Yum broke Perl on CentOS 5

During a recent Yum update that was long overdue, my perl scripts stopped working talking about missing XS versions of certain perl modules.

Specifically it broke my script that uses Mail::Box::Manager and complained about a dependency fail in Mail::Box::Reporter that needed an XS version that is missing.

I thought I would re-install Mail::Box::Manager. While trying to manually compile Mail::Box::Manager (since CPAN won't install without force, which is a bad idea if something is really broken), one of the first warnings given is

--
!!!! WARNING !!!! On your system, the module Scalar::Util is installed
!!!! WARNING !!!! without use of XS. This means that critical functionality
!!!! WARNING !!!! is missing. Reinstall the module and be sure to get the
!!!! WARNING !!!! correct installation.
!!!! WARNING !!!! perl -MCPAN -e 'shell'
!!!! WARNING !!!! > force install Scalar::Util
--

This led to the bug below that recommends force installing Scalar::Util via CPAN, since CentOS RPMs don't have this and is missing the XS version.
http://bugs.centos.org/view.php?id=2434

Force installing Scalar::Util as indicated worked. Phew! Took me 2 days to research this, but finding a simple solution to fix everything is great. :)

perl xml parser and dependency hell

Was trying to install a perl module from CPAN (Frontier::Daemon) which needed XML::Parser which just wouldn't install. Perl's package manager kept complaining about a missing expat.h file, followed by many lines of errors. yum said expat is up to date. Removing expat (in an effort to reinstall it) removed yum as well. Installing yum wasn't easy. Finally got the rpm for yum to work and installed CentOS's precompiled perl xml parser. perl was satisfied with this and installed Frontier::Daemon without further complaints.

When Yum Corrupts Its Own rpm Database

I was using yum the other to update a CentOS 5 server after a long time. It got stuck on a long download and didn't seem to quit even after a long time. Tried ending the process using

> kill pid
> kill -INT pid

This did nothing and the process was still hung. Finally used the trusty but dangerous kill -9 which terminated the process. But this made matters worse. Now yum wouldn't even start. A quick google search led to someone speculating that such forceful killing of the process could have corrupted the rpm database. Per their suggestion,

> rm /var/lib/rpm/__db*
> rpm --rebuilddb
> yum clean all

This fixed everything. Not sure what the above does exactly, but hopefully it's ok. This was not a production box, so it was fine. Yum works!