Tag Archives: virtualization

Importing KVM guests to oVirt or RHEV

One of the tools I maintain is virt-v2v. It’s a program to import guests from foreign hypervisors like VMware and Xen, to KVM. It only does conversions to KVM, not the other way. And a feature I intentionally removed in RHEL 7 was importing KVM → KVM.

Why would you want to “import” KVM → KVM? Well, no reason actually. In fact it’s one of those really bad ideas for V2V. However it used to have a useful purpose: oVirt/RHEV can’t import a plain disk image, but virt-v2v knows how to import things to oVirt, so people used virt-v2v as backdoor for this missing feature.

Removing this virt-v2v feature has caused a lot of moaning, but I’m adamant it’s a very bad idea to use virt-v2v as a way to import disk images. Virt-v2v does all sorts of complex filesystem and Windows Registry manipulations, which you don’t want and don’t need if your guest already runs on KVM. Worst case, you could even end up breaking your guest.

However I have now written a replacement script that does the job: http://git.annexia.org/?p=import-to-ovirt.git

If your guest is a disk image that already runs on KVM, then you can use this script to import the guest. You’ll need to clone the git repo, read the README file, and then read the tool’s man page. It’s pretty straightforward.

There are a few shortcomings with this script to be aware of:

  1. The guest must have virtio drivers installed already, and must be able to boot off virtio-blk (default) or virtio-scsi. For virtio-scsi, you’ll need to flip the checkbox in the ‘Advanced’ section of the guest parameters in the oVirt UI.
  2. It should be possible to import guests that don’t have virtio drivers installed, but can use IDE. This is a missing feature (patches welcome).
  3. No network card is added to the guest, so it probably won’t have network when it boots. It should be possible to add a network card through the UI, but really this is something that needs to be fixed in the script (patches welcome).
  4. It doesn’t handle all the random packaging formats that guests come in, like OVA. You’ll have to extract these first and import just the disk image.
  5. It’s not in any way supported or endorsed by Red Hat.

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How to rebuild libguestfs from source on RHEL or CentOS 7

Three people have asked me about this, so here goes. You will need a RHEL or CentOS 7.1 machine (perhaps a VM), and you may need to grab extra packages from this preview repository. The preview repo will go away when we release 7.2, but then again 7.2 should contain all the packages you need.

You’ll need to install rpm-build. You could also install mock (from EPEL), but in fact you don’t need mock to build libguestfs and it may be easier and faster without.

Please don’t build libguestfs as root. It’s not necessary to build (any) packages as root, and can even be dangerous.

Grab the source RPM. The latest at time of writing is libguestfs-1.28.1-1.55.el7.src.rpm. When 7.2 comes out, you’ll be able to get the source RPM using this command:

yumdownloader --source libguestfs

I find it helpful to build RPMs in my home directory, and also to disable the libguestfs tests. To do that, I have a ~/.rpmmacros file that contains:

%_topdir	%(echo $HOME)/rpmbuild
%_smp_mflags	-j5
%libguestfs_runtests   0

You may wish to adjust %_smp_mflags. A good value to choose is 1 + the number of cores on your machine.

I’ll assume at this point that the reason you want to rebuild libguestfs is to apply a patch (otherwise why aren’t you using the binaries we supply?), so first let’s unpack the source tree. Note I am running this command as non-root:

rpm -i libguestfs-1.28.1-1.55.el7.src.rpm

If you set up ~/.rpmmacros as above then the sources should be unpacked under ~/rpmbuild/SPECS and ~/rpmbuild/SOURCES.

Take a look at least at the libguestfs.spec file. You may wish to modify it now to add any patches you need (add the patch files to the SOURCES/ subdirectory). You might also want to modify the Release: tag so that your package doesn’t conflict with the official package.

You might also need to install build dependencies. This command should be run as root since it needs to install packages, and also note that you may need packages from the repo linked above.

yum-builddep libguestfs.spec

Now you can rebuild libguestfs (non-root!):

rpmbuild -ba libguestfs.spec

With the tests disabled, on decent hardware, that should take about 10 minutes.

The final binary packages will end up in ~/rpmbuild/RPMS/ and can be installed as normal:

yum localupdate x86_64/*.rpm noarch/*.rpm

You might see errors during the build phase. If they aren’t fatal, you can ignore them, but if the build fails then post the complete log to our mailing list (you don’t need to subscribe) so we can help you out.

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KVM Forum 2015

Assuming HMG can get my passport back to me in time, I am speaking at the KVM Forum 2015 in Seattle USA (full schedule of talks here).

I’m going to be talking about virt-v2v and new features of qemu/KVM that made it possible for virt-v2v to be faster and more reliable than ever.

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libguestfs works on MIPS Creator (mipsel)

[Previous post about the MIPS Creator CI20]

Slowly, of course.

I had to compile supermin & qemu from upstream and download (but not install) a qemu-compatible Debian kernel. Then setting the following environment variables allows make quickcheck to pass:

$ cat localenv
export SUPERMIN=/home/rjones/d/supermin-mipsel/src/supermin
export LIBGUESTFS_HV=/home/rjones/d/qemu-mipsel/mipsel-softmmu/qemu-system-mipsel
export SUPERMIN_KERNEL=/home/rjones/d/libguestfs-mipsel/kernel/boot/vmlinux-3.16.0-0.bpo.4-4kc-malta
export SUPERMIN_KERNEL_VERSION=3.16.0-0.bpo.4-4kc-malta
export SUPERMIN_MODULES=/home/rjones/d/libguestfs-mipsel/kernel/lib/modules/3.16.0-0.bpo.4-4kc-malta/

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virt-builder Debian 8 (Jessie) image

Debian 8 was released a couple of days ago, and you can now install it through virt-builder.

Use --notes to read the release notes:

$ virt-builder debian-8 --notes

To build an image:

$ virt-builder debian-8 \
    --firstboot-command "dpkg-reconfigure openssh-server"

To boot it under libvirt:

$ virt-install --import \
  --name debian-8 --ram 2048 \
  --disk path=debian-8.img,format=raw --os-variant=debianwheezy

(At some point --os-variant=debianjessie will work, but virt-install doesn’t support it yet)

Update: This is how I ended up running Debian 8:

$ virt-builder debian-8 \
    --size=30G \
    --root-password PASSWORD \
    --edit '/etc/apt/sources.list: s/wheezy/jessie/g' \
    --run-command '
      apt-get -y install debian-keyring debian-archive-keyring
      apt-key update
    ' \
    --install emacs,nfs-common,sudo \
    --edit '/etc/ssh/sshd_config:
              s/^#PermitEmptyPasswords no/PermitEmptyPasswords yes/' \
    --firstboot FIRSTBOOT.sh
    --run-command 'update-rc.d virt-sysprep-firstboot defaults' \
    --run-command 'killall dbus-daemon cgmanager ||:'

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New in virt-v2v

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Video: virt-v2v integration with RHEV-M

This video shows using the GUI to import a virtual machine from VMware to RHEV-M. It performs the conversion using virt-v2v, which is responsible for installing virtio drivers, fixing the bootloader, and so forth.

Thanks Arik Hadas. Now I just have to fix the epic RHEL 7.2 bug list — 57 bugs at last count 😦

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