Config aria2 to drop download if resume unsupported?

This article provides a direct solution for configuring the aria2 command-line download utility to automatically abort a download if the remote server does not support resuming. By default, aria2 will restart a download from scratch if a connection drops and the server lacks resume capabilities, which can waste significant time and bandwidth. Below, you will find the specific configuration flags required to change this behavior, along with examples for both the command line and configuration files.

The aria2c Configuration Flags

To force aria2 to drop a download when resume is unsupported, you need to combine two specific command-line options: --conditional-get and --allow-overwrite.

• --conditional-get=true: This tells aria2 to check if the remote file has been modified or if the server supports the features required to resume. If the server does not support the necessary headers (like ETag or Last-Modified) to validate and resume the transfer safely, aria2 will handle the download based on your overwrite settings.
• --allow-overwrite=false: When set to false, this prevents aria2 from simply deleting your existing partial download and starting over from 0% when a resume fails. Instead, it will throw an error and terminate the process.

Command Line Implementation

When starting a download from the terminal, you can append these flags directly to your command:

aria2c --conditional-get=true --allow-overwrite=false "https://example.com/largefile.zip"

If the server at example.com does not support resuming, aria2 will stop immediately instead of wiping your progress and restarting the download from the beginning.

Persistent Configuration File Setup

If you prefer not to type these flags every time, you can add them to your global aria2 configuration file (typically located at ~/.config/aria2/aria2.conf on Linux/macOS or in the same directory as the executable on Windows).

Open your aria2.conf file and add the following lines:

# Abort download if resume is not supported by the server
conditional-get=true
allow-overwrite=false

Once saved, aria2 will apply this logic to all future download tasks automatically, safeguarding your bandwidth against unresumable connections.