[CentOS-virt] Preferred method of provisioning VM images

Tue Jun 10 16:45:45 UTC 2014
Digimer <lists at alteeve.ca>

On 10/06/14 12:21 PM, Lars Kurth wrote:
> Hi all,
> following the discussion on about documentation, I was wondering whether
> we need to look at a standard way in which we recommend how to provision
> images for VMs. Am starting this with a Xen hat, but the discussion
> should not be specific to this. There are a number of options, but all
> have some trade-offs
> == #1 virt-install ==
> Advantages: similar to KVM
> Disadvantages: may cause weird issues / confusion with people switching
> back to xl. The core issue is that with the current version of xen and
> libvirt, this only works with xm (when xl is used, this can create some
> undefined behavior). However as we have seen in some recent threads on
> this list, people tend to mix which can cause problems.
> == #2 xen-tools ==
> Advantages: Very flexible. Many other distros use xen-tools, so we have
> lots of beginners docs that just need to be tweaked
> Disadvantages: needs porting/packaging for CentOS. Does not work for
> kvm. Says "xen". (Maybe that's an advantage.)
> We know that xen-tools works with Fedora (see
> http://blog.xen.org/index.php/2013/01/24/using-xen-tools-on-fedora/), so
> the porting effort may be small
> Unknowns: What would be needed to make it work for CentOS
> == #3 virt-builder (http://libguestfs.org/virt-builder.1.html) ==
> Advantages: supports KVM, Xen and other VM inages. Seems easy to use.
> - if so, it would avoid xm / xl confusion.
> Unknowns: Not sure at which level virt-builder integrates with Xen and
> other hypervisors. It seems to operate at disk image format (similar to
> xen-tools) . I don't know whether virt-builder is restricted to some
> hypervisors in RHEL7.
> Disadvantages: may need porting/packaging for CentOS. It appears as if
> it will be in RHEL7, so it may just appear with CentOS 7. If not, some
> porting work may need to be done.
> == #4 Cloud Image from Cloud Image SIG ==
> We could rely on pre-built cloud images from the Cloud Images SIG.
> People could just download the cloud image once it's done and customize
> it, rather than installing / building their own.
> Advantages: seems easy
> Disadvantages: coordination with Cloud Images SIG. May not be flexible
> enough
> I just wanted to start a discussion about this and ask for input. This
> topic which has come up a number of times in SIG meetings as a facgtor
> influencing libvirt and other package versions.
> Regards
> Lars

I would recommend the default be the libvirtd tools, as it tries to be 
hypervisor-agnostic, so it's most portable. Also, it provides a good 
amount of flexibility for various install type, where images/docker is 
more restricted. Again, speaking about defaults/generalities.

I would, of course, point to the other tools so that users know what 
exists and what might work best for their use case.

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