Chapter 20. Sharing files between the host and its virtual machines

Procedure

1. For each directory on the host that you want to share with your VM, set it as a virtiofs file system in the VM’s XML configuration.

   1. Open the XML configuration of the intended VM.

      # virsh edit vm-name

   2. Add an entry similar to the following to the <devices> section of the VM’s XML configuration.

      <filesystem type='mount' accessmode='passthrough'>
        <driver type='virtiofs'/>
        <binary path='/usr/libexec/virtiofsd' xattr='on'/>
        <source dir='/root/shared-files'/>
        <target dir='host-file-share'/>
      </filesystem>

      This example sets the /root/shared-files directory on the host to be visible as host-file-share to the VM.

2. Set up shared memory for the VM. To do so, add shared memory backing to the <domain> section of the XML configuration:

   <domain>
    [...]
    <memoryBacking>
      <access mode='shared'/>
    </memoryBacking>
    [...]
   </domain>

3. Boot up the VM.

   # virsh start vm-name

4. On your Windows VM, install WinFsp. To do so, mount the virtio-win ISO image, start the winfsp MSI installer, and follow the prompts.

   In the Custom Setup window of the installation wizard, select the features you want to install on the VM.

5. Start the virtiofs service:

   # sc start VirtioFsSvc

6. Navigate to This PC:

   File Explorer This PC

   If configured correctly, virtiofs is available on the Windows VM as the first available drive letter starting with Z: and going backwards. For example, my_viofs (Z:).

   Important

   You must restart the virtiofs service after each VM reboot to access the shared directory.

7. Optional: To set up additional virtiofs instances:

   1. Stop the virtiofs service:

      # sc stop VirtioFsSvc
      # sc config VirtioFsSvc start=demand

   2. Configure the WinFSP.Launcher service to set up multiple virtiofs instances:

      # "C:\Program Files (x86)\WinFsp\bin\fsreg.bat" virtiofs "<path to the binary>\virtiofs.exe" "-t %1 -m %2"

   3. Mount virtiofs instances to drives.

      For example, to mount virtiofs with the tag mount_tag0 to the Y: drive:

      "C:\Program Files (x86)\WinFsp\bin\launchctl-x64.exe" start virtiofs viofsY mount_tag0 Y:

   4. Repeat the previous step to mount all of your virtiofs instances.

   5. To unmount the virtiofs instance:

      "C:\Program Files (x86)\WinFsp\bin\launchctl-x64.exe" stop virtiofs viofsY

Verification

1. On your Windows VM, navigate to This PC:

   File Explorer This PC

   • If you did not specify a mount point when setting up the virtiofs service, it will use the first available drive letter starting with z: and going backwards.
   • If you have multiple virtiofs instances set up, they will appear as drives with the letters you had assigned to the instances.