86 lines
2.5 KiB
Markdown
86 lines
2.5 KiB
Markdown
---
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title: Share a host directory with a guest using virtiofs
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description:
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published: true
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date: 2023-02-02T19:13:08.447Z
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tags:
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editor: markdown
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dateCreated: 2022-08-13T00:16:17.437Z
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---
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# Sharing a directory
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> For KVM/QEMU, as of January 2023, virtio-fs is only available for virtual machines managed by the system libvirt instance (`qemu:///system`)
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{.is-warning}
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> As of January 2023, virtio-fs does not support read-only mode, meaning a guest will be able to write to the host's folder.
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{.is-warning}
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[Virtio-fs](https://virtio-fs.gitlab.io/), shorts for virtio shared filesystem, allows for a directory located on the host to be shared with a guest.
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It is designed to be fast and optimized for local usage, when the host and the guest are located on the same physical machine.
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Just as with other virtio devices, it requires specialized drivers to be written for the guest operating system.
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## The guest
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### Edit XML configuration
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* Memory backing needs to be added to the XML definition:
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```
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<domain type="kvm">
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[...]
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<memoryBacking>
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<source type="memfb"/>
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<access mode="shared/>"
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</memoryBacking>
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[...]
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</domain>
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```
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* Add the filesystem device to the guest. In this the following case, the directory `/opt/share/` will be shared with the guest:
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```
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<domain type="kvm">
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[...]
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<devices>
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[...]
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<filesystem type="mount" accessmode="passthrough">
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<driver type="virtiofs"/>
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<source dir="/opt/share"> # The host directory to be shared with the guest
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<target dir="share"> # The target dir value refers to the mount tag used inside the guest, not the target dir inside the guest
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</filesystem>
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[...]
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</devices>
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[...]
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</domain>
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```
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### Mount the folder inside the guest
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* Inside the guest VM, mount the folder using the following command to mount the `/opt/share` host directory to the guest, using also the `/mnt` point:
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`# mount -t virtiofs share /mnt/`
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* To make it permanent, edit `/etc/fstab` to look like the following:
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```
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share /mnt/ virtiofs rw,noatime,_netdev 0 0
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```
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* Make sure it works before rebooting the guest virtual machine, by un-mounting the share
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`# umount /mnt/`
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* and then mounting all share available in fstab:
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`# mount all`
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## Resources
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* Official website: https://virtio-fs.gitlab.io/index.html#status
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* In the context of a Windows guest: https://github.com/virtio-win/kvm-guest-drivers-windows/wiki/VirtIO-FS:-Shared-file-system
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* https://wiki.archlinux.org/title/Libvirt#Sharing_data_between_host_and_guest
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