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Docker in workspaces

Container-based virtual machines (CVMs) allow users to run system-level programs, such as Docker and systemd, in their workspaces.

If you're a site admin or a site manager, you can enable CVMs as a workspace deployment option.

Infrastructure requirements

You can use any cloud provider that supports the above requirements, but we have instructions on how to set up supported clusters on AWS and Google. Azure-hosted clusters will meet these requirements as long as you use Kubernetes version 1.18+.

HostPath mounts

The host paths required for CVM functionality depend on whether you've enabled Caching and Auto loading of the shiftfs kernel module. You can find these settings under Manage > Admin > Infrastructure.

The following table documents the host paths that are mounted:

CachingAuto Load shiftfs/usr/src/lib/modules/var/run/var/lib
OffN/ARead-onlyRead-only
OnOffRead-onlyRead-onlyRead-onlyRead-write
OnOnRead-writeRead-writeRead-onlyRead-write

Security

The container-based virtual machine deployment option leverages the Sysbox container runtime to offer a VM-like user experience while retaining the footprint of a typical container.

Coder first launches a supervising container with additional privileges. This container is standard and included with the Coder release package. During the workspace build process, the supervising container launches an inner container using the Sysbox container runtime. This inner container is the user’s workspace.

The user cannot gain access to the supervising container at any point. The isolation between the user's workspace container and its outer, supervising container is what provides strong isolation.

Sysbox is not yet supported on systems with SELinux enabled.

Known issues

  • Do not add configuration files like bash scripts to /tmp in CVMs since they will not be available once the CVM workspace is built. Consider creating another directory like /mycompanyname

  • Coder requires an older version of containerd.io because it contains a version of runc that works with Sysbox correctly. See our enterprise-base Dockerfile for an example or install the following in your Dockerfile containerd.io=1.5.11-1. In a future release, Coder will update to the latest Sysbox version that supports the latest runc.

  • NVIDIA GPUs can be added to CVMs on bare metal clusters only. This feature is not supported on Google Kubernetes Engine or other cloud providers at this time.

    Support for NVIDIA GPUs is in beta. We do not support AMD GPUs at this time.

Next Steps

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