FWN/Beats/Virtualization

Virtualization

In this section, we cover discussion on the @et-mgmnt-tools-list, @fedora-xen-list, and @libvirt-list of Fedora virtualization technologies.

Contributing Writer: Dale Bewley

Fedora Virtualization List

This section contains the discussion happening on the fedora-virt list.

New Release libguestfs 1.0.10

Richard Jones announced release 1.0.10 of libguestfs Born only a couple of weeks ago(FWN#171), libguestfs has progressed very far very fast.

"libguestfs is a library for accessing and modifying guest disk images. Amongst the things this is good for: making batch configuration changes to guests, getting disk used/free statistics (see also: virt-df), migrating between virtualization systems (see also: virt-p2v), performing partial backups, performing partial guest clones, cloning guests and changing registry/UUID/hostname info, and much else besides."

Features in 1.0.10 include:

• bindings for: C, C++, Perl, Python, OCaml, Ruby, Java and shell scripting
• KVM support
• QEMU binary is completely configurable at compile & runtime
• ext4 support
• support for uploading and downloading arbitrary-sized files
• support for uploading and downloading tar and tar.gz content
• support for querying size of block devices, setting r/o
• support for reading ext2/3 superblocks
• stat, lstat, statvfs commands
• commands to mount filesystems read-only
• run arbitrary commands from the guest
• file(1) command
• readline in guestfish with history and tab completion
• guestfish 'edit' command
• big documentation improvements, including more on the internals
• pkgconfig file

Richard posted some example uses of the libguestfs command line tool called guestfish.

Non-root User Image Locations

Robert Day asked "by default, new VM images are created in /var/lib/libvirt/images, and that directory is not accessible to non-root users."

Daniel Berrange

There are two classes of libvirt driver connection

 - Privileged, per-host connections
 - Unprivileged, per-user connections

Xen provides a per-host connection. UserModeLinux and QEMU provide 
both (qemu:///system and qemu:///session). VirtualBox just proivides
a per-user instance (vbox:///session) and so on.

Now by default in Fedora, when connecting to QEMU, virt-manager will
use the privileged per-host connection, so VMs end up in the system
directory /var/lib/libvirt/images.

Our goal (perhaps for F12) should be for local desktop virt use
cases to use the unprivileged  QEMU connection qemu://session
by default, and have VM disk images stored in your home directory

> How would we allow KVM access? Unix groups or something else?

Two options

 - A UNIX group for /dev/kvm
 - Just make it world writable


In theory now KVM no longer pins all guest RAM into host RAM, it is 
reasonable safe to allow users to access it without any restrictions.
(eg option 2) Will need to confirm with KVM developers if this is 
really so, but that was the intention last time i asked them.

Historically SELinux has wanted images in particular locations. With
the introduction of SVirt in libvirt, we have much more advanced
SELinux integration and will in fact automatically re-label images
to match the needs of a VM. So allowing arbitary locations *and*
still being in compliance with SELinux policy is now practical

Fedora Xen List

This section contains the discussion happening on the fedora-xen list.

Dom0 Kernel Not Before 2.6.31

The upstream Xen dom0 work done by Jeremy Fitzhardinge has been cleaned up and reorganized into

• xen-tip/master - Known-working branch, with only tested changes
• xen-tip/next - Current bleeding edge; should at least compile

Michael Young built a new experimental dom0 kernel "version (2.6.30-0.1.2.21.rc3.xendom0.fc12) is based on the Fedora devel kernel branch and xen-tip/next branch from the pvops kernel repository." This kernel may be found in Michael's yum repo.

Michael added that "very few xen patches made it into 2.6.30, just bugfixes and tidy ups, so we are waiting at least until 2.6.31 for mainline dom0 support."

Libvirt List

This section contains the discussion happening on the libvir-list.

New Release libvirt 0.6.3

Daniel Veillard announced a new libvirt release, version 0.6.3.

"The main points are the VirtualBox driver and a number of bug fixes." Read the post for details of other changes.

New features:

• VirtualBox driver support (Pritesh Kothari)
• virt-xml-validate new command (Daniel Berrange)

Improvements:

• add SCSI storage rescan (David Allan)
• rootless LXC containers support improvements (Serge Hallyn)
• getHostname support for LXC (Dan Smith)
• cleanup and logging output of some domain functions (Guido Gunther)
• drop pool lock when allocating volumes (Cole Robinson)
• LXC handle kernel without CLONE_NEWUSER support (Serge Hallyn)
• cpu pinning on defined Xen domains (Takahashi Tomohiro)
• dynamic bridge names support (Soren Hansen)
• LXC use of private /dev/pts when available (Daniel Berrange)
• virNodeDeviceCreateXML and virNodeDeviceDestroy entry points (Dave Allan)

Daniel Veillard followed the announcement with a roadmap suggesting "a new release around May 25, which would mean entering code feature freeze around May 18". Version 0.6.2 was released April 3rd (FWN#170).