step011: run command

.gitignore

@@ -0,0 +1,2 @@
+.idea
+.vscode

go.mod

@@ -0,0 +1,15 @@
+module upod
+
+go 1.22.1
+
+require (
+	github.com/sirupsen/logrus v1.9.3
+	github.com/spf13/cast v1.6.0
+	github.com/spf13/cobra v1.8.0
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
+)

go.sum

@@ -0,0 +1,36 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
+github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
+github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
+github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/spf13/cast v1.6.0 h1:GEiTHELF+vaR5dhz3VqZfFSzZjYbgeKDpBxQVS4GYJ0=
+github.com/spf13/cast v1.6.0/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
+github.com/spf13/cobra v1.8.0 h1:7aJaZx1B85qltLMc546zn58BxxfZdR/W22ej9CFoEf0=
+github.com/spf13/cobra v1.8.0/go.mod h1:WXLWApfZ71AjXPya3WOlMsY9yMs7YeiHhFVlvLyhcho=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/cmd/init.go

@@ -0,0 +1,6 @@
+package cmd
+
+func init() {
+	initRootCommand()
+	initRunCommand()
+}

internal/cmd/root.go

@@ -0,0 +1,16 @@
+package cmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var (
+	rootCommand = &cobra.Command{
+		Use:   "upod",
+		Short: "upod is a simple container runtime implementation",
+	}
+)
+
+func initRootCommand() {
+
+}

internal/cmd/run.go

@@ -0,0 +1,44 @@
+package cmd
+
+import (
+	"errors"
+	"os"
+	"upod/internal/container"
+	"upod/internal/log"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	runCommand = &cobra.Command{
+		Use:   "run",
+		Short: "upod run [OPTIONS] IMAGE [COMMAND] [ARG...]",
+		RunE: func(ctx *cobra.Command, args []string) error {
+			var (
+				err error
+			)
+
+			log.Debug("runCommand: args=%v", args)
+
+			if len(args) == 0 {
+				return errors.New("upod run requires at least 1 argument")
+			}
+
+			cmd := container.NewParentProcess(true, args[0])
+
+			if err = cmd.Start(); err != nil {
+				return err
+			}
+
+			cmd.Wait()
+
+			os.Exit(0)
+
+			return nil
+		},
+	}
+)
+
+func initRunCommand() {
+	rootCommand.AddCommand(runCommand)
+}

internal/cmd/start.go

@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"context"
+	"os"
+	"upod/internal/container"
+	"upod/internal/log"
+)
+
+func Start(ctx context.Context) error {
+
+	if len(os.Args) >= 3 && os.Args[1] == "init" {
+		log.Debug("cmd.Start: init args=%v", os.Args)
+
+		container.RunContainerInitProcess(os.Args[2], os.Args[2:])
+	}
+
+	return rootCommand.ExecuteContext(ctx)
+}

internal/container/new.go

@@ -0,0 +1,32 @@
+package container
+
+import (
+	"os"
+	"os/exec"
+	"syscall"
+)
+
+// NewParentProcess 启动一个新进程
+/*
+这里是父进程，也就是当前进程执行的内容。
+1.这里的/proc/se1f/exe调用中，/proc/self/ 指的是当前运行进程自己的环境，exec 其实就是自己调用了自己，使用这种方式对创建出来的进程进行初始化
+2.后面的args是参数，其中init是传递给本进程的第一个参数，在本例中，其实就是会去调用initCommand去初始化进程的一些环境和资源
+3.下面的clone参数就是去fork出来一个新进程，并且使用了namespace隔离新创建的进程和外部环境。
+4.如果用户指定了-it参数，就需要把当前进程的输入输出导入到标准输入输出上
+*/
+func NewParentProcess(tty bool, command string) *exec.Cmd {
+	args := []string{"init", command}
+	cmd := exec.Command("/proc/self/exe", args...)
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Cloneflags: syscall.CLONE_NEWUTS | syscall.CLONE_NEWPID | syscall.CLONE_NEWNS |
+			syscall.CLONE_NEWNET | syscall.CLONE_NEWIPC,
+	}
+
+	if tty {
+		cmd.Stdin = os.Stdin
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+	}
+
+	return cmd
+}

internal/container/run.go

@@ -0,0 +1,35 @@
+package container
+
+import (
+	"os"
+	"syscall"
+	"upod/internal/log"
+)
+
+// RunContainerInitProcess 启动容器的init进程
+/*
+这里的init函数是在容器内部执行的，也就是说，代码执行到这里后，容器所在的进程其实就已经创建出来了，
+这是本容器执行的第一个进程。
+使用mount先去挂载proc文件系统，以便后面通过ps等系统命令去查看当前进程资源的情况。
+*/
+func RunContainerInitProcess(command string, args []string) error {
+	var (
+		err error
+	)
+
+	log.Debug("RunContainerInitProcess: command=%s args=%v", command, args)
+
+	syscall.Mount("", "/", "", syscall.MS_PRIVATE|syscall.MS_REC, "")
+
+	defaultMountFlags := syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NODEV
+
+	_ = syscall.Mount("proc", "/proc", "proc", uintptr(defaultMountFlags), "")
+
+	argv := []string{command}
+
+	if err = syscall.Exec(command, argv, os.Environ()); err != nil {
+		return err
+	}
+
+	return nil
+}

internal/log/log.go

@@ -0,0 +1,19 @@
+package log
+
+import (
+	"os"
+
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/cast"
+)
+
+func init() {
+	if cast.ToBool(os.Getenv("UPOD_DEBUG")) {
+		logrus.SetLevel(logrus.DebugLevel)
+	}
+
+}
+
+func Debug(msg string, args ...any) {
+	logrus.Debugf(msg, args...)
+}

main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"context"
+	"upod/internal/cmd"
+)
+
+func main() {
+	cmd.Start(context.TODO())
+}