A couple of my Gandi servers refused to restart the firewall due to missing modules (modules didn’t match the kernel version).
Here is a list of commands to rectify this problem.

Update modules:

• 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).old
• Uncompress the archive: tar xzf $(uname -r)-modules.tar.gz
• Then: depmod $(uname -r)
• You can list loaded modules: lsmod
• You can check all the previous version of kernel for your server here.

Referenced from here: http://wiki.gandi.net/en/iaas/references/server/kernel_modules?s[]=modules