[CentOS-virt] Automate running grub-bootxen.sh for kernel installs in Xen4CentOS

On Fri, Oct 3, 2014 at 11:57 AM, Johnny Hughes <johnny at centos.org> wrote:
> We need a way to do two things to /usr/bin/grub-bootxen.sh in Xen4CentOS.
>
> 1.  Automate running it if xen (the package) and the xen kernel are
> installed.  But only if the user WANTS to run it.
>
> 2. Allow users to automatically modify the variables passed into the
> xen.gz line (that is, more or less memory, add console settings, etc.)
> If you look at the current script, "--mbargs=dom0_mem=1024M,max:1024M
> loglvl=all guest_loglvl=all" is hard coded in as the only option for the
> xen.gz line.
>
> While doing that we also still want to preserve the ability to run that
> kernel in other places than just for xen dom0 setups.
>
> Here is how I propose we do that.
>
> Currently the /usr/bin/grub-bootxen.sh file is in centos-release-xen ...
> that is a good place as it allows us to use a different file in
> different major versions of CentOS (so the file in 7 can be different
> than the file in 6, but still use the same auxiliary files, etc).
>
> So, what we can do is setup a file in /etc/sysconfig/ (probably from the
> xen package) that we call xen-boot or xen-kernel, etc.  In this file we
> put some variables like these:
>
> BOOT_XEN_AS_DEFAULT="yes"
>
> XEN_KERNEL_MBARGS="--mbargs=dom0_mem=1024M,max:1024M loglvl=all
> guest_loglvl=all"
>
> Then we look for that file (/etc/sysconfig/xen-boot) as a post-install
> from the xen kernel.  If the file exists, we source it ... an if
> BOOT_XEN_AS_DEFAULT is yes, and if /usr/bin/grub-bootxen.sh exists we
> run it passing in XEN_KERNEL_MBARGS as a variable.
>
> The user can set BOOT_XEN_AS_DEFAULT to no if they want, so they do not
> get a xen kernel entry in their grub config.
>
> That should mean that if either there is no '/etc/sysconfig/xen-boot'
> config file OR if '/usr/bin/grub-bootxen.sh' does not exist, we get only
> the standard kernel entry .. but if they do exist, we also get a user
> modifiable xen.gz kernel entry as well.
>
> Also, we should likely use the centos-release-xen package to handle the
> '/etc/sysconfig/xen-boot' file as well, since it already has the
> /usr/bin/grub-bootxen.sh script.
>
> Thoughts?

This sounds reasonable to me.

One thing we also need to do is to make sure that when we *remove*
xen, that these grub entries are removed as well.

 -George