Switch runc and containerd startup to be entirely Go

At present they use a small shared function called "prepare"
that does the read-write remounts, that I will switch to doing overlay
mounts soon.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

pkg/containerd/Dockerfile

@@ -23,6 +23,7 @@ RUN cp bin/containerd bin/ctr bin/containerd-shim /usr/bin/
 ADD cmd /go/src/cmd
 RUN cd /go/src/cmd/service && ./skanky-vendor.sh $GOPATH/src/github.com/containerd/containerd
 RUN go-compile.sh /go/src/cmd/service
+RUN mkdir -p /etc/init.d && ln -s /usr/bin/service /etc/init.d/020-containerd
 
 WORKDIR /
 COPY . .
@@ -33,4 +34,5 @@ WORKDIR /
 COPY --from=alpine /usr/bin/containerd /usr/bin/ctr /usr/bin/containerd-shim /go/bin/service /usr/bin/
 COPY --from=alpine /etc/containerd/config.toml /etc/containerd/
 COPY --from=alpine /usr/share/zoneinfo/UTC /etc/localtime
+COPY --from=alpine /etc/init.d/ /etc/init.d/
 COPY etc etc/

pkg/containerd/Makefile

@@ -1,5 +1,5 @@
 IMAGE=containerd
 NETWORK=1
-DEPS=$(wildcard etc/init.d/*) $(wildcard cmd/service/*.go) etc/containerd/config.toml
+DEPS=$(wildcard cmd/service/*.go) etc/containerd/config.toml
 
 include ../package.mk

pkg/containerd/cmd/service/main.go

@@ -66,9 +66,8 @@ func main() {
 
 	args := flag.Args()
 	if len(args) < 1 {
-		fmt.Printf("Please specify a command.\n\n")
-		flag.Usage()
-		os.Exit(1)
+		systemInitCmd(args)
+		os.Exit(0)
 	}
 
 	switch args[0] {

pkg/containerd/cmd/service/prepare.go

@@ -0,0 +1,21 @@
+package main
+
+// Please note this file is shared between pkg/runc and pkg/containerd
+// Update it in both places if you make changes
+
+import (
+	"path/filepath"
+	"syscall"
+)
+
+func prepare(path string) error {
+	rootfs := filepath.Join(path, "rootfs")
+	if err := syscall.Mount(rootfs, rootfs, "", syscall.MS_BIND, ""); err != nil {
+		return err
+	}
+	// remount rw
+	if err := syscall.Mount("", rootfs, "", syscall.MS_REMOUNT, ""); err != nil {
+		return err
+	}
+	return nil
+}

pkg/containerd/cmd/service/start.go

@@ -58,6 +58,10 @@ func startCmd(args []string) {
 func start(service, sock, path, dumpSpec string) (string, uint32, string, error) {
 	rootfs := filepath.Join(path, service, "rootfs")
 
+	if err := prepare(filepath.Join(path, service)); err != nil {
+		return "", 0, "preparing rootfs", err
+	}
+
 	client, err := containerd.New(sock)
 	if err != nil {
 		return "", 0, "creating containerd client", err

pkg/containerd/etc/init.d/020-containerd

@@ -1,14 +0,0 @@
-#!/bin/sh
-
-# start service containers
-
-if [ -d /containers/services ]
-then
-	for f in $(find /containers/services -mindepth 1 -maxdepth 1 | sort)
-	do
-		/bin/mount --bind "$f/rootfs" "$f/rootfs"
-		mount -o remount,rw "$f/rootfs"
-	done
-fi
-
-service system-init