how to install a CentOS 6.0 KVM guest on a CentOS 6.0 host server with virt-install and PXE

Question

The host server (running CentOS 6.0) only has one public IP address and will be hosting many KVM guests so it needs to use a virtual network switch configuration in NAT mode.

I have previously used pxelinux for automated installation of physical machines and would like to continue to use pxelinux for installation of KVM-guests. The reason for this is that I already have written some scripts that generate pxelinux configuration files and I would like to reuse them.

Could someone provide a step-by-step instruction of how to install a CentOS 6.0 KVM guest on a CentOS 6.0 host server?

I would like to use the command line as much as possible so I prefer virt-install to virt-manager.

The host server has only one LVM volume group: vg0

[root@server ~]# vgs
  VG   #PV #LV #SN Attr   VSize VFree 
  vg0    1   3   0 wz--n- 8.18t 97.90g

Answer 1

First install some requirements. (This might be more than actually needed)

yum -y groupinstall "X Window System"
yum -y groupinstall "Virtualization Client" 
yum -y groupinstall "Virtualization" 
yum -y groupinstall "Virtualization Platform" 
yum -y groupinstall "Virtualization Tools"
yum -y groupinstall "Desktop"
yum -y install xorg-x11-fonts-100dpi
yum -y install xorg-x11-fonts-75dpi
yum -y install xorg-x11-fonts-Type1 xorg-x11-font-utils
yum -y install man
yum -y install emacs

As stated in the question we already have an LVM volume group

[root@server ~]# vgs
  VG   #PV #LV #SN Attr   VSize VFree 
  vg0    1   3   0 wz--n- 8.18t 97.90g

First we create and define a libvirt storage pool from that LVM volume group

[root@server ~]# cat /tmp/foobar
<pool type='logical'>
  <name>pool0</name>
  <target>
    <path>/dev/vg0</path>
  </target>
</pool>
[root@server ~]# virsh pool-define /tmp/foobar
Pool pool0 defined from /tmp/foobar

[root@server ~]# virsh pool-start pool0
Pool pool0 started

[root@server ~]# virsh pool-autostart pool0
Pool pool0 marked as autostarted

[root@server ~]# virsh pool-list
Name                 State      Autostart 
-----------------------------------------
pool0                  active     yes       

Per default libvirt already has a virtual network configured. It is named default. In this example we will redefine that virtual network so that we can use it for PXE install.

[root@server ~]# virsh net-list
Name                 State      Autostart
-----------------------------------------
default              active     yes       

[root@server ~]# emacs /tmp/default.xml
[root@server ~]# cat /tmp/default.xml
<network>
  <name>default</name>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0' />
  <ip address='10.0.0.1' netmask='255.255.0.0'>
    <tftp root='/var/lib/dnsmasq/tftpboot' />
    <dhcp>
      <range start='10.0.0.2' end='10.0.255.255' />
      <host mac='02:54:00:13:be:e4' name='virt1.example.com' ip='10.0.0.2' />
      <host mac='02:52:2c:a3:11:42' name='virt2.example.com' ip='10.0.0.3' />
      <bootp file='/pxelinux.0' />
    </dhcp>
  </ip>
</network>

The MAC addresses, 02:54:00:13:be:e4 and 02:52:2c:a3:11:42 seen above are just some random MAC addresses. (see the serverfault question: how to generate a random MAC address from the Linux command line)

[root@server ~]# virsh net-destroy default
Network default destroyed

[root@server ~]# virsh net-undefine default
Network default has been undefined

[root@server ~]# virsh net-define /tmp/default.xml
Network default defined from /tmp/default.xml

[root@server ~]# virsh net-start default
Network default started

[root@server ~]# virsh net-autostart default
Network default marked as autostarted

[root@server ~]# mkdir /var/lib/dnsmasq/tftpboot      
[root@server ~]# ls -lZd /var/lib/dnsmasq/tftpboot
drwxr-xr-x. root root unconfined_u:object_r:dnsmasq_lease_t:s0 /var/lib/dnsmasq/tftpboot
[root@server ~]# yum install syslinux
[root@server ~]# rpm -ql syslinux | grep pxelinux.0
/usr/share/syslinux/gpxelinux.0
/usr/share/syslinux/pxelinux.0
[root@server ~]# cp /usr/share/syslinux/pxelinux.0 /var/lib/dnsmasq/tftpboot/
[root@server ~]# cd /var/lib/dnsmasq/tftpboot/
[root@server tftpboot]# wget -O centos-6-vmlinuz.x86_64 http://ftp.funet.fi/pub/Linux/mirrors/centos/6.0/os/x86_64/images/pxeboot/vmlinuz
[root@server tftpboot]# wget -O centos-6-initrd.img.x86_64 http://ftp.funet.fi/pub/Linux/mirrors/centos/6.0/os/x86_64/images/pxeboot/initrd.img
[root@server tftpboot]# mkdir /var/lib/dnsmasq/tftpboot/pxelinux.cfg
[root@server tftpboot]# cd /var/lib/dnsmasq/tftpboot/pxelinux.cfg

The MAC address 02:54:00:13:be:e4 used above needs the configuration filename 01-02-54-00-13-be-e4. In other words prepend 01- and convert : into -.

[root@server pxelinux.cfg]# emacs 01-02-54-00-13-be-e4
[root@server pxelinux.cfg]# cat 01-02-54-00-13-be-e4
default local
prompt 1
timeout 50

label local
  localboot 0

label install
  kernel /centos-6-vmlinuz.x86_64
  append initrd=/centos-6-initrd.img.x86_64 ks=http://www.example.com/kickstart-files/virt1.example.com.txt device=eth0 ramdisk_size=9216 lang= devfs=nomount  

[root@server pxelinux.cfg]# cd

Here we assumed that the kickstart file for virt1.example.com can be downloaded from http://www.example.com/kickstart-files/virt1.example.com.txt

Now we run service libvirtd reload. This seems to be required for the dnsmasq tftpserver to run properly.

[root@server ~]# service libvirtd reload
Reloading libvirtd configuration:                          [  OK  ]

Now run virt-install to create the KVM guest virt1.example.com with 20 Gb disk space.

[root@server ~]# virt-install --debug --hvm --vnc --name virt1.example.com --os-type=linux --os-variant=rhel6 --pxe --network network=default,model=e1000,mac=02:54:00:13:be:e4 --disk pool=pool0,size=20 --ram 1024 --vcpus=1 

Now the graphical program virt-viewer will pop up an X-window. When you see "boot: " during the boot sequence, type install.

A note about the virt-install command line options: Using model=virtio didn't work for me, but luckily model=e1000 worked just fine.