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kata-deploy: QEMU, for 2.x, already includes virtiofs
There's no reason to ship qemu & qemu-virtiofs when the former already includes vitiofs support (and that's the default for 2.x deployments). In case we will enable experimental qemu DAX support, we should add a new target, a "qemu-experimental" target, as Carlos has been working on. Fixes: #1424 Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
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Fabiano Fidêncio
@@ -1,61 +1,12 @@
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# Kata Containers with virtio-fs
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- [Introduction](#introduction)
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- [Pre-requisites](#pre-requisites)
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- [Install Kata Containers with virtio-fs support](#install-kata-containers-with-virtio-fs-support)
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- [Run a Kata Container utilizing virtio-fs](#run-a-kata-container-utilizing-virtio-fs)
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- [Kata Containers with virtio-fs](#kata-containers-with-virtio-fs)
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- [Introduction](#introduction)
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## Introduction
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Container deployments utilize explicit or implicit file sharing between host filesystem and containers. From a trust perspective, avoiding a shared file-system between the trusted host and untrusted container is recommended. This is not always feasible. In Kata Containers, block-based volumes are preferred as they allow usage of either device pass through or `virtio-blk` for access within the virtual machine.
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As of the 1.7 release of Kata Containers, [9pfs](https://www.kernel.org/doc/Documentation/filesystems/9p.txt) is the default filesystem sharing mechanism. While this does allow for workload compatibility, it does so with degraded performance and potential for POSIX compliance limitations.
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As of the 2.0 release of Kata Containers, [virtio-fs](https://virtio-fs.gitlab.io/) is the default filesystem sharing mechanism.
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To help address these limitations, [virtio-fs](https://virtio-fs.gitlab.io/) has been developed. virtio-fs is a shared file system that lets virtual machines access a directory tree on the host. In Kata Containers, virtio-fs can be used to share container volumes, secrets, config-maps, configuration files (hostname, hosts, `resolv.conf`) and the container rootfs on the host with the guest. virtio-fs provides significant performance and POSIX compliance improvements compared to 9pfs.
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Enabling of virtio-fs requires changes in the guest kernel as well as the VMM. For Kata Containers, experimental virtio-fs support is enabled through `qemu` and `cloud-hypervisor` VMMs.
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**Note: virtio-fs support is experimental in the 1.7 release of Kata Containers. Work is underway to improve stability, performance and upstream integration. This is available for early preview - use at your own risk**
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This document describes how to get Kata Containers to work with virtio-fs.
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## Pre-requisites
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Before Kata 1.8 this feature required the host to have hugepages support enabled. Enable this with the `sysctl vm.nr_hugepages=1024` command on the host.In later versions of Kata, virtio-fs leverages `/dev/shm` as the shared memory backend. The default size of `/dev/shm` on a system is typically half of the total system memory. This can pose a physical limit to the maximum number of pods that can be launched with virtio-fs. This can be overcome by increasing the size of `/dev/shm` as shown below:
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```bash
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$ mount -o remount,size=${desired_shm_size} /dev/shm
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```
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## Install Kata Containers with virtio-fs support
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The Kata Containers `qemu` configuration with virtio-fs and the `virtiofs` daemon are available in the [Kata Container release](https://github.com/kata-containers/runtime/releases) artifacts starting with the 1.9 release. Installation is available through [distribution packages](https://github.com/kata-containers/documentation/blob/master/install/README.md#supported-distributions) as well through [`kata-deploy`](https://github.com/kata-containers/packaging/tree/master/kata-deploy).
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**Note: Support for virtio-fs was first introduced in `NEMU` hypervisor in Kata 1.8 release. This hypervisor has been deprecated.**
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Install the latest release of Kata with `kata-deploy` as follows:
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```
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docker run --runtime=runc -v /opt/kata:/opt/kata -v /var/run/dbus:/var/run/dbus -v /run/systemd:/run/systemd -v /etc/docker:/etc/docker -it katadocker/kata-deploy kata-deploy-docker install
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```
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This will place the Kata release artifacts in `/opt/kata`, and update Docker's configuration to include a runtime target, `kata-qemu-virtiofs`. Learn more about `kata-deploy` and how to use `kata-deploy` in Kubernetes [here](https://github.com/kata-containers/packaging/tree/master/kata-deploy#kubernetes-quick-start).
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## Run a Kata Container utilizing virtio-fs
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Once installed, start a new container, utilizing `qemu` + `virtiofs`:
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```bash
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$ docker run --runtime=kata-qemu-virtiofs -it busybox
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```
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Verify the new container is running with the `qemu` hypervisor as well as using `virtiofsd`. To do this look for the hypervisor path and the `virtiofs` daemon process on the host:
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```bash
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$ ps -aux | grep virtiofs
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root ... /home/foo/build-x86_64_virt/x86_64_virt-softmmu/qemu-system-x86_64_virt
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... -machine virt,accel=kvm,kernel_irqchip,nvdimm ...
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root ... /home/foo/build-x86_64_virt/virtiofsd-x86_64 ...
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```
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You can also try out virtio-fs using `cloud-hypervisor` VMM:
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```bash
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$ docker run --runtime=kata-clh -it busybox
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```
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virtio-fs support works out of the box for `cloud-hypervisor` and `qemu`, when Kata Containers is deployed using `kata-deploy`. Learn more about `kata-deploy` and how to use `kata-deploy` in Kubernetes [here](https://github.com/kata-containers/packaging/tree/master/kata-deploy#kubernetes-quick-start).
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