Recover corrupted RPM database

RPM database consists of a number Berkeley DB   files in  /var/lib/rpm, the exception  is  __db.* files, which like cache files are updated for every rpm operation and they can be safely deleted.

#tested in Centos 5.5 
$ ls /var/lib/rpm
Basenames     __db.001  __db.003  Filemd5s  Installtid  Packages      Provideversion  Requireversion  Sigmd5
Conflictname  __db.002  Dirnames  Group     Name         Providename   Pubkeys         Requirename  Sha1header      Triggername
$ file /var/lib/rpm/Packages
/var/lib/rpm/Packages: Berkeley DB (Hash, version 8, native byte-order)

If one of the DB files is partially corrupted and it is still readable by /usr/lib/rpm/rpmdb_dump, you can reload the DB file and rebuild db.
$cd /var/lib/rpm

$rm -f __db*      
$mv Packages Packages.orig
$/usr/lib/rpm/rpmdb_dump Packages.orig | /usr/lib/rpm/rpmdb_load Packages
$/usr/lib/rpm/rpmdb_verify Packages
#if you got this error: db_verify: PANIC: fatal region error detected; run recovery
#make sure /var/lib/rpm/__db.* are cleaned
#It is unlikely to rebuilddb if rpmdb_verify fails
$rpm -v –rebuilddb

If one of the DB files is completely corrupted and it is not readable by rpmdb_dump, you have to restore from backup,
$cd /var/lib/rpm

$cp Packages Packages.bak
#simulate a damaged RPM DB file
$ >Packages
$ cp Packages.bak  Packages
# Simply restoring  from backup file won’t work
#file verification is successful 
$ /usr/lib/rpm/rpmdb_verify Packages
#but any rpm operation fails
$rpm -qa 
error: rpmdbNextIterator: skipping h#     294 Header V3 DSA signature: BAD, key ID e8562897
#Even “rpm –rebuilddb” fails
$rm -f __db.*
$rpm –rebuilddb
error: rpmdbNextIterator: skipping h#     294 Header V3 DSA signature: BAD, key ID e8562897
#Notice the error about signature: BAD? The Pubkeys have to be cleaned as well.
$ mv Pubkeys Pubkeys.bak
#all good after removing Pubkeys file, a new Pubkeys is generated automatically on “rpm –rebuilddb”
$ rm -f __db.*
$ rpm –rebuilddb
$ rpm -qa | head -2
man-pages-2.39-15.el5_4
bash-3.2-24.el5