Libguestfs - Nov 2017 - virt-customize kernel question

Hi,

I’m facing some problem trying to install some software in an image with
virt-customize.

The package I’m trying to install uses some script to check dependencies and
verifies the linux-headers-4.xxxxx are installed in the guest system.

The problem is that it uses the ‘uname –r’ command to obtain the kernel version,
and that command seems to be replying with the host kernel version instead the
guest one.

Could that be the scenario? When the image is booted, the default kernel used is
the host’s?

Is there any option (via config or something like that) to boot the image kernel
so ‘uname –r’ can provide the right info? (both host and guest are the same
architecture).

Thanks in advance!

Regards,
Andrés



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On Wed, Nov 29, 2017 at 06:04:06PM +0000, ANDRES POZO MUNOZ
wrote:
> 
> Hi,
> 
> I’m facing some problem trying to install some software in an image with
virt-customize.
> 
> The package I’m trying to install uses some script to check dependencies
and verifies the linux-headers-4.xxxxx are installed in the guest system.
> 
> The problem is that it uses the ‘uname –r’ command to obtain the kernel
version, and that command seems to be replying with the host kernel version
instead the guest one.
> 
> Could that be the scenario?
Yes, but ...
> When the image is booted, the default kernel used is the host’s?
... no.

When the libguestfs / virt-customize appliance is running it uses the
host's highest numbered kernel.  Refer to the architecture diagram
here:

  http://libguestfs.org/guestfs-internals.1.html#architecture

and the supermin manual:

  http://libguestfs.org/supermin.1.html

and run ‘virt-rescue --scratch’ to get a real idea of what's going on.

Later on, when the guest boots for real, it uses its own internal
kernel (which might not even be Linux - virt-customize can customize
Windows guests too!)
> Is there any option (via config or something like that) to boot the
> image kernel so ‘uname –r’ can provide the right info? (both host
> and guest are the same architecture).
I think you're probably better off somehow faking uname or modifying
the installation script.

However in direct answer to this question, yes it is possible to
choose a different appliance kernel by setting SUPERMIN_* environment
variables.  Note you must ‘rm -rf /var/tmp/.guestfs-`id -u`’ each time
you change the SUPERMIN_* environment variables.

  http://libguestfs.org/supermin.1.html#ENVIRONMENT-VARIABLES

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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