engine: nspawn: Add an nspawn example with an improved exec

This adds the cwd fields to exec, better error messages to svc (which is
nested in nspawn) and a fancier nspawn example!

engine/resources/exec.go

@@ -47,11 +47,14 @@ type ExecRes struct {
 	init *engine.Init
 
 	Cmd        string  `yaml:"cmd"`        // the command to run
+	Cwd        string  `yaml:"cwd"`        // the dir to run the command in (empty means use `pwd` of command)
 	Shell      string  `yaml:"shell"`      // the (optional) shell to use to run the cmd
 	Timeout    int     `yaml:"timeout"`    // the cmd timeout in seconds
 	WatchCmd   string  `yaml:"watchcmd"`   // the watch command to run
+	WatchCwd   string  `yaml:"watchcwd"`   // the dir to run the watch command in (empty means use `pwd` of command)
 	WatchShell string  `yaml:"watchshell"` // the (optional) shell to use to run the watch cmd
 	IfCmd      string  `yaml:"ifcmd"`      // the if command to run
+	IfCwd      string  `yaml:"ifcwd"`      // the dir to run the if command in (empty means use `pwd` of command)
 	IfShell    string  `yaml:"ifshell"`    // the (optional) shell to use to run the if cmd
 	User       string  `yaml:"user"`       // the (optional) user to use to execute the command
 	Group      string  `yaml:"group"`      // the (optional) group to use to execute the command
@@ -122,7 +125,7 @@ func (obj *ExecRes) Watch() error {
 			cmdArgs = []string{"-c", obj.WatchCmd}
 		}
 		cmd := exec.Command(cmdName, cmdArgs...)
-		//cmd.Dir = "" // look for program in pwd ?
+		cmd.Dir = obj.WatchCwd // run program in pwd if ""
 		// ignore signals sent to parent process (we're in our own group)
 		cmd.SysProcAttr = &syscall.SysProcAttr{
 			Setpgid: true,
@@ -208,7 +211,6 @@ func (obj *ExecRes) CheckApply(apply bool) (bool, error) {
 	// have a chance to execute, and all without the check of obj.Refresh()!
 
 	if obj.IfCmd != "" { // if there is no onlyif check, we should just run
-
 		var cmdName string
 		var cmdArgs []string
 		if obj.IfShell == "" {
@@ -224,6 +226,7 @@ func (obj *ExecRes) CheckApply(apply bool) (bool, error) {
 			cmdArgs = []string{"-c", obj.IfCmd}
 		}
 		cmd := exec.Command(cmdName, cmdArgs...)
+		cmd.Dir = obj.IfCwd // run program in pwd if ""
 		// ignore signals sent to parent process (we're in our own group)
 		cmd.SysProcAttr = &syscall.SysProcAttr{
 			Setpgid: true,
@@ -266,7 +269,7 @@ func (obj *ExecRes) CheckApply(apply bool) (bool, error) {
 		cmdArgs = []string{"-c", obj.Cmd}
 	}
 	cmd := exec.Command(cmdName, cmdArgs...)
-	//cmd.Dir = "" // look for program in pwd ?
+	cmd.Dir = obj.Cwd // run program in pwd if ""
 	// ignore signals sent to parent process (we're in our own group)
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Setpgid: true,
@@ -373,6 +376,9 @@ func (obj *ExecRes) Compare(r engine.Res) bool {
 	if obj.Cmd != res.Cmd {
 		return false
 	}
+	if obj.Cwd != res.Cwd {
+		return false
+	}
 	if obj.Shell != res.Shell {
 		return false
 	}
@@ -382,12 +388,18 @@ func (obj *ExecRes) Compare(r engine.Res) bool {
 	if obj.WatchCmd != res.WatchCmd {
 		return false
 	}
+	if obj.WatchCwd != res.WatchCwd {
+		return false
+	}
 	if obj.WatchShell != res.WatchShell {
 		return false
 	}
 	if obj.IfCmd != res.IfCmd {
 		return false
 	}
+	if obj.IfCwd != res.IfCwd {
+		return false
+	}
 	if obj.IfShell != res.IfShell {
 		return false
 	}

engine/resources/svc.go

@@ -349,7 +349,12 @@ func (obj *SvcRes) CheckApply(apply bool) (checkOK bool, err error) {
 	if &status == nil {
 		return false, fmt.Errorf("systemd service action result is nil")
 	}
-	if status != "done" {
+	switch status {
+	case "done":
+		// pass
+	case "failed":
+		return false, fmt.Errorf("svc failed (selinux?)")
+	default:
 		return false, fmt.Errorf("unknown systemd return string: %v", status)
 	}
 

examples/lang/nspawn0.mcl

@@ -0,0 +1,31 @@
+# setenforce Permissive
+
+import "fmt"
+
+$codename = "stretch"
+$baserepo = "https://deb.debian.org/debian/"
+$rootpath = "/var/lib/machines/"
+
+pkg "debootstrap" {
+	state => "newest",
+}
+
+$dir = $codename + "-" + "nspawn" # dir name
+$cmd = fmt.printf("debootstrap --include=systemd-container %s %s %s", $codename, $dir, $baserepo)
+exec "debootstrap-" + $codename {
+	cwd => $rootpath,
+
+	shell => "/bin/bash",
+	cmd => $cmd,
+
+	ifshell => "/bin/bash",
+	ifcmd => fmt.printf("test ! -d %s", $rootpath),
+
+	Depend => Pkg["debootstrap"],
+}
+
+nspawn $dir {
+	state => "running",
+
+	Depend => Exec["debootstrap-" + $codename],
+}