Ubuntu – Xen 4.4 (64-bit) is not working on Ubuntu 14.04, xl fails

14.0464-bitvirtualizationxen

I did a fresh install of Ubuntu 14.04 Desktop 64-bit with LVM option selected during installation. Then the first thing I did was installation of xen hypervisor.

sudo apt-get install xen-hypervisor-4.4-amd64

I rebooted into this main Ubuntu once. Then I rebooted into Ubuntu with Xen hypervisor. When I try to do anything with the default toolstack xl, it gives an error.

# xl info xc: error: Could not obtain handle on privileged command interface (2 = No such file or directory): Internal error libxl: error: libxl.c:87:libxl_ctx_alloc: cannot open libxc handle: No such file or directory cannot init xl context

Seems this problem has been there in various versions of xen and have been sorted out time to time in upgrades but there is no clear instruction set to use in my case, Xen 4.4. Any clear help will be appreciated.

NOTE: I am doing all this on a 64-bit virtual machine in Virtualbox, obviously my processor (both original and virtual) support virtualization in hardware, and this is enabled.

Best Answer

I know it is a bit late but I had the same problem (except I installed xen 4.5).

I solved the issue by running

/etc/init.d/xencommons start

at every startup.

Hope this can help someone.

The Answer

The XAPI toolstack is not dead. It is in active development here: https://github.com/xapi-project/xen-api

However, xapi never really ran right(imo) on debian derivatives. That has been changing since xen became a linux foundation project. If you really want xapi on debian, then I'd recommend you compile the xenserver core referenced in the xen-api github readme.

There are a couple of things you need to know..

First, some terminology,

The Xen Hypervisor is the thin layer that domains (or vms, referred to as dom0 or domu) talk to when they want resources. It is now part of the linux kernel, so it no longer requires a custom kernel to run. The hypervisor does not have a shell or any easy way to mess with it directly. It is generally configured and managed from a SPECIAL vm we call dom0, on which the toolstack is installed.

The Toolstack is a set of programs used to manage all domains on a host and to generally tell the Xen Hypervisor what to do. As you know, the primary toolstacks of choice are xe(XAPI/XCP), xl(xenlight/libxl), and xm(xend).

There exist other tools that talk to the various toolstacks and provide another layer of abstraction. The most well known of these is libvirt.

Not too long ago(ok, maybe awhile ago), xen hypervisor development was taken over by the linux foundation, which opened up a lot of doors as far as development was concerned. The most important things that you need to know are:

xm is going away. This limits your future-proof toolstack choices to xl(libxl) or xapi.
The xapi toolstack is working towards building xapi on top of libxl.

Ok, now to the effectively useful information. The differences between libxl and xapi.

xenlight, libxl, the xl toolstack

The xl toolstack is effectively a command line tool to manage the xen hypervisor. It generally is given a vm .cfg file like the ones in the ubuntu archive (http://archive.ubuntu.com/ubuntu/dists/trusty/main/installer-amd64/current/images/netboot/xen/xm-debian.cfg) and turns them into running vms via xl create .

It doesn't manage the creation of filesystems on iscsi targets or lvm systems. It is pretty dead simple and if you are starting with xen, it is imho the best place to get started as you can get a feel for what xen is doing and why. Additionally, the config files are human readable plain text, and when something is misconfigured it's easy to figure out how.

Here are some useful xl commands:

xl list
xl console
xl info

xe, xapi, XCP(misnomer, XCP is now known as XenServer, which is a full distro)

The xapi toolstack makes scaling xen vm deployment trivial. There are two parts to xapi, the xe command line tool and the xapi api which is accessible via rpc via a web interface. XAPI is what XenCenter talks to and is a fundamentally different experience from the simplicity of xl. With xapi, there are tools for managing lvm partitions, snapshots, remote storage, advanced networking, performance statistics, patches, etc etc etc.

It is much much more than a hypervisor toolstack in that it manages all parts of the host system. If you want to get used to xapi, the best route is to install Citrix XenServer and manage it from XenCenter. Once you get a feel for the GUI, ssh into your XenServer and start playing with the xe command. Everything, including the uuids that are associated with vms, are tab-completable and the help documentation is fairly complete.

The End

If you have more questions you can email me at b@ethe.us

Ubuntu – xen hypervisor wont boot from grub and “Can’t find hypervisor information in sysfs!” error ubuntu 14.04

Although the community wiki states that as of Ubuntu 14.04, GRUB will automatically choose to boot Xen first if Xen is installed, it doesn't if you don't run Ubuntu (16.04) in English.

To be able to select the right kernel at boot open /etc/default/grub

sudo nano /etc/default/grub

and comment out the following 2 lines by putting a # in front of it and set GRUB_TIMEOUT to let's say 5

#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=5

next update Grub and reboot

sudo update-grub
sudo shutdown -r now

You should now be able to to select the right kernel in the grub menu and boot your system with Xen enabled. If you want to boot your system with this kernel by default write down the translation of "Ubuntu GNU/Linux, with Xen hypervisor". In my case (Dutch) that's "Ubuntu GNU/Linux, met Xen-hypervisor" and open /etc/default/grub.d/xen.cfg when booted.

sudo nano /etc/default/grub.d/xen.cfg

Replace GRUB_DEFAULT="Ubuntu GNU/Linux, with Xen hypervisor" with GRUB_DEFAULT="translation" at the bottom of that file and undo the changes you made in /etc/default/grub. Update Grub again and reboot with Xen enabled by default ...