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. Add a NUMA topology for shared memory to the XML configuration. The following example adds a basic topology for all CPUs and all RAM.

   <cpu mode='host-passthrough' check='none'>
     <numa>
       <cell id='0' cpus='0-{number-vcpus - 1}' memory='{ram-amount-KiB}' unit='KiB' memAccess='shared'/>
     </numa>
   </cpu>

3. Add shared memory backing to the <domain> section of the XML configuration:

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

4. Boot up the VM.

   # virsh start vm-name

5. Mount the file system in the guest operating system. The following example mounts the previously configured host-file-share directory with a Linux guest operating system.

   # mount -t virtiofs host-file-share /mnt

Procedure

1. 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.

2. Start the virtiofs service:

   # sc start VirtioFsSvc

3. Navigate to This PC:

   File Explorer → This PC

   Virtiofs should be 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.

4. 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.

Procedure

1. In the Virtual Machines interface, click the VM with which you want to share files.

   A new page opens with an Overview section with basic information about the selected VM and a Console section.

2. Scroll to Shared directories.

   The Shared directories section displays information about the host files and directories shared with that VM and options to Add or Remove a shared directory.

   

3. Click Add shared directory.

   The Share a host directory with the guest dialog appears.

   

4. Enter the following information:

   • Source path - The path to the host directory that you want to share.
   • Mount tag - The tag that the VM uses to mount the directory.

5. Set additional options:

   • Extended attributes - Set whether to enable extended attributes, xattr, on the shared files and directories.

6. Click Share.

   The selected directory is shared with the VM.

Procedure

1. In the Virtual Machines interface, click on the VM from which you want to remove the shared files.

   A new page opens with an Overview section with basic information about the selected VM and a Console section.

2. Scroll to Shared directories.

   The Shared directories section displays information about the host files and directories shared with that VM and options to Add or Remove a shared directory.

   

3. Click Remove next to the directory that you want to unshare with the VM.

   The Remove filesystem dialog appears.

   

4. Click Remove.

   The selected directory is unshared with the VM.