No more maintained.
Now just a test in a lab.
Xen
Xen virtualization
/etc/xen/xend.config
Tipo Infobox: PATH - Skill: 5- SENIOR
A sample xend.config file with live relocation and bridging on multiple interfaces activated.
#(logfile /var/log/xen/xend.log)
#(loglevel DEBUG)
(xend-http-server yes)
(xend-unix-server yes)
#(xend-tcp-xmlrpc-server no)
#(xend-unix-xmlrpc-server yes)
#(xend-relocation-server no)
(xend-unix-path /var/lib/xend/xend-socket)
(xend-port 8000)
# Options for enabling live-relocations (warn, no access limits defined)
(xend-relocation-port 8002)
(xend-address '')
#(xend-address localhost)
(xend-relocation-address '')(xend-relocation-hosts-allow '')
# Options for enabling bridging on multiple physical interfaces
#(xend-relocation-hosts-allow '^localhost$^localhost\\.localdomain$')
#(console-limit 1024)
# (network-script network-bridge)
# (network-script 'network-bridge netdev=eth1')
# (network-script 'network-bridge bridge=<name>')
(network-script network-bridge-custom)
(vif-script vif-bridge)
#(network-script network-route)
#(vif-script vif-route)
#(network-script network-nat)
#(vif-script vif-nat)
(dom0-min-mem 256)
(dom0-cpus 0)
#(enable-dump no)
#(external-migration-tool '')
#(vnc-listen '127.0.0.1')
(vncpasswd '')
The custom script /etc/xen/scripts/network-bridge-custom for bridging on multiple interfaces can be edited according to need, can be something like:
#!/bin/bash
dir=$(dirname "$0")
"$dir/network-bridge" "$@" vifnum=0
"$dir/network-bridge" "$@" vifnum=1
"$dir/network-bridge" "$@" vifnum=2
Xen VM installation via Kickstart
Tipo Infobox: TIPS - Skill: 5- SENIOR
A sample /etc/xen/vmhost template file that can be used for installation via kickstart and then, after few changes, as configuration file for the newly installed Virtual Machine.
# Template XEN config for kickstarting servers
# Use this for first install ( change: name , disk location , extra (ks file))
# It is serviced from puppet, so work on a copy
# QUICK REFERENCE
# 1- COPY this file to a new one with the name of the server (es: syslog.xen )
# 2- EDIT syslog.xen: Change name , disk location , extra (ks file)
# 3- INSTALL: xm create -c syslog.xen
# 4- ADAPT configuration file:
# - Comment Kickstart bootstrap parameters
# - Uncomment bootloader parameter
# - Change on_reboot option, from destroy to restart
# Kickstart bootstrap parameters
kernel = "/boot/vmlinuz-xen-install"
ramdisk = "/boot/initrd-xen-install"
extra = "text ks=http://10.100.1.51/ks/XXX.ks ksdevice=eth1"
# Activate bootloader option after first install
# bootloader="/usr/bin/pygrub"
# Xen machine configuration settings
name = "XXX"
memory = "2048"
disk = [ 'phy:/dev/san/XXX_xen,xvda,w' ]
vif = [ 'bridge=xenbr0', 'bridge=xenbr1' ]
vcpus=8
# on_reboot should be destroy on first install, and restart in normal use
on_reboot = 'destroy'
on_crash = 'destroy'
Using NTP with XEN
Tipo Infobox: TIPS - Skill: 5- SENIOR
In order to effectively use an NTP source on a Xen Virtual Machine the sysctl kernel parameter xen.independent_wallclock must be set to 1.
Local clock on a Xen Linux machine is by default in sync with the clock of the Physical Host (Dom0), in order to change it and use time syncronization services as NTP, a kernel parameter must be set on the virtual machine:
echo 1 > /proc/sys/xen/independent_wallclock
For a boot resilitent configuration in the /etc/sysctl.conf of the virtual host add:
# Set independent wall clock time
xen.independent_wallclock=1
Xen shell commands
Tipo Infobox: DESCRIPTION - Skill: 5- SENIOR
Some more or less commonly used shell commands for managing Xen Virtual Machines (VM, also called Domains). Tested on Xen 3.0, should work also in other versions.
Basic commands
Show the running Virtual Machines: xm list
Start a virtual machine (myhost): xm create myhost
Gracefully shutdown (soft-reset) a virtual machine: xm shutdown myhost
Forced power Off (hard-reset) of a virtual machine: xm destroy myhost
Reboot a VM : xm reboot myhost
Using the console
Start a virtual machine and attach immediately a console: xm create -c myhost
Attach to the console of a VM (sample ID=4 for myhost, as shown in xm list):
xm console myhost or xm console 4
To leave / detach from the xen console press CTRL+5
Resources management and usage
To alter the RAM assigned to a VM (sample 256 Mb): xm mem-set myhost 256
To alter the CPUs assigned to a VM (sample 2 CPUs or cores):
xm vcpu-set myhost 2
Shows resource utilization of the running hosts: xm top or xentop
Shows Virtual Machines uptimes: xm uptime
Saving and Restoring
Virtual Machines state can be saved on a file and later restored (sample destination file /var/tmp/myhost.save)
xm save myhost /var/tmp/myhost.save
Note that after this command the VM is no longer active: you can reboot from start it with xm create myhost or restore the saved machine state with xm restore /var/tmp/myhost.save
Note also that the save file ( /var/tmp/myhost.save ) is only the dump on the VM memory, for backups it's of no use if you copy it to another physical host without copying also the VM config file and the file/LVM/partition used for the disk) .
Block Devices management
It's is possible to add block devices (disks) to a running VM:
To add a local file ( /var/tmp/data.disk ) as /dev/xvdc to the myhost paravirtualized VM, in write mode:
xm block-attach myhost file://var/tmp/data.disk /dev/xvdc w
Mode can be: w (read/write), r (read only), w! (shared read/write, when the samer device is attached to two different VMs).
The above file can be created (here 4 Gb) with:
dd if=/dev/zero of=/var/tmp/data.disk bs=1024k count=4096
To add a local physical disk, partition or LVM (for example an USB stick):
xm block-attach myhost phy://dev/sda /dev/xvdc w
Note that I/O performances are much better when using physical devices or LVM instead of plain files as block devices for the VMs.
To list the currently attached block devices to a VM:
xm block-list myhost --long or xm block-list myhost
To detach a block device (51744 is the Vdev in xm block-list)
xm block-detach myhost 51744
Bridging management
On Linux the bridge utils can be used to show and manage bridging:
brctl show
brctl showmacs xenbr0
To manually create a new xen bridge interface and associate it a physical device.
brctl addbr xenbr2
brctl addif peth3