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lxc/ — what runs inside the container

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Once the host has created a container, it runs one of these inside it. The host passes the file through the environment (FUNCTIONS_FILE_PATH), which lxc-attach carries into the container.

install.func

The multi-distro bootstrap: Debian, Ubuntu, Devuan, Fedora, Rocky, Alma, CentOS, openSUSE, Gentoo, openEuler.

A container has its own filesystem, so the host's prefetch cannot help it. _cs_ct_prefetch_engine therefore fetches the container's own subset concurrently on this side, listed in _CS_CT_ENGINE_FILES, and _cs_engine_read reads from that copy or falls back to the network. Names are folder-qualified paths, the same as on the host.

Which helper library gets loaded is decided here: lib/alpine.func for Alpine, lib/tools.func otherwise.

Alpine used to get its own bootstrap, alpine-install.func. It was a second, thinner copy of the same eight functions, so every fix had to be made twice and install.func's own apk and OpenRC branches never ran. Both backends now hand install.func to every container and detect_os decides the rest.

platform.func

detect_lxc_platform and the predicates around it (is_incus_host, is_incus_container, is_incus_lxc_backend). This is what core/build.func uses to decide which backend to load: a Proxmox VE host, an Incus host, or already inside a container. It answers pve, incus, incus-container or container; loading.md covers the order the tests run in and why.

Two supporting pieces live here as well:

  • _lxc_incus_bin and ensure_incus_on_path — the incus client is not always on PATH, and detection finding it is not enough, because every later incus call in the engine has to resolve too.
  • community_scripts_dir — the writable state directory for defaults, diagnostics, logs and the header cache. /usr/local/community-scripts for root, or wherever that path is writable; ~/.config/community-scripts otherwise; COMMUNITY_SCRIPTS_STATE_DIR overrides both. It sits here rather than in core/ because the non-root case is an Incus one — a Proxmox VE host is always root, an Incus host frequently is not.