how-to fix the XS version of Scalar::Util error in CentOS / RHEL / Fedora

It’s being some month now that at work we have encountered a nasty problem with Perl’s module Compress::Zib usage in a tool developed by a colleague. At the moment to start the graphical rendering of a web page the system gave error to our users.

Searching in Apache2’s log I’ve encoutered many error of this kind:

dualvar is only available with the XS version of Scalar::Util at /var/www/html/$MY-APP-PATH/perl/Compress/ line 8

This is because the Scalar-List-Utils module precompiled in RHEL/Fedora/CentOS and similar does NOT have the support of XS weaken function.

You will see a lot of bugs issued on this topic in this part of Linux distro’s.

My solution was to install perl-Task-Weaken package:

In fact as we can read in the package’s description:

rpm -qi perl-Task-Weaken
URL         :
Summary     : Ensure that a platform has weaken support
Description : One recurring problem in modules that use Scalar::Util's weaken function is that it is not present in the pure-perl variant.

This restores the functionality testing to a dependency you do once in your Makefile.PL, rather than something you have to write extra tests for each time you write a module.

Happy coding!


What files are provided by $package.rpm?

Today I needed to install the openMPI package on a development machine, and occurred to me to know if by installing it the system’s GCC (and similar). So asked my friend Gianluca an hand and he pointed me to the repoquery command.

So I did the following:

yum whatprovides "*/repoquery"

which gived to me:

yum-utils-1.1.16-14.el5.centos.1.noarch : Utilities based around the yum package manager
Repo : base
Matched from:
Filename : /usr/bin/repoquery

so I did a simple:

yum install yum-utils

followed by a:

repoquery -ql openmpi-devel.x86_64

… and I obtained the needed infos. Thanks Gianluca!

migration from RHEL to CentOS, done!

Last year at work we brought a little server … you know, fiberchannel hard disks, 32GB of RAM, four quad core XEON … usual stuff 😉
We also got a 1 year of Red Hat Enterprise Linux subscription. Obviuosly this year the money for a renewal of it’s licence aren’t available so, to keep safe and up-2-date, what do we do?

features rhel

We’ve decided to migrate to CentOS, given their famous binary compatibility with the Prominent North American Enterprise Linux Vendor 😉 Thanks to the Lord the process was simple and straightfoward as shown on the page of the official CentOS’ wiki.

Even with the subscription to RHN out-of-date, I did manage to upgrade r5.4 to 5.5 … the process cleaned ALL the official RedHat’s repo files from /etc/yum.repos.d … so beware, make a backup copy of them.

Then I’ve disabled the (few) 3rd party repo sources from my system (they are currently just adobe, epel and remi).

At this point I’ve followed the advice to disable first, and remove later, the yum’s rhnplugin since some CentOS’s forum user issued some warning or error if that was not done. Hence the following commands sequence was given (as root):

cp /etc/redhat-release /etc/redhat-release-saved
rpm -e --nodeps redhat-release-notes redhat-release yum-rhn-plugin redhat-logos

We’ve nearly there … I’ve manually downloaded on the system the three packages: centos-release, centos-release-notes and redhat-logos-X.X.XX-XX.el5.centos.noarch.rpm from the nearest (and fastest) distribution mirror available (they are placed in the ../5/os/$YOUR-ARCH/CentOS/ directory, by the way) and then manually installed with plain old rpm.

yum update

completed the process and here we are:


[root@localhost ~]# cat /etc/issue
CentOS release 5.5 (Final)
[root@localhost ~]# uname -a
Linux localhost 2.6.18-194.3.1.el5 #1 SMP Sun May 2 04:17:42 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux


enable Java plugin on Firefox with CentOS or RHEL (64bit)

centos logo During last weeks I’ve installed and configuread a 64bit RHEL server, paying attention to include the open source java-openJDK and the official Sun’s JRE.

This morning a colleague called me via skype telling me that his Firefox didn’t have a proper Java plugin installed. At first glance I didn’t knew what to do and the first results of a Google’ session were useless refferring to old incompatibility between a 64bit Firefox and 32bit java vitual machine, old releases of both softwares, wrong *.so files to include.

Google and google I found this post, pointing the focus on the file which, on my machine, is placed under the /usr/java/jre1.6.0_16/lib/amd64/ path.

So I went to /usr/lib64/firefox-3.0.14/ folder {ignoring the old ones visible on the directory}, created a sub-directory called plugins (as root) and gave the command:

ln -s /usr/java/jre1.6.0_16/lib/amd64/

The I restarted Firefox and once loaded went to the Java Test Page to check my virtual machine installation and witnessed the correct, and aspected, result:

Your Java configuration is as follows:
Vendor: Sun Microsystems Inc.
Version: Java 6 Update 16
Operating System: Linux 2.6.18-164.2.1.el5
Architecture: amd64

Hope this will be useful to you too!

RedHat / CentOS release 5, interest gets higher

For the second time I have the impression of having been a little ahead of times when reporting some news.

This time I’m referring to my post “CentOS 5, first rumors” which is seeing a growing trend of access in these days:

CentOS post statistics

Well, the wait is near the end and today we the 13th March we had the announce:

This release corresponds to the upstream vendor EL5 beta2 release.

NOTE: This software is BETA and should be treated as such. It is for
testing purposes only. Please ensure it meets your needs completely
before using in a production environment.


Please see the CentOS specific release notes here:

which a bunch of hours ago was followed up by the official announcement of the release of Red Hat Enterprise Linux 5 I’ve been illustrating in the last week, so the CentOS 5 clone should be released very soon ….

Can’t wait to update my workstation (and possibly a server, we’ll see …)

Red Hat 5 graphics preview

RHEL gdm login page

( this time for real !!! )

Thanks to Francesco Ugolini, one of the (if not THE) most active Fedora Project’s ambassadors here in Italy, I’ve learned the existence of an apposite gallery page where the graphics of the newcoming Red Hat Enterprise Linux 5 overviewd by Diana Fong, one of the chief’s of Artwork team for both Fedora and Red Hat product lines.

If you watch carefully you will also see an hint of the much talked about Echo icon theme. Enjoy!

RedHat Enterprise Linux 5 landing?

Since some not better specified problems occurred, the original poster of the images I was referring on the original post have been removed.

For the love of infomation I can say that what was visible reminded some concepts seen on RedHat 5 beta2. Personally i did like what I saw !

Sorry for the inconvenient occurred pals 😦

UPDATE #2: to see some images go this post I made two days later!

Goodbye, ESR

redhat logo Have you heard about Eric S. Raymond leaving the Fedora project ?
If you – like me – are into “Linux” probably yes.
Well … what about the Alan Cox answer ?

On Wed, Feb 21, 2007 at 03:03:50AM -0500, Eric S. Raymond wrote:
* Failure to address the problem of proprietary multimedia formats with any attitude other than blank denial.

That would be because we believe in Free Software and doing the right thing (a practice you appear to have given up on). Maybe it is time the term “open source” also did the decent thing and died out with you.

Wow, what a temper !!!

RHEL-5 is coming

redhat logo With a couple of months of delay finally Red Hat, with an e-mail announcement into the mailing list dedicated to the issue, the 7th of september has announced to the world the release of the first “pubblic” beta of what will be ne new Red Hat Enterprise Linux 5.

In the month of September, in fact, was scheduled to appear the second beta release, but due to some claimed instability in the code of Xen – the system virtualization software that will be included in the release – there was this sliding of schedule.

I would like to remember that RHEL 5 is closely based on the work and efforts of the Fedora project, and specifically they are working side by side with the developement of the version 6 of Fedora Core (and not developing from FC 5, as someone could think). It’s logical to assume that we will se FC 6 “ship” before RHEL 5, which will come out very late this year.

The main points of innovation in this new release are:

  • * Network storage (Autofs, iSCSI)
  • * Kexec / Kdump (replacing Diskdump and Netdump)
  • * Smartcard integration
  • * SELinux Security
  • * Installer improvements
  • * Clustering and Cluster File systems
  • * Analysis and Development Tools (SystemTap, Frysk)
  • * Stateless Linux Enablers
  • * Infiniband and RDMA (OpenFabrics.Org)
  • * New Driver Model for better integration of out-of-kernel-tree drivers
  • Red Hat supports the following hardware architectures:

    – 32-bit x86-compatible (i386/i686)
    – 64-bit AMD64 and Intel EM64T (x86_64)
    – 64-bit Intel Itanium2 (ia64)
    – 64-bit IBM eServer iSeries and pSeries and POWER (ppc64)
    – 64-bit IBM eServer zSeries (s390x)

    In the end a couple of notes.

    I wrote public release because the beta three on the mirrors and the ISOs are available only to active Red Hat Network subscribers.

    Finally CentOS will come out with a beta of their 5th release soon after the RHEL team release the beta-2 of their product.

    Now i’m waiting to see some screenshot of it, maybe ultramookie will provide them, right pal ?


    UPDATE = an italian reader commented that @ the ISOs are freely downloadable.