Tag Archives: virtualization

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 countšŸ˜¦

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virt-builder: Fedora 21 ppc64 and ppc64le images

virt-builder now has Fedora 21 ppc64 and ppc64le images available, and you can run these under emulation on an x86-64 host. Here’s how to do it:

$ virt-builder --arch ppc64 fedora-21 \
    -o fedora-21-ppc64.img

or:

$ virt-builder --arch ppc64le fedora-21 \
    -o fedora-21-ppc64le.img

To boot them:

$ qemu-system-ppc64 -M pseries -cpu POWER8 -m 4096 \
    -drive file=fedora-21-ppc64[le].img \
    -serial stdio

Oddly the boot messages will appear on the GUI, but the login prompt will only appear on the serial console. (Fixed)

Libvirt also has support, so with a sufficiently new version of the toolchain you can also use:

$ virt-install --import --name=guestname \
    --ram=4096 --vcpus=1 \
    --os-type=linux --os-variant=fedora21 \
    --arch=ppc64[le] --machine pseries \
    --disk=fedora-21-ppc64[le].img,format=raw
$ virsh start guestname

It’s quite fun to play with Big Iron, even in an emulator that runs at about 1/1000th the speed of the real thing. I know a lot about this, because we have POWER8 machines at Red Hat, and they really are the fastest computers alive, by a significant multiple. Of course, they also cost a fortune and use huge amounts of power.

Some random observations:

  1. The virt-builder --size parameter cannot resize the ppc64 guest filesystem correctly, because Anaconda uses an extended partition. Workaround is to either add a second disk or to create another extended partition in the extra space. (Fixed)
  2. The disks are ibmvscsi model (not virtio or ide). This is the default, but something to think about if you edit or create the libvirt XML manually.
  3. Somehow the same CPU/machine model works for both Big Endian and Little Endian guests. It must somehow auto-detect the guest type, but I couldn’t work out how that works. Anyway, it just works by magic. it’s done by the kernel
  4. libguestfs inspection is broken for ppc64le
  5. Because TCG (qemu software emulation) is single threaded, only use a single vCPU. If you use more, it’ll actually slow the thing down.

Thanks: Maros Zatko for working out the virt-install command line and implementing the virt-builder script to build the images.

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