On 01/20/2017 08:21 PM, John Walker wrote:
If anyone can give me any insight about how rpm rebuilds its database, or point me to
relevant portions of the source, I would appreciate it. ?
It reads the data records, ignoring any indexes, and creates a new
database from scratch. While reading the data records, it discards
those that fail basic sanity checks.
I'm new to rpm internals. When you say it reads the data records, which
data records do you mean? Records from the berkley database named
"Packages?" Records from several of the databases in the rpm database
directory? Something else entirely?
I feel like I'm misunderstanding something here, because if a rebuild
must be able to read records from the current database, it wouldn't do
much good if the current database is unreadable, however, I have found
that rpm --rebuilddb does work when the current database is unreadable,
at least in one limited situation. (db5-based version of rpm trying to
use files from a db4-based version of rpm.)
BDB is backwards compatible, a new version can always read data written
by older ones but not vice versa.
What is NOT compatible between different versions is the shared BDB
environment, ie the __db.* files you see in /var/lib/rpm. The trick with
--rebuilddb is that uses a private environment to avoid those
incompatibility, flagged PANIC'ed etc problems.
Other than that, it doesn't do anything special (no special mode to read
raw records), it just executes a 'rpm -qa' equivalent and generates a
new database with fresh indexes and all from all valid headers.
- Panu -
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