In this article we will show you how to install Xen 4.1.1 to your system with a custom dom0 Linux kernel.
1. Preparation
2. Installation
1. Preparation
In order to successfully build and run Xen we need to download and install some tools and utilities. To install them in Debian Squeeze we run the following command as root:
root@dom0$ apt-get install bcc bin86 gawk bridge-utils iproute libcurl3 libcurl4-openssl-dev bzip2 module-init-tools transfig tgif texinfo texlive-latex-base texlive-latex-recommended texlive-fonts-extra texlive-fonts-recommended pciutils-dev mercurial build-essential make gcc libc6-dev zlib1g-dev python python-dev python-twisted libncurses5-dev patch libvncserver-dev libsdl-dev libjpeg62-dev iasl libbz2-dev e2fslibs-dev git-core uuid-dev ocaml libx11-dev bison flex xz-utils ocaml-findlib
If you have a 64 bit version of Debian/Ubuntu you also need this additional package:
root@dom0$ apt-get install gcc-multilib
To be able to use other operating systems than Linux/ FreeBSD as a guest (e.g. Windows) our hardware must has support for VT (Virtualization Technology). Hardware assisted virtualization offers new instructions to support direct calls by a paravirtualized guest/driver into the hypervisor, typically used for I/O or other hypercalls. The main idea behind this is to introduce a new privilege level, called the level -1 below the level 0. The VMM can run on this new level. By introducing this new level, the guest operating systems can run at level 0 without any modifications and the hardware requests they perform can be captured directly from the system. To check if our Intel based system supports this feature we can run:
root@dom0$ cat /proc/cpuinfo | grep vmx
For AMD based processors, we can run the following command:
root@dom0$ cat /proc/cpuinfo | grep svm
2. Installation
We are now ready to download and install Xen. In this guide we will use the version 4.1.1 of Xen. To get the source code we run:
user@dom0$ wget http://bits.xensource.com/oss-xen/release/4.1.1/xen-4.1.1.tar.gz
Now we can extract it and build it:
user@dom0$ tar xvf xen-4.1.1.tar.gz
user@dom0$ cd xen-4.1.1
user@dom0$ make xen
user@dom0$ make tools
user@dom0$ make stubdom
After the build has completed we should have a top-level directory called ‘dist’ in which all resulting targets will be placed. To install them on our system we run:
root@dom0$ make install-xen
root@dom0$ make install-tools PYTHON_PREFIX_ARG=
root@dom0$ make install-stubdom
At this point Xen and its utilities are installed on our system. We should have the following files in ‘/boot’ directory:
/boot/xen.gz
/boot/xen-4.gz
/boot/xen-4.1.gz
/boot/xen-4.1.1.gz
Now, in the file ‘/etc/xen/xend-config.sxp’ we enable the following option:
(xend-unix-server yes)
And finally, to enable automatic start of Xen related services on system startup we run:
root@dom0$ update-rc.d xencommons defaults 19 18
root@dom0$ update-rc.d xend defaults 20 21
root@dom0$ update-rc.d xendomains defaults 21 20
root@dom0$ update-rc.d xen-watchdog defaults 22 23
3. Creating and installing a dom0 kernel
At this point Xen is built and installed on our system but it is not ready for use, as we don’t have a dom0 kernel yet. The kernel with which our system booted will not work with Xen. So, we are going to compile a dom0 kernel.
There are two different types of Xen dom0 capable kernels available today:
- pvops (paravirt_ops) kernels, featuring new rewritten Xen support based on the upstream (kernel.org) Linux pvops framework. This work has been included in upstream kernel.org kernel since Linux 2.6.37. Pvops is a piece of Linux kernel infrastructure to allow it to run paravirtualized on a hypervisor. This feature allows us to build a single Linux kernel binary which will either boot native on bare hardware, or boot fully paravirtualized as a Xen dom0 or domU.
- xenlinux kernels based on the “old” patches originally for Linux 2.6.18. These Xenlinux patches won't be integrated to upstream Linux.
In this guide we will use the latest stable Linux kernel which is 3.0.4 and has build-in support for pvops. The first thing to do is to grab the kernel from kernel.org:
user@dom0$ tar xvf linux-3.0.4.tar.gz
Now, we can configure our new kernel by running:
user@dom0$ make menuconfig
We must be sure that we have a correct Processor family set in the kernel configuration. Xen dom0 options won’t show up at all if we have too old CPU selected. If we are building a 32 bit version of the kernel we need to enable PAE support:
Processor type and features →
High memory support (64GB)
PAE (Physical Address Extension) Support - enabled
Note that PAE is not needed for 64 bit kernels. Also, if we are building a 32 bit kernel we need to set the option ‘CONFIG_HIGHPTE=n’:
Processor type and features →
Allocate 2nd-level pagetables from highmem - disabled
Furthermore, Xen Dom0 support depends on ACPI support on both 32 and 64 bits versions of the Linux kernel. Thus, we must enable ACPI support during configuration:
ACPI (Advanced Configuration and Power Interface) Support - enabled
Below, is a list of options needed to compile Linux kernel with dom0 support:
CONFIG_ACPI_PROCFS=y
CONFIG_XEN=y
CONFIG_XEN_MAX_DOMAIN_MEMORY=32
CONFIG_XEN_SAVE_RESTORE=y
CONFIG_XEN_DOM0=y
CONFIG_XEN_PRIVILEGED_GUEST=y
CONFIG_XEN_PCI=y
CONFIG_PCI_XEN=y
CONFIG_XEN_BLKDEV_FRONTEND=y
CONFIG_XEN_NETDEV_FRONTEND=y
CONFIG_XEN_KBDDEV_FRONTEND=y
CONFIG_HVC_XEN=y
CONFIG_XEN_FBDEV_FRONTEND=y
CONFIG_XEN_BALLOON=y
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_XEN_DEV_EVTCHN=y
CONFIG_XEN_GNTDEV=y
CONFIG_XEN_BACKEND=y
CONFIG_XEN_BLKDEV_BACKEND=y
CONFIG_XEN_NETDEV_BACKEND=y
CONFIG_XENFS=y
CONFIG_XEN_COMPAT_XENFS=y
CONFIG_XEN_XENBUS_FRONTEND=y
CONFIG_XEN_PCIDEV_FRONTEND=y
To enable these options we can select the following additional fields during configuration:
Processor type and features →
Paravirtualized guest support [y] →
Xen guest support – enabled
Bus oprions (PCI etc.)→
Xen PCI frontend – enabled
Device Drivers →
Block Devices [*] →
Xen virtual block device support – enabled
Block-device backend driver – enabled
Network device support [*] →
Xen network device frontend driver – enabled
Xen backend network device – enabled
Input device support →
Miscellaneous devices →
Xen virtual keyboard and mouse support – enabled
Character devices →
Xen Hypervisor console support – enabled
Xen driver support →
Xen memory balloon driver – enabled
Scrub pages before returning them to system – enabled
Xen /dev/xen/evtchn device Backend driver support – enabled
Xen filesystem – enabled
Create compatibility mount point /proc/xen – enabled
Create xen entries under /sys/hypervisor – enabled
userspace grant access device driver – enabled
User-space grant reference allocator driver – enabled
xen platform pci device driver – enabled
Now, we can build and install the kernel:
user@dom0$ make
root@dom0$ make modules_install
root@dom0$ make install
root@dom0$ cd /boot
root@dom0$ mkinitramfs -o initrd.img-3.0.4 3.0.4
root@dom0$ update-grub
We can now reboot our system to the Xen enabled 3.04 Linux kernel. To verify that Xen is running we can do the following:
root@dom0$ cat /proc/xen/capabilities
The output must be same as the following line:
control_d
This tells us that we have booted in a Xen control domain (dom0). Also, to verify that our Xen environment is working properly we can run:
root@dom0$ xm info
root@dom0$ xm list
If the output of these commands is the expected we have successfully installed Xen to our system. For example, ‘xm list’ command should list our dom0 domain:
Name ID Mem VCPUs State Time(s)
Domain-0 0 1895 2 r----- 419.0
4. References
- David Chisnall: The Definitive Guide to the Xen Hypervisor. Prentice Hall, 2007
- XenParaVirtOps [http://wiki.xensource.com/xenwiki/XenParavirtOps#head-6a64160b847b6fbd780350181436269c5a0a5b11]
- The Linux Kernel Archives [http://www.kernel.org/]
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Get the full pdf here: http://www.cs.uoi.gr/~gkappes/tutorials/xen_guide.pdf
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