2. Creating and configuring a session

#include <libdnf5/base/base.hpp>

// Create a new Base object.
libdnf5::Base base;

// Optionally set installroot.
//
// Installroot is set to '/' when we're working with the system, but we can set
// it to a different location. The Base instance will then work with the
// installroot directory tree as its root for the rest of its lifetime.
base.get_config().get_installroot_option().set(installroot);

// Optionally - Prevent loading libdnf5 plugins.
// Plugins are loaded by default from the host
base.get_config().get_plugins_option().set(false);

// Optionally load configuration from the config files.
//
// The Base's config is initialized with default values, one of which is
// "config_file_path". This contains the default path to the config file
// ("/etc/dnf/dnf.conf"). If the file does not exist the distribution config file
// is loaded. Function also loads configuration files from distribution and
// user ("/etc/dnf/libdnf5.conf.d") drop-in directories.
// Optionally set a custom value to "config_file_path" before calling this method
// to load configuration from a another configuration file.
base.load_config();

// Load vars and do other initialization (of libsolv pool, etc.) based on the
// configuration.  Locks the installroot and varsdir configuration values so
// that they can't be changed.
base.setup();

2.1. Override the system architecture

For the dnf5 command-line tool, the –forcearch, dnf5-forcearch(7) option is available. Here’s how you can achieve the same effect using the API:

#include <libdnf5/base/base.hpp>

// Create a new Base object.
libdnf5::Base base;

// Optionally load configuration from the config files.
base.load_config();

// Override the detected system architecture, similar to how the
// `--forcearch=aarch64` switch works in the dnf5 command line tool.
base.get_vars()->set("arch", "aarch64");

// This is sufficient for loading repositories and querying packages using the
// `aarch64` architecture.
// However, if you also want to run a transaction (e.g., you want to modify a
// foreign system from "outside" using `installroot`), you need to set the
// `ignorearch` option to instruct RPM to permit packages that are incompatible
// with the system architecture.
base.get_config().get_ignorearch_option().set(true);

// The base.setup() call configures the architecture for the solver, so the
// `arch` variable needs to be set beforehand.
base.setup();