runtime: hard-code Firecracker API socket path

docs/getting-started.md

@@ -212,10 +212,6 @@ configuration file has the following fields:
   `firecracker` located in its working directory.  A fully-qualified path to the
   `firecracker` binary is recommended, as the working directory typically
   changes every execution when run by containerd.
-* `socket_path` (required) - A path where a socket file should be created for
-  communicating with the Firecracker API.  A relative path like
-  `./firecracker.sock` is recommended so that the socket is created in the
-  temporary working directory allocated by containerd.
 * `kernel_image_path` (required) - A path where the kernel image file is
   located.  A fully-qualified path is recommended.
 * `kernel_args` (required) - Arguments for the kernel command line.
@@ -241,7 +237,6 @@ configuration file has the following fields:
 ```json
 {
   "firecracker_binary_path": "/usr/local/bin/firecracker",
-  "socket_path": "./firecracker.sock",
   "kernel_image_path": "/var/lib/firecracker-containerd/runtime/hello-vmlinux.bin",
   "kernel_args": "console=ttyS0 noapic reboot=k panic=1 pci=off nomodules rw",
   "root_drive": "/var/lib/firecracker-containerd/runtime/hello-rootfs.ext4",

docs/quickstart.md

@@ -138,7 +138,6 @@ sudo mkdir -p /etc/containerd
 sudo tee -a /etc/containerd/firecracker-runtime.json <<EOF
 {
   "firecracker_binary_path": "/usr/local/bin/firecracker",
-  "socket_path": "./firecracker.sock",
   "kernel_image_path": "/var/lib/firecracker-containerd/runtime/hello-vmlinux.bin",
   "kernel_args": "console=ttyS0 noapic reboot=k panic=1 pci=off nomodules rw",
   "root_drive": "/var/lib/firecracker-containerd/runtime/hello-rootfs.ext4",

runtime/README.md

@@ -38,10 +38,6 @@ configuration file has the following fields:
   `firecracker` located in its working directory.  A fully-qualified path to the
   `firecracker` binary is recommended, as the working directory typically
   changes every execution when run by containerd.
-* `socket_path` (required) - A path where a socket file should be created for
-  communicating with the Firecracker API.  A relative path like
-  `./firecracker.sock` is recommended so that the socket is created in the
-  temporary working directory allocated by containerd.
 * `kernel_image_path` (required) - A path where the kernel image file is
   located.  A fully-qualified path is recommended.
 * `kernel_args` (required) - Arguments for the kernel command line.

runtime/config.go

@@ -24,12 +24,12 @@ import (
 const (
 	configPathEnvName = "FIRECRACKER_CONTAINERD_RUNTIME_CONFIG_PATH"
 	defaultConfigPath = "/etc/containerd/firecracker-runtime.json"
+	defaultSocketPath = "./firecracker.sock"
 )
 
 // Config represents runtime configuration parameters
 type Config struct {
 	FirecrackerBinaryPath string            `json:"firecracker_binary_path"`
-	SocketPath            string            `json:"socket_path"`
 	KernelImagePath       string            `json:"kernel_image_path"`
 	KernelArgs            string            `json:"kernel_args"`
 	RootDrive             string            `json:"root_drive"`

runtime/config.json.example

@@ -1,6 +1,5 @@
 {
   "firecracker_binary_path": "./firecracker",
-  "socket_path": "./firecracker.sock",
   "kernel_image_path": "vmlinux",
   "kernel_args": "console=ttyS0 noapic reboot=k panic=1 pci=off nomodules rw",
   "root_drive": "./vsock.img",

runtime/service.go

@@ -637,7 +637,7 @@ func (s *service) startVM(ctx context.Context,
 	}
 
 	cfg := firecracker.Config{
-		SocketPath:      s.config.SocketPath,
+		SocketPath:      defaultSocketPath,
 		VsockDevices:    []firecracker.VsockDevice{{Path: "root", CID: cid}},
 		KernelImagePath: s.config.KernelImagePath,
 		KernelArgs:      s.config.KernelArgs,
@@ -673,7 +673,7 @@ func (s *service) startVM(ctx context.Context,
 	cfg.Drives = driveBuilder.Build()
 	cmd := firecracker.VMCommandBuilder{}.
 		WithBin(s.config.FirecrackerBinaryPath).
-		WithSocketPath(s.config.SocketPath).
+		WithSocketPath(defaultSocketPath).
 		Build(ctx)
 	machineOpts := []firecracker.Opt{
 		firecracker.WithProcessRunner(cmd),