How to do it...

The following steps outline the process of inspecting and editing the XML definition of a KVM instance:

1. Ensure that you have a running KVM instance with libvirt, if not, follow the steps in the previous recipe:

root@kvm:~# virsh list
 Id Name State
----------------------------------------------------
 11 kvm1 running

root@kvm:~#

1. Dump the instance configuration file to standard output (stdout). For more information on stdout refer to folllowing link:

https://en.wikipedia.org/wiki/Standard_streams

root@kvm:~# virsh dumpxml kvm1
<domain type='kvm' id='11'>
 <name>kvm1</name>
 <uuid>9eb9a2e9-abb2-54c5-5cb3-dc86728e70fc</uuid>
 <memory unit='KiB'>1048576</memory>
 <currentMemory unit='KiB'>1048576</currentMemory>
 <vcpu placement='static'>1</vcpu>
 <resource>
   <partition>/machine</partition>
 </resource>
 <os>
   <type arch='x86_64' machine='pc-i440fx-trusty'>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/bin/qemu-system-x86_64</emulator>
   <disk type='file' device='disk'>
     <driver name='qemu' type='raw'/>
     <source file='/tmp/debian.img'/>
     <target dev='hda' bus='ide'/>
     <alias name='ide0-0-0'/>
     <address type='drive' controller='0' bus='0' target='0' unit='0'/>
   </disk>
   <controller type='usb' index='0'>
     <alias name='usb0'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
   </controller>
   <controller type='pci' index='0' model='pci-root'>
     <alias name='pci.0'/>
   </controller>
   <controller type='ide' index='0'>
     <alias name='ide0'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
   </controller>
   <interface type='network'>
     <mac address='52:54:00:d1:70:df'/>
     <source network='default'/>
     <target dev='vnet0'/>
     <model type='rtl8139'/>
    <alias name='net0'/>
    <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
   </interface>
   <serial type='pty'>
     <source path='/dev/pts/0'/>
     <target port='0'/>
     <alias name='serial0'/>
   </serial>
   <console type='pty' tty='/dev/pts/0'>
     <source path='/dev/pts/0'/>
     <target type='serial' port='0'/>
     <alias name='serial0'/>
   </console>
   <input type='mouse' bus='ps2'/>
   <input type='keyboard' bus='ps2'/>
   <graphics type='vnc' port='5900' autoport='yes' listen='146.20.141.158'>
     <listen type='address' address='146.20.141.158'/>
   </graphics>
   <video>
     <model type='cirrus' vram='9216' heads='1'/>
     <alias name='video0'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
   </video>
   <memballoon model='virtio'>
     <alias name='balloon0'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
   </memballoon>
 </devices>
 <seclabel type='none'/>
</domain>

root@kvm:~#

1. Save the configuration to a new file, as follows:

root@kvm:~# virsh dumpxml kvm1 > kvm1.xml
root@kvm:~# head kvm1.xml
<domain type='kvm' id='11'>
 <name>kvm1</name>
 <uuid>9eb9a2e9-abb2-54c5-5cb3-dc86728e70fc</uuid>
 <memory unit='KiB'>1048576</memory>
 <currentMemory unit='KiB'>1048576</currentMemory>
 <vcpu placement='static'>1</vcpu>
 <resource>
   <partition>/machine</partition>
 </resource>
 <os>
root@kvm:~#

1. Edit the configuration in place and change the available memory for the VM:

root@kvm:~# virsh edit kvm1
Domain kvm1 XML configuration edited.

root@kvm:~#