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Runtime Configuration

Drop-in Files

When kata-deploy installs Kata Containers, the base configuration files at /opt/kata/share/defaults/kata-containers should not be modified directly. Instead, use drop-in configuration files to customize settings. This approach ensures your customizations survive kata-deploy upgrades.

How Drop-in Files Work

The Kata runtime reads the base configuration file and then applies any .toml files found in the config.d/ directory alongside it. Files are processed in alphabetical order, with later files overriding earlier settings.

Base Configuration Files

The base configuration references for the Go runtime can be found here, and for the Rust runtime here.

What runtime implementation am I using?

By looking at the /opt/kata/containerd/config.d/kata-deploy.toml file, each runtimeClass (ex. kata-qemu-nvidia-gpu, kata-qemu-nvidia-gpu-runtime-rs) is configured with a specific runtime_path. If this path is set to runtime_path = "/opt/kata/bin/containerd-shim-kata-v2" you are using the Go runtime. Otherwise if it's runtime_path = "/opt/kata/runtime-rs/bin/containerd-shim-kata-v2", it's the Rust runtime.

Note that Rust will be the default runtime in Kata v4.

Creating Custom Drop-in Files

The recommended way to create custom drop-in files is to use the helm chart. Drop-in files may also be added directly to the filesystem.

To add custom settings, create a .toml file in the appropriate config.d/ directory. Use a numeric prefix to control the order of application.

Reserved prefixes (used by kata-deploy):

  • 10-*: Core kata-deploy settings
  • 20-*: Debug settings
  • 30-*: Kernel parameters
  • 50-*: Settings from the helm chart

Recommended prefixes for custom settings: 50-89

Drop-In Config Examples

Adding Custom Kernel Parameters

Bash
# SSH into the node or use kubectl exec
sudo mkdir -p /opt/kata/share/defaults/kata-containers/runtimes/qemu/config.d/
sudo cat > /opt/kata/share/defaults/kata-containers/runtimes/qemu/config.d/50-custom.toml << 'EOF'
[hypervisor.qemu]
kernel_params = "my_param=value"
EOF

Changing Default Memory Size

Bash
sudo cat > /opt/kata/share/defaults/kata-containers/runtimes/qemu/config.d/50-memory.toml << 'EOF'
[hypervisor.qemu]
default_memory = 4096
EOF