10.3 Cross-Root Dependencies
A dependency is satisfied within a root. By default that is the
depending package's root, so a package's closure flows into the root the
package occupies. A dependency's root field names a different one.
declares that the dependency is required in the initramfs root, wherever the depending package lives.
10.3.1 Routing #
Every placement decision passes through one point: given a dependency
and the depending package's root, choose the target root. An empty
root field, or single-root mode, keeps the dependency where the
depender is; otherwise the name is looked up in the live registry.
A root naming something not registered is a resolution failure —
unsatisfiable, naming the root — rather than a silent fallback.
Cross-root edges are honoured in plan ordering and in the reverse-dependency check that decides what a removal breaks.
10.3.2 Which verbs route #
install resolves cross-root. upgrade, downgrade, uninstall, and
undo resolve single-root, where a dependency's root field is inert
and the dependency is evaluated in the depending package's root instead.
So a cross-root dependency is placed correctly when the depending package is installed, and is evaluated in the wrong root on every later operation.
10.3.3 Satisfier identity #
A satisfier is identified by the pair (name, root). The same package name installed in two roots is two independent installations, possibly at different versions, and a dependency is satisfied only by an installation in the root it names.
10.3.4 Top-level placement #
Where an operator names a package directly with no explicit --root,
the package's default_root decides where it lands. peipkg applies it
once, before building the resolver's requests, and only when the
operator did not pass --root — a defaulted root does not count as
explicit.
If the named packages declare no default, the current root is used. If
they declare exactly one distinct default, the whole install is
re-rooted there. If they declare two or more different defaults, peipkg
stops and tells the operator to split the command or pass --root,
rather than picking one.
A dependency's placement is never governed by its own default_root;
only by the depending package's root and the dependency's root field.
10.3.5 Cross-root garbage collection #
Removing the last thing in a root that required a cross-root dependency does not remove that dependency from the other root. Cross-root autoremoval is not implemented; the dependency stays until something removes it explicitly.