[CentOS-virt] Testing new Xen Version and rollback.

Christopher G. Stach II cgs at ldsys.net
Fri Oct 9 01:17:30 UTC 2009

----- "Ben M." <centos at rivint.com> wrote:

> I do not have a comprehensive grasp on startup scripts, as well as
> what files are not rolled into the kernel itself.
> In other words, I don't understand yet when a new kernel is installed,
> whether there are any support files that come with it, or whether 
> everything that, for instance, the Xen kernel needs, are entirely
> within that kernel file (hardware drivers).

Kernels in major distros are usually distributed with most drivers compiled as modules in a package that contains those modules and an initrd, or script that makes an initrd, that contains the drivers necessary to boot your system. This isn't always the case, as drivers may be compiled right into the kernel or they may be completely excluded for whatever reason (mini distros, appliances).

After booting, depmod resolves the kernel module dependencies in /lib/modules/<kernel version> only for the kernel that is currently running. As long as you don't install a kernel package that has the same version string (e.g., 2.6.18-128.4.1.el5xen) as a kernel you care about, you have nothing to worry about. If someone is distributing third party kernel packages that collide with a major distribution's without a really good reason, you should probably avoid using their packages altogether.

> If it is just a matter of having a section for it in grub.conf.

Many kernel packages will set up grub.conf for you. If it's just a tarball, you will have to do this manually. You may also need to build a new initrd.

Christopher G. Stach II

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