How to Run Unrar in Background Mode at Low Priority

This article explains how to configure the unrar command-line utility to extract archives silently in the background while minimizing system resource consumption. You will learn the exact command switches required to lower process priority, throttle execution speed, and decouple the task from your active terminal or desktop environment.

The Priority Switch: -ri

The switch that controls execution priority and regulates system load in unrar is -ri<p>[:<s>].

  • p (Priority): Sets task priority on a scale from 0 to 15. Setting this value to 1 instructs unrar to run at the lowest possible process priority, allowing other applications full access to the CPU. Setting it to 0 uses the system default.
  • s (Sleep time): An optional parameter measured in milliseconds (from 0 to 255) that forces unrar to pause between read or write cycles, further lowering disk and CPU utilization.

To extract an archive at the lowest system priority with a 10-millisecond sleep delay, use:

unrar x -ri1:10 archive.rar

The Background Switch: -ibck

In Windows console environments, unrar includes the dedicated -ibck switch to send the operation directly to the background. When specified, this switch suppresses the main console window and places an icon into the system notification tray instead.

To run unrar simultaneously in the background and at the lowest priority:

unrar x -ibck -ri1 archive.rar

Running in the Background on Linux and Unix

On Linux and macOS systems where -ibck may not be supported by the native command-line build, background execution with low priority is handled natively by the shell using nice alongside standard background job control:

  • Lower Priority (nice): Run nice -n 19 unrar x archive.rar to assign the lowest scheduling priority (niceness value 19).
  • Background Execution (& / nohup): Append an ampersand (&) or prefix the command with nohup to detach the task from your shell session:
nohup nice -n 19 unrar x archive.rar > /dev/null 2>&1 &

This ensures the extraction process operates entirely unattended in the background without degrading system responsiveness.