On libvirt default storage pool is created called default, default pool will defined to use use location /var/lib/libvirt/images for file based volumes.
when ever i create a kvm vm it will create a image in .qcow2 default disk storage for the newly created vm, in other words it is called as volume.
Each vm created will have a voulme, volumes can be created before hand and volume destination can be provided for the virt-install command line.
Lets check the storage pools on the system.
virsh pool-list Name State Autostart ------------------------------------------- cipher active yes default active yes store active yes
from the above we have three storage pools under which volumes or .qcow2 disk allocations can be done to facilitate for vm installation.
Getting more information on pools.
virsh pool-info default Name: default UUID: 5a67026a-5879-4294-9595-297d79ae8d23 State: running Persistent: yes Autostart: yes Capacity: 78.24 GiB Allocation: 42.74 GiB Available: 35.51 GiB virsh pool-info store Name: store UUID: f51da59f-59e5-45d7-9f13-138a067ddc49 State: running Persistent: yes Autostart: yes Capacity: 596.17 GiB Allocation: 50.00 GiB Available: 546.17 GiB
Checking the volumes under the storage pool default.
virsh vol-list default Name Path ------------------------------------------------------------------------------ centos-VAGRANTSLASH-7_vagrant_box_image_1802.01.img /var/lib/libvirt/images/centos-VAGRANTSLASH-7_vagrant_box_image_1802.01.img centosext.qcow2 /var/lib/libvirt/images/centosext.qcow2 centosext1.qcow2 /var/lib/libvirt/images/centosext1.qcow2 centosext2.qcow2 /var/lib/libvirt/images/centosext2.qcow2 centosext3.qcow2 /var/lib/libvirt/images/centosext3.qcow2 centosext4.qcow2 /var/lib/libvirt/images/centosext4.qcow2 centosext5.qcow2 /var/lib/libvirt/images/centosext5.qcow2 chef-repo_node1.img /var/lib/libvirt/images/chef-repo_node1.img chef-repo_node2.img /var/lib/libvirt/images/chef-repo_node2.img chef-repo_node3.img /var/lib/libvirt/images/chef-repo_node3.img chefnode1.qcow2 /var/lib/libvirt/images/chefnode1.qcow2 chefnode2.qcow2 /var/lib/libvirt/images/chefnode2.qcow2 chefnode3.qcow2 /var/lib/libvirt/images/chefnode3.qcow2 chefnode4.qcow2 /var/lib/libvirt/images/chefnode4.qcow2 cipher_default.img /var/lib/libvirt/images/cipher_default.img haproxy_ha.img /var/lib/libvirt/images/haproxy_ha.img haproxy_one.img /var/lib/libvirt/images/haproxy_one.img haproxy_two.img /var/lib/libvirt/images/haproxy_two.img
volumes can be in .qcow2 or .img format, img was older default for volumes creation.
.qcow2 has added benefits over .img format and preferred for openstack deployments.
Voulmes can be in .qcow2 , .img or it can be lvm or physical partiton itlself.
Checking the volume information for storage pool “store”
virsh vol-list store Name Path ------------------------------------------------------------------------------ linux1 /dev/store/linux1 linux2 /dev/store/linux2
Creating new volumes, which can be used for new vm’s as storge disk destinations.
for this we need create a xml file vol-create a volume.
Here is a volume xml file for /var/lib/libvirt/images/centosext.qcow2
virsh vol-dumpxml /var/lib/libvirt/images/centosext.qcow2
<volume type='file'>
<name>centosext.qcow2</name>
<key>/var/lib/libvirt/images/centosext.qcow2</key>
<source>
</source>
<capacity unit='bytes'>107374182400</capacity>
<allocation unit='bytes'>3099361280</allocation>
<physical unit='bytes'>107390828544</physical>
<target>
<path>/var/lib/libvirt/images/centosext.qcow2</path>
<format type='qcow2'/>
<permissions>
<mode>0600</mode>
<owner>0</owner>
<group>0</group>
<label>unconfined_u:object_r:virt_image_t:s0</label>
</permissions>
<timestamps>
<atime>1522580831.457883233</atime>
<mtime>1520994404.759347857</mtime>
<ctime>1521800537.813106612</ctime>
</timestamps>
<compat>1.1</compat>
<features>
<lazy_refcounts/>
</features>
</target>
</volume>
Lets dump the output to alpha.xml
virsh vol-dumpxml /var/lib/libvirt/images/centosext.qcow2 > alpha.xml
cat alpha.xml
<volume type='file'>
<name>centosext.qcow2</name>
<key>/var/lib/libvirt/images/centosext.qcow2</key>
<source>
</source>
<capacity unit='bytes'>107374182400</capacity>
<allocation unit='bytes'>3099361280</allocation>
<physical unit='bytes'>107390828544</physical>
<target>
<path>/var/lib/libvirt/images/centosext.qcow2</path>
<format type='qcow2'/>
<permissions>
<mode>0600</mode>
<owner>0</owner>
<group>0</group>
<label>unconfined_u:object_r:virt_image_t:s0</label>
</permissions>
<timestamps>
<atime>1522580831.457883233</atime>
<mtime>1520994404.759347857</mtime>
<ctime>1521800537.813106612</ctime>
</timestamps>
<compat>1.1</compat>
<features>
<lazy_refcounts/>
</features>
</target>
</volume>
Edit the new alpha.xml file and plug in the desirable voulme name and size.
cat alpha.xml
<volume type='file'>
<name>alpha.qcow2</name>
<key>/var/lib/libvirt/images/alpha.qcow2</key>
<source>
</source>
<capacity unit='bytes'>107374182400</capacity>
<allocation unit='bytes'>3099361280</allocation>
<physical unit='bytes'>107390828544</physical>
<target>
<path>/var/lib/libvirt/images/alpha.qcow2</path>
<format type='qcow2'/>
<permissions>
<mode>0600</mode>
<owner>0</owner>
<group>0</group>
<label>unconfined_u:object_r:virt_image_t:s0</label>
</permissions>
<timestamps>
<atime>1522580831.457883233</atime>
<mtime>1520994404.759347857</mtime>
<ctime>1521800537.813106612</ctime>
</timestamps>
<compat>1.1</compat>
<features>
<lazy_refcounts/>
</features>
</target>
</volume>
Creating a voulme
$ $virsh vol-create default alpha.xml Vol alpha.qcow2 created from alpha.xml $virsh vol-list default Name Path ------------------------------------------------------------------------------ alpha.qcow2 /var/lib/libvirt/imaes/alpha.qcow2
Checking the size of newly created volume /var/lib/libvirt/images/alpha.qcow2
$ virsh vol-info /var/lib/libvirt/images/alpha.qcow2 Name: alpha.qcow2 Type: file Capacity: 100.00 GiB Allocation: 196.00 KiB
.qcow2, .img are file based volumes for kvm.
It may be difficult to get a xml file if the server is setup a new , does not have any vms setup on it yet ,in that case we can use vol-create-as to create a volume.
$ virsh vol-create-as default beta.qcow2 2G Vol beta.qcow2 created
Getting more info on the volumes.
$ virsh vol-list default Name Path ------------------------------------------------------------------------------ alpha.qcow2 /var/lib/libvirt/images/alpha.qcow2 beta.qcow2 /var/lib/libvirt/images/beta.qcow2
Identifying the the type of storege device and disk allocation size.
$ virsh vol-info /var/lib/libvirt/images/beta.qcow2 Name: beta.qcow2 Type: file Capacity: 2.00 GiB Allocation: 2.00 GiB
Data on the volumes can be wiped off , be reused to setup new vms on kvm node.
$ $virsh vol-wipe /var/lib/libvirt/images/alpha.qcow2 Vol /var/lib/libvirt/images/alpha.qcow2 wiped
Volumes can be deleted with vol-delete command.
$virsh vol-delete /var/lib/libvirt/images/alpha.qcow2 Vol /var/lib/libvirt/images/alpha.qcow2 deleted $virsh vol-delete /var/lib/libvirt/images/beta.qcow2 Vol /var/lib/libvirt/images/beta.qcow2 deleted
Creating volumes on lvm storage pool will be similar.
$virsh vol-create-as store linux4 25G ; virsh store vol-create-as linux5 25G Vol linux4 created
Deleting the creadted volume
$virsh vol-delete /dev/store/linux4 Vol /dev/store/linux4 deleted