wiki/gofurther/virtiofs.md

title	description	published	date	tags	editor	dateCreated
Share a host directory with a guest using virtiofs		true	2023-01-24T16:49:37.566Z		markdown	2022-08-13T00:16:17.437Z

Sharing a directory

As of January 2023, virtio-fs is only available for virtual machines managed by the system libvirt instance (qemu:///system) {.is-info}

As of January 2023, virtio-fs does not feature a read-only mode. Do not share a host directory with an untrusted guest. {.is-warning}

Virtio-fs, shorts for virtio shared filesystem, allows you to share a directory located on the host with a guest.

It is designed to be fast and optimized for local usage, when the host and the guest are located on the same physical machine.

The guest

Edit XML configuration

• Memory backing needs to be added to the XML definition:

<domain type="kvm">
[...]
    <memoryBacking>
        <source type="memfb"/>
        <access mode="shared/>"
    </memoryBacking>
[...]
</domain>

• A filesystem device has to be added.

<domain type="kvm">
[...]
    <devices>
    [...]
        <filesystem type="mount" accessmode="passthrough">
            <driver type="virtiofs"/>
            <source dir="/mnt/"> # The host directory to be shared with the guest
            <target dir="share"/> # Contrary to what the name implies, this is the tag used inside the guest
        </filesystem>
    [...]
    </devices>
[...]
</domain>    

Mount the folder inside the guest

• Inside the guest VM, mount the folder using the following commmand to mount the /mnt host directory on the guest, using also the /mnt point:

# mount -t virtiofs share /mnt/

Resources

• Official website: https://virtio-fs.gitlab.io/index.html#status
• In the context of a Windows guest: https://github.com/virtio-win/kvm-guest-drivers-windows/wiki/VirtIO-FS:-Shared-file-system
• https://wiki.archlinux.org/title/Libvirt#Sharing_data_between_host_and_guest