multilib

Multilib is a feature of operating systems and software distributions that enables the installation and execution of software across multiple processor architectures on a single host, most commonly 32-bit and 64-bit x86 architectures. The primary use is to provide compatibility for older applications and development workloads that require 32-bit libraries while a 64-bit system is in place.

Implementation generally relies on architecture-specific library directories and a dynamic linker capable of selecting the correct library for a given process. On many Linux distributions, this entails separate library paths such as /lib and /usr/lib for 64-bit code and /lib32 and /usr/lib32 (or similar) for 32-bit code, or a multiarch framework that tags packages by architecture. Package managers install and track two sets of libraries, for example lib32-*-packages or libc6:i386 in a multi-arch system. Debian and derivatives use a multiarch approach, enabling commands like dpkg --add-architecture i386 and apt to install 32-bit libraries; Arch Linux maintains a dedicated multilib repository that provides 32-bit compatibility libraries for use on 64-bit systems.

Benefits include the ability to run legacy software and games, simplify development against multiple ABIs, and avoid full virtualization for compatibility tasks. Drawbacks involve increased system maintenance, larger disk usage, potential security concerns from having more packages, and the complexity of keeping both architectures' libraries in sync.

Multilib is commonly contrasted with containers or virtualization as isolation strategies; it is most widely discussed in Linux distributions, though other operating systems offer similar compatibility layers or multi-ABI support.