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Option 1
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virt-install –connect qemu:///system –name centos62dfltnogui –ram=1024 –vcpus=1 –disk path=/ssd1vmimages/centos62dfltnogui.img,size=12 –network bridge:br0 –graphics none –location=/var/www/html/centos62i386/ –extra-args “ks=http://10.0.0.12/vm.ks console=ttyS0”

# Generates:
<domain type=’kvm’>
<name>centos62dfltnogui</name>
<uuid>8b2263db-960d-cf15-02f2-70823460878e</uuid>
<memory>1048576</memory>
<currentMemory>1048576</currentMemory>
<vcpu>1</vcpu>
<os>
<type arch=’x86_64′ machine=’rhel6.2.0′>hvm</type>
<boot dev=’hd’/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<clock offset=’utc’/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/libexec/qemu-kvm</emulator>
<disk type=’file’ device=’disk’>
<driver name=’qemu’ type=’raw’ cache=’none’/>
<source file=’/ssd1vmimages/centos62dfltnogui.img’/>
<target dev=’vda’ bus=’virtio’/>
<address type=’pci’ domain=’0x0000′ bus=’0x00′ slot=’0x04′ function=’0x0’/>
</disk>
<interface type=’bridge’>
<mac address=’52:54:00:98:e0:1e’/>
<source bridge=’br0’/>
<model type=’virtio’/>
<address type=’pci’ domain=’0x0000′ bus=’0x00′ slot=’0x03′ function=’0x0’/>
</interface>
<serial type=’pty’>
<target port=’0’/>
</serial>
<console type=’pty’>
<target type=’serial’ port=’0’/>
</console>
<input type=’tablet’ bus=’usb’/>
<memballoon model=’virtio’>
<address type=’pci’ domain=’0x0000′ bus=’0x00′ slot=’0x05′ function=’0x0’/>
</memballoon>
</devices>
</domain>

------------------------------
Option 2
------------------------------
virt-install \
    -n centos \
    -r 2048 \
    --vcpus=1 \
    --os-variant=rhel5.4 \
    --accelerate \
    -v \
    -w bridge:br0 \
    -w bridge:br1 \
    --disk path=/emc/kvm/centos.img,size=100 \
    -l http://mirrors.nixcraft.in/centos/5.5/os/x86_64/ \
    -nographics \
    -x "ks=http://10.10.21.3/static/ks.cfg ksdevice=eth0 ip=10.10.21.76 netmask=255.255.255.240 dns=10.10.21.1 gateway=10.10.21.100"

Matches kickstart file:

auth  --useshadow  --enablemd5
bootloader --location=mbr
zerombr
clearpart --all --initlabel
text
firewall --enabled --port=22:tcp
firstboot --disable
keyboard us
network --device eth0 --bootproto static --ip 10.10.21.76 --netmask 255.255.255.240 --gateway 10.10.21.100 --nameserver 10.10.21.1,10.10.21.2 --noipv6
network --device eth1 --bootproto static --ip 123.1.2.6 --netmask 255.255.255.240 --gateway 123.1.2.100 --nameserver 10.10.21.1,10.10.21.2 --hostname centos.nixcraft.in --noipv6
lang en_US
logging --level=info
url --url=http://mirrors.nixcraft.in/centos/5.5/os/x86_64/ 
reboot
rootpw --iscrypted $1$somepassword
selinux --enforcing
skipx
timezone  America/New_York
install
part / --bytes-per-inode=4096 --fstype="ext3" --grow --size=1
part swap --recommended
%packages
@core
--nobase
%post
(
 echo '10.0.0.0/8 via 10.10.21.100' > /etc/sysconfig/network-scripts/route-eth0
 sed -i 's/LABEL=\//& console=ttyS0/' /etc/grub.conf
 echo 'S0:12345:respawn:/sbin/agetty ttyS0 115200' >> /etc/inittab
 echo "ttyS0" >> /etc/securetty
 echo 'IPV6INIT=no' >> /etc/sysconfig/network
 echo 'install ipv6 /bin/true' >> /etc/modprobe.conf
 ) 1>/root/post_install.log 2>&1

------------------------------
Option 3
------------------------------
sudo virt-install -n virt64_01 -r 8192 \
       --disk path=/media/newhd/virt64_01.img,bus=virtio,size=50 \
       -c ubuntu-14.04.1-server-amd64.iso \
       --network bridge=br0,model=virtio,mac=52:54:00:b2:cb:b0 \
       --network bridge=br1,model=virtio \
       --video=vmvga --graphics vnc,listen=0.0.0.0 --noautoconsole -v --vcpus=4