5.1 Preconditions
An install begins with a package file already fetched, the repository it came from with its trust state, the current database state, and the plan that called for the install.
The following hold before the install proceeds:
- The package's hash matches what the repository index recorded.
- The package's signature, if present, verifies against the trust set scoped to its originating repository.
- The package is not already installed at the same version and architecture in this root.
- The package's architecture is the system's primary architecture or
noarch. - The package's dependencies are satisfied by the installed set, by the plan in flight, or by both together.
- No installed package conflicts with it.
A precondition failure aborts the install, and the transaction containing it is rolled back.
5.1.1 Verification before extraction #
For a transaction containing several installs or upgrades, every package's signature and index-hash verification completes before any package's payload is extracted.
Within a single root, the guarantee holds: every package is provided and verified before the first is materialised.
Across roots it does not. A cross-root transaction prepares and applies each root in sequence, so one root's payload is on disk in its final location before the next root's packages have been fetched or verified.