Add documentation for configuring shim runtime options (#43)

docs/README.md

@@ -5,3 +5,4 @@ Everything you need to know about gvisor-containerd-shim
 - [Untrusted Workload Quick Start (containerd >=1.1)](untrusted-workload-quickstart.md)
 - [Runtime Handler Quick Start (containerd >=1.2)](runtime-handler-quickstart.md)
 - [Runtime Handler Quick Start (shim v2) (containerd >=1.2)](runtime-handler-shim-v2-quickstart.md)
+- [Configure containerd-shim-runsc-v1 (shim v2) (containerd >= 1.3)](configure-containerd-shim-runsc-v1.md)

docs/configure-containerd-shim-runsc-v1.md

@@ -0,0 +1,42 @@
+# Configure containerd-shim-runsc-v1 (Shim V2)
+
+This document describes how to configure runtime options for `containerd-shim-runsc-v1`.
+This is follows on to the instructions of [Runtime Handler Quick Start (shim v2) (containerd >=1.2)](runtime-handler-shim-v2-quickstart.md) and requires containerd 1.3 or later.
+
+## Configuration
+
+`containerd-shim-runsc-v1` supports a few different configuration options based on the version of containerd that is used. For versions >= 1.3, it supports a configurable config path in the containerd runtime configuration.
+
+1. Update `/etc/containerd/config.toml` to point to a configuration file for `containerd-shim-runsc-v1`.
+
+```shell
+{ # Step 1: Update runtime options for runsc in containerd config.toml
+cat <<EOF | sudo tee /etc/containerd/config.toml
+disabled_plugins = ["restart"]
+[plugins.linux]
+  shim_debug = true
+[plugins.cri.containerd.runtimes.runsc]
+  runtime_type = "io.containerd.runsc.v1"
+[plugins.cri.containerd.runtimes.runsc.options]
+  TypeUrl = "io.containerd.runsc.v1.options"
+  ConfigPath = "/etc/containerd/runsc.toml"
+EOF
+}
+```
+
+2. Configure `/etc/containerd/runsc.toml` with the desired options. The set of options that can be configured can be found in [options.go](../pkg/v2/options/options.go). This example shows how to configure `containerd-shim-runsc-v1` to use gvisor with the kvm platform.
+
+```shell
+{ # Step 2: Create containerd-shim-runsc-v1 runtime options config
+cat <<EOF | sudo tee /etc/containerd/runsc.toml
+[runsc_config]
+platform = "kvm"
+EOF
+}
+```
+
+3. Restart `containerd`
+
+```shell
+sudo systemctl restart containerd
+```