Eu encontrei esta solução:
#!/bin/bash
# get-package-list-from-backup.sh
set -e
set -x
cd /var/adm/backup/rpmdb
for gzipfile in *.gz; do (
base=${gzipfile/.gz/}
dir=/var/tmp/rpmdb-restore-$base
mkdir $dir
cp $gzipfile $dir
cd $dir
gunzip $gzipfile; mv $base Packages
rpm --dbpath $dir -qa | sort > qa.list )
done
Agora posso ver as diferenças:
vimdiff /var/tmp/rpmdb-restore-Packages-20150625/qa.list /var/tmp/rpmdb-restore-Packages-20160311/qa.list