Xen 03 - domU

category: learnz/xen · date: 2008-01-09 · source: old.linuxor.sk/VIRTUALIZATION/BASIC/BH_Debian4.0_XEN_domU.txt · theme: github

Xen on Debian 4 Learning · Previous: dom0 · Next: domU - backup with LVM snapshots

The Slovak original of this document: Xen 03 - domU (slovensky).

asciiart

|=----------------------------------=[ XEN ]=------------------------------=|
+---------------------------------------------------------------------------+
|                                                                           |
|                               XEN - domU (vmware)                         |
|                                 Debian 4.0 Etch                           |
|                                                                           |
+---------------------------------------------------------------------------+
|=-------------------------------=[ BH 2007 ]=-----------------------------=|

1. Creating a new virtual machine (LVM)

asciiart

        Install the utilities for managing xen hosts
        --------------------------------------------
        # apt-get install xen-tools

        Set the parameters the new VM host needs
        # nano /etc/xen-tools/xen-tools.conf
        ------------------------------------
        lvm         = nejaka_volume_group
        debootstrap = 1

        size   = 3Gb
        memory = 64Mb
        swap   = 128Mb
        fs     = ext3
        dist   = etch

        gateway   = 10.62.1.1
        netmask   = 255.255.0.0

        passwd = 1

        kernel = /boot/vmlinuz_nejake_jadro_v_boot
        e.g. /boot/vmlinuz-2.6.18-5-xen-686
        initrd = /boot/initrd_nejaky_initrd_v_boot
        e.g. /boot/initrd.img-2.6.18-5-xen-686
        ------------------------------------END-/etc/xen-tools/xen-tools.conf

        Create a VM host named www.vhosts.example with the IP address 10.62.2.45
        ------------------------------------------------------------------------
        # xen-create-image --ip=10.62.2.45 --hostname=www.vhosts.example

        Start the newly created VM host and switch to its console (-c)
        --------------------------------------------------------------
        # xm create -c www.vhosts.example.cfg

        Install 2 packages to prevent warnings from APT
        -----------------------------------------------
        # apt-get install locales console-data

        Configure the locales package
        -----------------------------
        # dpkg-reconfigure locales

        Leaving the virtual machine console
        -----------------------------------
        CTRL + ]

        Returning to the virtual machine console
        ----------------------------------------
        # xm console www.vhosts.example

        Shutting down the virtual machine
        ---------------------------------
        # xm shutdown -H www.vhosts.example

        Destroying the virtual machine [destroy] (!!! does not do a clean shutdown !!!)
        -------------------------------------------------------------------------------
        # xm destroy www.vhosts.example

        To have the virtual machine start when the dom0 machine boots
        -------------------------------------------------------------
        # mkdir /etc/xen/auto
        # ln -s /etc/xen/www.vhosts.example.cfg /etc/xen/auto/

2. Setting up the network (routed network)

asciiart

----
dom0
----

        # nano /etc/xen/xend-config.sxp
        -------------------------------
        (network-script network-route)
        (vif-script vif-route)

-----------
www.vhosts.example
-----------

        # nano /etc/xen/www.vhosts.example.cfg
        -------------------------------
        vif  = [ 'ip=10.62.2.45' ]

---------------------------------------------------
workstation (from which I connect to dom0 and domU)
---------------------------------------------------

        # route add 10.62.2.45 gw 10.62.2.44

3. Setting up the network (NAT-ed network)

asciiart

----
dom0
----

        # nano /etc/xen/xend-config.sxp
        -------------------------------
        (network-script network-nat)
        (vif-script vif-nat)

        Enable SNAT for the network 192.168.1.0/24
        ------------------------------------------
        # iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -j SNAT --to-source 10.62.2.44

        Redirect requests for 10.62.2.44:2222 to 192.168.1.2:22
        -------------------------------------------------------
        # iptables -t nat -A PREROUTING -p tcp -s 10.62.2.22 -d 10.62.2.44 --dport 2222 -j DNAT --to-destination 192.168.1.2:22

        Redirect requests for 10.62.2.44:80 to 192.168.1.2:80
        -----------------------------------------------------
        # iptables -t nat -A PREROUTING -p tcp -s 10.62.2.22 -d 10.62.2.44 --dport 80 -j DNAT --to-destination 192.168.1.2:80

-----------
www.vhosts.example
-----------

        # nano /etc/xen/www.vhosts.example.cfg
        -------------------------------
        vif  = [ 'ip=192.168.1.2' ]

Notes
------

iptables -t nat -A PREROUTING -m physdev --physdev-in vif1.0 -p tcp -s 10.62.2.45 -d 10.62.2.44 --dport 8080 -j DNAT --to-destination 10.62.1.1:8080
iptables -t nat -A POSTROUTING -m physdev --physdev-out vif1.0 -p tcp -s 10.62.2.45 -d 10.62.1.1 --dport 8080 -j SNAT --to-source 10.62.2.44

create the logical partition 'xen1' for the first virtual machine
-----------------------------------------------------------------
# lvcreate -L 2G -n xen1 nejaka_volume_group

        RAID1
        -----
        disk1 -|
               |- LVM (VG-system - system partitions for the virtual machines)
        disk2 -|
        -----
        /dev/system/www.vhosts.example-disk
        /dev/system/www.vhosts.example-swap

        RAID1
        -----
        disk1 -|
               |- LVM (VG-data - data partitions for the virtual machines)
        disk2 -|
        -----
        /dev/data/www.vhosts.example-usr
        /dev/data/www.vhosts.example-local
        ...

DISKS

asciiart

        If we use a single partition
        ----------------------------
        disk = [ 'phy:/dev/hdX,hda1,w' ]

        If we use several partitions
        ----------------------------
        disk = [ 'phy:/dev/hdX,hda1,w', 'phy:/dev/hdY,hda2,w' ]

        If we use a single file
        -----------------------
        disk = [ 'file:/stroje/stroj.img,hda1,w' ]

        If we use several files
        -----------------------
        disk = [ 'file:/stroje/stroj.img,hda1,w', 'file:/stroje/stroj_usr.img,hda2,w' ]

X. Linkz

asciiart

        http://www1.shorewall.net/XenMyWay.html
        http://www1.shorewall.net/XenMyWay-Routed.html

        XEN on DEBIAN domU
        ------------------
        http://wiki.xensource.com/xenwiki/DebianDomU
        http://www.jejik.com/articles/2007/03/a_test_drive_of_debian_etch_xen/
        http://blackhole.sk/topicxen-ha-cluster-installation

        LVM XEN
        -------
        http://wiki.rpath.com/wiki/Xen_DomU_Guide

        preparing LVM for dom0
        ----------------------
        http://wiki.rpath.com/wiki/Virtual_Appliances:Essential_Logical_Volume_Management_for_Xen_DomU_Deployment

        http://julien.danjou.info/xen.html

Current practice (checked 2026-10)

noteThe article above is kept as it was written in 2008. This section lists what has changed since and what to do instead today.

xm commands: xm was removed in Xen 4.5. The same steps with xl are below; note that xl shutdown has no -H option (use -w to wait for the guest to go down).

bash

$ # xl create -c /etc/xen/www.vhosts.example.cfg
$ # xl console www.vhosts.example
$ # xl shutdown -w www.vhosts.example
$ # xl destroy www.vhosts.example

xen-tools: xen-create-image comes from the xen-tools package, which is in Debian unstable but was removed from testing in February 2025 and is not in the current stable release. dist = etch installs a release that has been end-of-life since 2010-02-15.
Guest kernel: kernel = and initrd = point at the dom0's own kernel in /boot, so every guest runs the dom0 kernel and cannot update it by itself. Today the guest config can load GRUB instead (package grub-xen, for example kernel = "/usr/lib/grub-xen/grub-i386-xen_pvh.bin" for a PVH guest) and the guest boots the kernel installed inside its own filesystem. The older pygrub is deprecated.
Guest type: these are PV guests. Add type = "pvh" for a current Linux guest; memory and vcpus are plain numbers in an xl config, and embedded Python is not supported.
Network scripts: (network-script ...) and (vif-script ...) in xend-config.sxp no longer exist. The hotplug script is chosen per interface with script= in the vif line (default vif-bridge, bridge xenbr0); routing, forwarding and NAT in dom0 are yours to set up.
iptables and route: the NAT rules still load through the iptables-nft compatibility layer, but nftables is the default framework in Debian since Debian 10 and new rule sets are written for nft. route add 10.62.2.45 gw 10.62.2.44 is ip route add 10.62.2.45 via 10.62.2.44 with iproute2.
Disk lines: the phy: and file: prefixes are stripped and ignored by xl, and for Linux PV guests only xvd* device names are recommended, because the hda1/sda1 names stop working with recent guest kernels. A current line looks like this:

ini

disk = [ '/dev/system/www.vhosts.example-disk,raw,xvda1,rw' ]

Sources: