2019-03-30 02:40:11 +00:00
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title = "Platforms (KVM)"
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weight = 30
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This document will help you set up your system to use a different gVisor
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platform.
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## What is a Platform?
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2019-04-02 21:27:54 +00:00
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gVisor requires a *platform* to implement interception of syscalls, basic
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context switching, and memory mapping functionality. These are described in
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more depth in the [Architecture Guide](../../architecture_guide/).
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2019-03-30 02:40:11 +00:00
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## Selecting a Platform
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The platform is selected by a `--platform` command line flag passed to `runsc`.
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To select a different platform, modify your Docker configuration
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(`/etc/docker/daemon.json`) to pass this argument:
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```json
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{
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"runtimes": {
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"runsc": {
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"path": "/usr/local/bin/runsc",
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"runtimeArgs": [
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"--platform=kvm"
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]
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}
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}
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}
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```
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Then restart the Docker daemon.
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## Example: Using the KVM Platform
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The KVM platform is currently experimental; however, it provides several
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benefits over the default ptrace platform.
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### Prerequisites
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You will also to have KVM installed on your system. If you are running a Debian
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based system like Debian or Ubuntu you can usually do this by installing the
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`qemu-kvm` package.
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```bash
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sudo apt-get install qemu-kvm
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```
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If you are using a virtual machine you will need to make sure that nested
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virtualization is configured. Here are links to documents on how to set up
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nested virtualization in several popular environments.
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* Google Cloud: [Enabling Nested Virtualization for VM Instances][nested-gcp]
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* Microsoft Azure: [How to enable nested virtualization in an Azure VM][nested-azure]
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* VirtualBox: [Nested Virtualization][nested-virtualbox]
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* KVM: [Nested Guests][nested-kvm]
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### Configuring Docker
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Per above, you will need to configure Docker to use `runsc` with the KVM
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platform. You will remember from the Docker Quick Start that you configured
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Docker to use `runsc` as the runtime. Docker allows you to add multiple
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runtimes to the Docker configuration.
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Add a new entry for the KVM platform entry to your Docker configuration
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(`/etc/docker/daemon.json`) in order to provide the `--platform=kvm` runtime
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argument.
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In the end, the file should look something like:
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```json
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{
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"runtimes": {
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"runsc": {
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"path": "/usr/local/bin/runsc"
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},
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"runsc-kvm": {
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"path": "/usr/local/bin/runsc",
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"runtimeArgs": [
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"--platform=kvm"
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]
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}
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}
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}
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```
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You must restart the Docker daemon after making changes to this file, typically
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this is done via `systemd`:
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```bash
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sudo systemctl restart docker
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```
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## Running a container
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Now run your container using the `runsc-kvm` runtime. This will run the
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container using the KVM platform:
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```bash
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docker run --runtime=runsc-kvm hello-world
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```
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[nested-azure]: https://docs.microsoft.com/en-us/azure/virtual-machines/windows/nested-virtualization
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[nested-gcp]: https://cloud.google.com/compute/docs/instances/enable-nested-virtualization-vm-instances
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[nested-virtualbox]: https://www.virtualbox.org/manual/UserManual.html#nested-virt
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[nested-kvm]: https://www.linux-kvm.org/page/Nested_Guests
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