Everyone’s pretty eager to get on the train for cPanel 11, which is the latest production-ready release. If you are upgrading from an older version of cPanel, there are a couple things you will need to do to prepare your server:

1. Upgrade to Perl 5.8.8

Check to see what version you are currently on:

perl -v

This is perl, v5.8.7 built for i686-linux

To upgrade to 5.8.8, follow these simple steps:

wget http://layer1.cpanel.net/perl588installer.tar.gz
tar xfvz perl588installer.tar.gz
cd perl588installer
./install

You also need to check the installation of the perlmods that cPanel is more dependent on:

/scripts/realperlinstaller YAML::Syck
/scripts/realperlinstaller File::Copy::Recursive
/scripts/realperlinstaller Compress::Raw::Zlib
/scripts/realperlinstaller Scalar::Util

2. Upgrade to Maildir

The easy way of telling whether you are currently on maildir is by running the upgrade script:

/scripts/convert2maildir

If the script indicates that Maildir is not present on the system, just hit ‘1′ to start the conversion. Note that depending on the speed and size of your system, it can take several hours for this process to complete.

3.  Check your plugins

If you are running any third-party plugins (Fantastico is the most popular), you should check their documentation to make sure that they are compatible with cPanel 11 and the x3 theme.

4.  Upgrade!

When you’re ready for the upgrade, simple log into WHM and go to “Update Config” to select one of these three:

Manual Updates Only (RELEASE tree)
Manual Updates Only (CURRENT tree)
Manual Updates Only (bleeding EDGE tree)

Then just to finish the upgrade, either type /scripts/upcp from command line, or ‘Upgrade to Latest Version” from the cPanel menu in WHM.