Revert "Remove --docker/dockershim support"

pkg/agent/config/config.go

@@ -321,10 +321,6 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 		logrus.SetLevel(logrus.DebugLevel)
 	}
 
-	if envInfo.Docker {
-		return nil, errors.New("--docker is no longer supported; to continue using docker, install cri-dockerd and set --container-runtime-endpoint")
-	}
-
 	info, err := clientaccess.ParseAndValidateToken(proxy.SupervisorURL(), envInfo.Token)
 	if err != nil {
 		return nil, err
@@ -437,6 +433,7 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 	}
 
 	nodeConfig := &config.Node{
+		Docker:                   envInfo.Docker,
 		SELinux:                  envInfo.EnableSELinux,
 		ContainerRuntimeEndpoint: envInfo.ContainerRuntimeEndpoint,
 		FlannelBackend:           controlConfig.FlannelBackend,
@@ -466,7 +463,7 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 	nodeConfig.AgentConfig.StrongSwanDir = filepath.Join(envInfo.DataDir, "agent", "strongswan")
 	nodeConfig.Containerd.Config = filepath.Join(envInfo.DataDir, "agent", "etc", "containerd", "config.toml")
 	nodeConfig.Containerd.Root = filepath.Join(envInfo.DataDir, "agent", "containerd")
-	if nodeConfig.ContainerRuntimeEndpoint == "" {
+	if !nodeConfig.Docker && nodeConfig.ContainerRuntimeEndpoint == "" {
 		switch nodeConfig.AgentConfig.Snapshotter {
 		case "overlayfs":
 			if err := containerd.OverlaySupported(nodeConfig.Containerd.Root); err != nil {
@@ -539,7 +536,7 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 		nodeConfig.AgentConfig.FlannelCniConfFile = envInfo.FlannelCniConfFile
 	}
 
-	if nodeConfig.ContainerRuntimeEndpoint == "" {
+	if !nodeConfig.Docker && nodeConfig.ContainerRuntimeEndpoint == "" {
 		nodeConfig.AgentConfig.RuntimeSocket = nodeConfig.Containerd.Address
 	} else {
 		nodeConfig.AgentConfig.RuntimeSocket = nodeConfig.ContainerRuntimeEndpoint

pkg/agent/flannel/setup_test.go

@@ -62,7 +62,7 @@ func Test_createFlannelConf(t *testing.T) {
 		var agent = config.Agent{}
 		agent.ClusterCIDR = stringToCIDR(tt.args)[0]
 		agent.ClusterCIDRs = stringToCIDR(tt.args)
-		var nodeConfig = &config.Node{ContainerRuntimeEndpoint: "", NoFlannel: false, SELinux: false, FlannelBackend: "vxlan", FlannelConfFile: "test_file", FlannelConfOverride: false, FlannelIface: nil, Containerd: containerd, Images: "", AgentConfig: agent, Token: "", Certificate: nil, ServerHTTPSPort: 0}
+		var nodeConfig = &config.Node{Docker: false, ContainerRuntimeEndpoint: "", NoFlannel: false, SELinux: false, FlannelBackend: "vxlan", FlannelConfFile: "test_file", FlannelConfOverride: false, FlannelIface: nil, Containerd: containerd, Images: "", AgentConfig: agent, Token: "", Certificate: nil, ServerHTTPSPort: 0}
 
 		t.Run(tt.name, func(t *testing.T) {
 			if err := createFlannelConf(nodeConfig); (err != nil) != tt.wantErr {

pkg/agent/run.go

@@ -101,7 +101,7 @@ func run(ctx context.Context, cfg cmds.Agent, proxy proxy.Proxy) error {
 		}
 	}
 
-	if nodeConfig.ContainerRuntimeEndpoint == "" {
+	if !nodeConfig.Docker && nodeConfig.ContainerRuntimeEndpoint == "" {
 		if err := containerd.Run(ctx, nodeConfig); err != nil {
 			return err
 		}

pkg/agent/run_linux.go

@@ -13,6 +13,7 @@ import (
 )
 
 const (
+	dockershimSock = "unix:///var/run/dockershim.sock"
 	containerdSock = "unix:///run/k3s/containerd/containerd.sock"
 )
 
@@ -21,7 +22,12 @@ const (
 func setupCriCtlConfig(cfg cmds.Agent, nodeConfig *config.Node) error {
 	cre := nodeConfig.ContainerRuntimeEndpoint
 	if cre == "" {
-		cre = containerdSock
+		switch {
+		case cfg.Docker:
+			cre = dockershimSock
+		default:
+			cre = containerdSock
+		}
 	}
 
 	agentConfDir := filepath.Join(cfg.DataDir, "agent", "etc")

pkg/agent/run_windows.go

@@ -7,12 +7,14 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/k3s-io/k3s/pkg/cli/cmds"
 	"github.com/k3s-io/k3s/pkg/daemons/config"
 )
 
 const (
+	dockershimSock = "npipe:////./pipe/docker_engine"
 	containerdSock = "npipe:////./pipe/containerd-containerd"
 )
 
@@ -20,10 +22,16 @@ const (
 // with the given data from config.
 func setupCriCtlConfig(cfg cmds.Agent, nodeConfig *config.Node) error {
 	cre := nodeConfig.ContainerRuntimeEndpoint
-	if cre == "" {
+	if cre == "" || strings.HasPrefix(cre, "npipe:") {
+		switch {
+		case cfg.Docker:
+			cre = dockershimSock
+		default:
+			cre = containerdSock
+		}
+	} else {
 		cre = containerdSock
 	}
-
 	agentConfDir := filepath.Join(cfg.DataDir, "agent", "etc")
 	if _, err := os.Stat(agentConfDir); os.IsNotExist(err) {
 		if err := os.MkdirAll(agentConfDir, 0700); err != nil {

pkg/cgroups/cgroups_linux.go

@@ -109,6 +109,9 @@ func CheckCgroups() (kubeletRoot, runtimeRoot string, controllers map[string]boo
 				// and thus need to set our kubelet root to something out of the context
 				// of `/user.slice` to ensure that `CPUAccounting` and `MemoryAccounting`
 				// are enabled, as they are generally disabled by default for `user.slice`
+				// Note that we are not setting the `runtimeRoot` as if we are running with
+				// `--docker`, we will inadvertently move the cgroup `dockerd` lives in
+				//  which is not ideal and causes dockerd to become unmanageable by systemd.
 				last := parts[len(parts)-1]
 				i := strings.LastIndex(last, ".scope")
 				if i > 0 {

pkg/cli/cmds/agent.go

@@ -123,7 +123,7 @@ var (
 	}
 	PauseImageFlag = cli.StringFlag{
 		Name:        "pause-image",
-		Usage:       "(agent/runtime) Customized pause image for containerd sandbox",
+		Usage:       "(agent/runtime) Customized pause image for containerd or docker sandbox",
 		Destination: &AgentConfig.PauseImage,
 		Value:       DefaultPauseImage,
 	}

pkg/daemons/config/types.go

@@ -43,6 +43,7 @@ var KubeletReservedPorts = map[string]bool{
 }
 
 type Node struct {
+	Docker                   bool
 	ContainerRuntimeEndpoint string
 	NoFlannel                bool
 	SELinux                  bool