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Re: [Xen-users] snapshot - backup for xen vm's

Nico Kadel-Garcia wrote:
> Fajar A. Nugraha wrote:
>>> Unfortunately, that piece of over-hyped installatiion obscurity known
>>> as libvirt does not allow you options to do this, and mandates the use
>>> of pygrub. This means that you must have a /dev/xdva device, and grub
>>> itself only works if you have a disk, not if you only have partitions.
>>>     
>> pygrub works perfectly with partition-only setup (at least on RHEL5).
>>   
> Pygrub doesn't read the MBR off of the para-virtualized image?
>
No. Grub does, pygrub doesn't. Pygrub simply checks the presence of
/boot/grub/menu.lst on domU and reads it. You don't need to have grub
installed on domU to have pygrub work, you just need that file.

> I've used the "jailtime" tarballs for CentOS: they're fairly
> reasonable, but are cluttered with disk images rather than simply
> providing a tarball and letting the installer set up their own
> partitions.
>
I see. I haven't used those (partly because I don't need to).
My tarball simply contains the content of domU root fs. You still need
to setup the partitions manually. This was the best option for me
(compared to disk images, virt-manager, yum --installroot, etc.) but it
might not be suitable for everybody.
>>>  It's also very, very helpful to have enough disk in the partiton to
>>> mirror the *whole* RedHat or Fedora installation directory.     
>> I'm not sure what you mean here. I'd prefer to have a local copy of yum
>> repository (including RH installation directory). It's on local network,
>> accessed via http, but it doesn't have to be on dom0. That way it scales
>> well if you have lots of dom0s.
>>   
> Mirror the whole RedHat DVD or network install site. Copy it to local
> disk on the domain creating machine: you want this all to happen on
> local disk, *NOT* over a network! Make a new partition, and mount it.
> Copy the whole thing over to /var/cache/yum/base/packages and work
> from there to install whatever you want, usually with yum. Do an
> alternative root directory RPM or Yum installation into that
> directory. But using yum, it downloads the files: it's vastly faster
> to simply copy them over and use a "file:///" based URL, rather than
> the classic HTTP or FTP URL's. be already available or wind up
> downloaded into /var/cache/yum in the target directory, but you have a
> huge advantage in being able to do the updates or add-on packages at
> OS image install time, rather than wending your way through
>
In my setup I use a local yum repository via http.
I have several installation methods, actually :
- for PV domUs : use tar.gz templates.
- for HVM domUs and physical machine : Use custom RH installer, either
via CD/DVD or network (PXE) install.

The tar.gz fast is signifcantly faster than rpm-based install (including
yum --installroot), even when the RPMS is on local disk (I tried this
before), partly due to the fact that RPM needs extra steps (dep
resolution, pre/post install scripts, etc.) other than simply writing
files like the tar.gz. It has all necessary add-on packages included.
You still need to do a "yum-upgrade" afterwards, but the total time
required is still a lot faster.

The custom RH installer is basically the standard RHEL 5 installer with
a kickstart file that adds additional yum repository and installs some
local packages. It check files from CD/DVD (if available) and network
repository, chooses the newest version, and performs the installation.
This way it performs updates and installs add-on packages at OS image
install time. The CD/DVD is created from an ISO image that is updated
weekly to contain only the newest packages in addition to add-on
packages. You still get newest packages at install time even if you use
an old DVD since it will automatically compare the local version with
the one on network repository and choose whichever is newest.

Network BW is not an issue since I'm working on local, 1Gbps network.
Besides, "Mirror the whole RedHat DVD or network install site. Copy it
to local disk on the domain" would use up that BW anyway. Again, this
was the best option for me but it might not be suitable for everybody.

Regards,

Fajar

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