KVM Virtualization Directory-Based Storage Pool Configuration
External
Internal
Overview
This procedure declares a local directory as a storage pool.
One case when this is useful is when we want to share DVD ISO images with the guest for installation as -disk=.../some-image.iso,device=cdrom argument for virt-install. If the image is not available in a storage pool, libvirt will automatically build a storage pool for it, and sometimes build multiple storage pools for the same image, which is something we want to avoid.
Procedure
Create the new directory, or us an existing directory.
mkdir /iso-images
Set directory ownership:
chown root:root /iso-images
Set directory permissions:
chmod 755 /iso-images
Configure SELinux file contexts. Note that the name of the pool and the directory do not have to match. However, a guest virtual machine is being shut down, libvirt has to set the context back to a default value. The context of the directory determines what this default value is. It is worth explicitly labeling the directory virt_image_t, so that when the guest virtual machine is shutdown, the images get labeled 'virt_image_t' and are thus isolated from other processes running on the host physical machine.
semanage fcontext -a -t virt_image_t '/iso-images(/.*)?'
restorecon -R /iso-images
Use virsh pool-define-as to define the new storage pool:
virsh pool-define-as iso-images dir --source-path /iso-images --target /iso-images
Start the storage pool:
virsh pool-start iso-images
Declare it "auto-start":
virsh pool-autostart iso-images
Storage Volume
Even if the ISO images are not declared as storage volumes, virt-install will create the corresponding storage volume if used during the guest installation.
Alternatively, they can be pre-staged as described in this procedure: