", stats.saved_percentage());
    } else {
        println!("Already up to date!");
    }

    Ok(())
}