Tuesday, September 6, 2011

Fixing perl's CPAN on CentOS

If you are using CentOS 5.5 and trying to download perl modules with CPAN, you may come across this error:

Undefined subroutine &Compress::Zlib::gzopen called at /usr/lib/perl5/5.8.8/CPAN.pm line 5721

When working with Tivoli software, it is helpful to use virtual machines. You can save images for different app/version combinations and retrieve them when you need to develop or test something. CentOS is the open source brand for Red Hat, so it works really well when you have to install multiple VMs but don't want the hassle of tracking RHEL licenses. Sometimes you may have to modify various file contents to look more like RHEL itself, but in general CentOS does the trick.

Recently, I was attempting to write a perl script to parse XML files.  I chose to download the XML::LibXML module because it is very flexible and pretty fast. I started CPAN with:

user@system> cpan

Then I attempted the install:

user@system> install XML::LibXML

but then I got the 'Undefined subroutine...' error above. I tried running CPAN with the alternate command:

user@system> perl -MCPAN -e shell

I also tried to install other packages (such as DBD::DB2), but they generated the same error. I have been using the same CentOS 5.5 image for a couple of years, so it made sense to update the perl packages. Same error.

After some Google research, it appears that another error may have a similar cause.
(note the different package and line #):

Undefined subroutine &Compress::Zlib::gzopen called at /usr/lib/perl5/5.8.8/CPAN/Tarzip.pm line 122

It took a while to piece together this solution in steps, so hopefully this can save someone else a little time.

1. Install the yum utilities:

user@system> yum install yum-utils
(This contains the yum-complete-transaction executable, which does what its name says.  Description here.)

2. Get libxml2:

user@system> yum install libxml2-devel

user@system> yum-complete-transaction
(notice it's yum-, NOT the normal yum with a space)

3. Update software packages:

But use yum from the command line to do it instead of the built-in CentOS  'Software Updater'.  Run this:

user@system> yum check-update

It will outline all the available updates and ask if you want to execute them. Go ahead and say yes. There may be libraries in some of those packages that will be required to build perl modules. (In a single run, I had 242 installs and 242 removes, and it completed all of them. In my previous attempts to do the same thing from the Software Updater, the Package Manager would hang every time.)

user@system> yum-complete-transaction
(this will just make sure they're all done)

4. Run CPAN:

user@system> perl -MCPAN -e shell

Within CPAN, run these commands in this order:

cpan> force install Scalar::Util

cpan> force install IO::Compress::Base

cpan> force install Compress::Raw::Zlib

cpan> force install IO::Compress::Gzip

cpan> force install Compress::Zlib

after running all of these, CPAN should run just fine. Go ahead and download any perl packages you want.


Eric Kimminau said...
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Eric Kimminau said...
This comment has been removed by the author.
Eric Kimminau said...

I also had to add the following before Zip:
force install Compress::Raw::Bzip2

I then re-walked through all the other installs. Before adding this, every step identified that Bzip2 was missing and I had to answer "no" to have it continue without failing with an error. After adding Bzip 2 everything completed successfully.