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Install Xen on CentOS

Xen is an Open Source Virtualization software developed by the Linux Foundation and is supported by Intel. Amazon AWS use Xen for powering its EC2 instances. Other alternative for Xen are KVM, OpenVZ, WMWare and LXC.

To install Xen on CentOS, run

yum install -y centos-release-xen
yum update
yum install -y xen

Now reboot the server, so server will boot with Xen kernal.

Verify Xen is running with command

xl info
[root@xen01 ~]# xl info
host                   : xen01.hostonnet.com
release                : 4.9.13-22.el6.x86_64
version                : #1 SMP Sun Feb 26 22:18:35 UTC 2017
machine                : x86_64
nr_cpus                : 8
max_cpu_id             : 11
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 2
cpu_mhz                : 2666
hw_caps                : bfebfbff:28000800:00000000:00003b00:0098e3bd:00000000:00000001:00000000
virt_caps              : hvm
total_memory           : 8190
free_memory            : 7072
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 6
xen_extra              : .3-8.el6
xen_version            : 4.6.3-8.el6
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Wed Feb 15 02:12:22 2017 -0600 git:35503e1-dirty
xen_commandline        : dom0_mem=1024M,max:1024M cpuinfo com1=115200,8n1 console=com1,tty loglvl=all guest_loglvl=all
cc_compiler            : gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-17)
cc_compile_by          : mockbuild
cc_compile_domain      : centos.org
cc_compile_date        : Tue Feb 28 14:18:26 UTC 2017
xend_config_format     : 4
[root@xen01 ~]# 

Setting up Bridge Networking

For setting up bridge networking, see instruction for your OS. CentOS 6, CentOS 7

Xen tunning

Edit /etc/xen/xend-config.sxp, set dom0 memory to 512 mb and disable balooning to avoid domU use up dom0’s memory.

vi /etc/xen/xend-config.sxp

Set following values

(dom0-min-mem 512)
(enable-dom0-ballooning no)

Disable Virtual Machines LVM volume showing up in boot menmu

Edit /etc/default/grub

vi /etc/default/grub

Add

GRUB_CMDLINE_XEN="dom0_mem=512M"
GRUB_DISABLE_OS_PROBER=true

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