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Enabling PDF to CBR Conversion in Stirling PDF

Overview​

Stirling PDF can convert PDF files into the Comic Book RAR (.cbr) format. This process relies on an external command-line utility, rar, which is not included by default. To enable this feature, you must first install the rar utility on your system and then make it accessible to Stirling PDF.

What is a CBR file?​

A CBR (Comic Book RAR) file is an archive used for distributing digital comic books. It is essentially a collection of sequential image files (e.g., JPEG, PNG) compressed into a single file using RAR compression.

While CBR is a popular format, it requires the proprietary rar utility for creation. Its more common, open-standard alternative is CBZ (Comic Book ZIP), which is supported by Stirling PDF out of the box.

Step 1: Install the rar Command-Line Utility​

This is a mandatory prerequisite for both Docker and non-Docker setups. The rar executable must be installed on the host machine.

Linux​

The easiest method is to use your distribution's package manager.

Debian / Ubuntu: The rar package is available in the non-free repository.

sudo apt update
sudo apt install rar

Fedora / CentOS / RHEL: The rar package is available in the RPM Fusion "non-free" repository.

# First, enable the RPM Fusion non-free repository for your system.
# See https://rpmfusion.org/Configuration for instructions.

# Then, install rar
sudo dnf install rar  # For Fedora, RHEL 8+, CentOS Stream
# or
sudo yum install rar  # For CentOS 7

Manual Installation (Any Linux Distribution):

  1. Visit the official download page: rarlab.com/download.htm.
  2. Download the "RAR for Linux x64" command-line version.
  3. Extract the archive and install the binary: 
    # The version number (e.g., 712, as of writing this guide) will change.
    # Use the actual filename.
    tar -xzf rarlinux-x64-*.tar.gz

    # Move the binary to a standard location in your system's PATH
    sudo mv rar/rar /usr/local/bin/

    # Ensure it has execute permissions
    sudo chmod +x /usr/local/bin/rar

Windows​

  1. Download the "WinRAR and RAR command line tools" from rarlab.com/download.htm.
  2. Extract the downloaded archive.
  3. Copy the rar.exe file to a folder that is included in your system's PATH environment variable. A common and reliable location is C:\Windows\System32.
  4. If Stirling PDF is already running, restart it to ensure it recognizes the updated PATH.

macOS​

The recommended method is to use the Homebrew package manager.

brew install rar

Step 2: Configure Stirling PDF​

After installing rar on your host system, follow the appropriate instructions for your environment.

For Non-Docker Users​

If you installed Stirling PDF directly on your operating system (without Docker), no further configuration is needed. As long as the rar command is available in your system's PATH, Stirling PDF will automatically (after restart) detect and use it.

For Docker Users​

For the binary to be accessible inside the container, you have to mount the binary as a volume.

Update your docker-compose.yml to include the volume mount. The path on the host side must match where you installed rar.

services:
  stirling-pdf:
    image: docker.stirlingpdf.com/stirlingtools/stirling-pdf:latest
    ports:
      - '8080:8080'
    volumes:
      - ./StirlingPDF/trainingData:/usr/share/tessdata
      - ./StirlingPDF/extraConfigs:/configs
      - ./StirlingPDF/customFiles:/customFiles/
      - ./StirlingPDF/logs:/logs/
      - ./StirlingPDF/pipeline:/pipeline/
      # Add the following line to mount the rar binary
      - /usr/local/bin/rar:/usr/local/bin/rar:ro

Note for Windows Docker Users: The host path must use forward slashes. For example, if you placed rar.exe in C:\Program Files\RAR, your volume mount would look like this:

# Example for Windows host path
- "C:/Program Files/RAR/rar.exe:/usr/local/bin/rar:ro"

Step 3: Verification​

Confirm that Stirling PDF can access the rar command.

  • For Docker Users: Execute a command inside the running container.

    docker exec -it stirling-pdf rar

  • For Non-Docker Users: Check if the rar command is recognized in your terminal.

    # On Linux and macOS
    which rar

    # On Windows
    where rar

In both cases, a successful setup will display the RAR version and usage information. An error like "command not found" means there is a problem with the installation or PATH.

Important Considerations​

License Note​

RAR is shareware. While it is free to use for personal, non-commercial purposes, business or commercial use may require purchasing a license. Please review the official RAR license terms on the RARLAB website for complete details.

Alternative: Use the CBZ Format​

For broader compatibility and to avoid proprietary software, using the CBZ (Comic Book ZIP) format is highly recommended.

  • CBZ uses the open and universal ZIP standard.
  • The PDF to CBZ tool is enabled in Stirling PDF by default and requires no extra software.
  • CBZ is supported by virtually all modern comic book reader applications.