Backup and restore start-stop-daemon and initctl to prevent more serv…

…ices from starting during package installation

internal/helper/helper.go

@@ -20,8 +20,12 @@ import (
 )
 
 // define some functions that can be mocked by test cases
-var osRename = os.Rename
-var osRemove = os.Remove
+var (
+	osRename         = os.Rename
+	osRemove         = os.Remove
+	osWriteFile      = os.WriteFile
+	osutilFileExists = osutil.FileExists
+)
 
 func BoolPtr(b bool) *bool {
 	return &b
@@ -492,3 +496,42 @@ func RestoreResolvConf(chroot string) error {
 	}
 	return nil
 }
+
+const backupExt = ".REAL"
+
+// BackupReplace backup the target file and replace it with the given content
+// Returns the restore function.
+func BackupReplace(target string, content string) (func(error) error, error) {
+	backup := target + backupExt
+	if osutilFileExists(backup) {
+		// already backed up so do nothing
+		return nil, nil
+	}
+
+	if err := osRename(target, backup); err != nil {
+		return nil, fmt.Errorf("Error moving file \"%s\" to \"%s\": %s", target, backup, err.Error())
+	}
+
+	if err := osWriteFile(target, []byte(content), 0755); err != nil {
+		return nil, fmt.Errorf("Error writing to %s : %s", target, err.Error())
+	}
+
+	return genRestoreFile(target), nil
+}
+
+// genRestoreFile returns the function to be called to restore the backuped file
+func genRestoreFile(target string) func(err error) error {
+	return func(err error) error {
+		src := target + backupExt
+		if !osutilFileExists(src) {
+			return err
+		}
+
+		if tmpErr := osRename(src, target); tmpErr != nil {
+			tmpErr = fmt.Errorf("Error moving file \"%s\" to \"%s\": %s", src, target, tmpErr.Error())
+			return fmt.Errorf("%s\n%s", err, tmpErr)
+		}
+
+		return err
+	}
+}

internal/statemachine/classic_states.go

@@ -410,6 +410,28 @@ func (stateMachine *StateMachine) installPackages() error {
 		err = unsetDenyingPolicyRcD(err)
 	}()
 
+	restoreStartStopDaemon, err := backupReplaceStartStopDaemon(classicStateMachine.tempDirs.chroot)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		err = restoreStartStopDaemon(err)
+	}()
+
+	initctlPath := filepath.Join(classicStateMachine.tempDirs.chroot, "sbin", "initctl")
+
+	if osutil.FileExists(initctlPath) {
+		restoreInitctl, err := backupReplaceInitctl(classicStateMachine.tempDirs.chroot)
+		if err != nil {
+			return err
+		}
+
+		defer func() {
+			err = restoreInitctl(err)
+		}()
+	}
+
 	installPackagesCmds := generateAptCmds(stateMachine.tempDirs.chroot, classicStateMachine.Packages)
 
 	err = helper.RunCmds(installPackagesCmds, classicStateMachine.commonFlags.Debug)

internal/statemachine/helper.go

@@ -705,6 +705,31 @@ func dpkgDivert(baseDir string, target string) (*exec.Cmd, *exec.Cmd) {
 	return execCommand("chroot", divert...), execCommand("chroot", undivert...)
 }
 
+// backupReplaceStartStopDaemon backup start-stop-daemon and replace it with a fake one
+// Returns a restore function to put the original one in place
+func backupReplaceStartStopDaemon(baseDir string) (func(error) error, error) {
+	const startStopDaemonContent = `#!/bin/sh
+echo
+echo "Warning: Fake start-stop-daemon called, doing nothing"
+`
+
+	startStopDaemon := filepath.Join(baseDir, "sbin", "start-stop-daemon")
+	return helper.BackupReplace(startStopDaemon, startStopDaemonContent)
+}
+
+// backupReplaceInitctl backup initctl and replace it with a fake one
+// Returns a restore function to put the original one in place
+func backupReplaceInitctl(baseDir string) (func(error) error, error) {
+	const initctlContent = `#!/bin/sh
+if [ "$1" = version ]; then exec /sbin/initctl.REAL "$@"; fi
+echo
+echo "Warning: Fake initctl called, doing nothing"
+`
+
+	initctl := filepath.Join(baseDir, "sbin", "initctl")
+	return helper.BackupReplace(initctl, initctlContent)
+}
+
 // createPPAInfo generates the name for a PPA sources.list file
 // in the convention of add-apt-repository, and the contents
 // that define the sources.list in the DEB822 format