OPkg

OPKG is a lightweight package management system for embedded Linux. It provides facilities to install, upgrade, and remove software packages while resolving dependencies and managing repository feeds. OPKG uses the IPK package format, a small archive that typically carries control information and a data payload.

OPKG originated as a successor to the IPKG project and is widely used in embedded Linux distributions such as OpenWrt, OpenEmbedded, and Angstrom. It is designed for small footprint and simple operation on devices with limited resources.

OPKG operates by reading package metadata from configured feeds, storing a local package database, and downloading packages as needed. The typical files and directories include a status database at /var/lib/opkg/status, cache and lists under /var/cache/opkg and /var/lib/opkg/lists, and configuration in /etc/opkg.conf. Feeds are defined in one or more opkg configuration files, allowing multiple repositories to be queried.

Common commands include: opkg update to update package lists; opkg install <package> to install a package; opkg upgrade to upgrade installed packages; opkg remove <package> to remove; opkg list to enumerate available or installed packages; opkg search <pattern>; opkg files <package> to list files installed by a package. Packages themselves are typically named with the .ipk extension.

OPKG emphasizes simplicity and a low footprint, making it suitable for devices with constrained CPU, memory, and storage. It interacts with repositories that provide IPK packages and metadata, and can support basic integrity checks and signature verification depending on build and configuration.