In order to update your server's modules, you need to:
Change directory to root: cd /
Download the modules' archive: wget http://mirrors.gandi.net/kernel/$(uname -r)-modules.tar.gz
Move the existing modules: mv -f /lib/modules/$(uname -r) /lib/modules/$(uname -r).ancien
Uncompress the archive: tar xzf $(uname -r)-modules.tar.gz
Then : depmod $(uname -r)
If you are upgrading a module, you might want to list loaded modules: lsmod
Test the presence of the new module: modinfo your_module . For example: modinfo ipv6 returns with the information field of the module.
If everything went well, delete the old directory: rm -rf /lib/modules/$(uname -r).ancien and remove the downloaded file rm /$(uname -r)-modules.tar.gz
If needed, reload the module rmmod your_module ; modprobe your_module to use the new version
Your modules are now available.
The core currenlty used for virtual servers is 2.6.18-xenU. This core may change with the future versions. Please remember to check the version of the core used on your virtual server before starting the download of the modules' archive.
You can check all the previous version of kernel for your server here.