Audience:
 - libvirt developers

Interested in:
 - what it is
 - new developments

[---- OVERVIEW ----]

Libguestfs is a C library for accessing and creating
disk images.  It has been in development for four and a half
years, is very mature, and is used in many large projects
such as: virt-v2v, OpenStack, 

Like libvirt, the C API is long term stable so a program
written against the API four years ago will still work today.

There are bindings in lots of programming languages.
Here is an example of a Python program using the API to create a
partitioned disk image with some content from a tar file.

Show create.py

Run create.py

virt-filesystems -a disk.img --all --long -h

virt-df -a disk.img -h

guestfish --ro -a disk.img -m /dev/sda1 find /






[---- TOOLS ----]


We have a lot of tools associated with libguestfs:

virt-<TAB>

Pick a few.

Today I want to just mention virt-builder which is a tool
for rapidly and safely customizing templates of virtual
machines.

virt-builder -l

virt-builder fedora-19 \
  --hostname f19.example.com \
  --firstboot-install nmap \
  --edit '/etc/yum.conf: s/gpgcheck=1/gpgcheck=0/'


[---- LIBVIRT INTEGRATION ---]

How libguestfs uses libvirt:

Behind the scenes we create a captive appliance.  Since Fedora 18 &
RHEL 7, we use libvirt to manage the appliance and sVirt to protect
the host from rogue filesystems.


Our use of libvirt APIs is very simple:
 - virConnect*
 - "lifecycle APIs" like virDomainCreateXML
 - libvirt XML
 - hotplugging APIs
 - capabilities

What we DON'T care about:

 - live migration
 - stable guest ABI
 - storage APIs
 - snapshots
 - NUMA

Bugs in libvirt:

 - Tracker: 910269
 - <cpu mode="host-model"> (WORKAROUND)
 - qemu: could not load kernel ... Permission denied
 - libvirt doesn't label backing sockets, eg. qcow2 using NBD backing
 - could not destroy libvirt domain: Requested operation is not valid: domain is not running
 - libvirt chown's <kernel> file to root, but doesn't restore ownership
 - XML error: No PCI buses available (FIXED)
 - This QEMU doesn't support virtio scsi controller (qemu bug: FIXED)
   (example of non-obvious error message)
 - TMPDIR / environment variable handling is broken (WORKAROUND)

Missing features in libvirt:

 - labelling backing sockets
 - no way to specify net= parameter to qemu
 - unnamed guests

Things we don't like:

 - error messages are confusing, real information is hidden
 - logging/debugging is hard
 - fragile
 - regressions
 - essentially impossible to use libvirt/sVirt on anything except Fedora/RHEL

Things we like:

 - sVirt
 - having someone else deal with qemu
 - hotplugging