cmd/initContainer: Simplify code by removing a function parameter

Until now, configureUsers() was pushing the burden of deciding whether
to add a new user or modify an existing one on the callers, even though
it can trivially decide itself.  Involving the caller loosens the
encapsulation of the user configuration logic by spreading it across
configureUsers() and it's caller, and adds an extra function parameter
that needs to be carefully set and is vulnerable to programmer errors.

Fallout from 9ea6fe5

containers#1356

src/cmd/initContainer.go

@@ -236,24 +236,12 @@ func initContainer(cmd *cobra.Command, args []string) error {
 		}
 	}
 
-	if _, err := user.Lookup(initContainerFlags.user); err != nil {
-		if err := configureUsers(initContainerFlags.uid,
-			initContainerFlags.user,
-			initContainerFlags.home,
-			initContainerFlags.shell,
-			initContainerFlags.homeLink,
-			false); err != nil {
-			return err
-		}
-	} else {
-		if err := configureUsers(initContainerFlags.uid,
-			initContainerFlags.user,
-			initContainerFlags.home,
-			initContainerFlags.shell,
-			initContainerFlags.homeLink,
-			true); err != nil {
-			return err
-		}
+	if err := configureUsers(initContainerFlags.uid,
+		initContainerFlags.user,
+		initContainerFlags.home,
+		initContainerFlags.shell,
+		initContainerFlags.homeLink); err != nil {
+		return err
 	}
 
 	if utils.PathExists("/etc/krb5.conf.d") && !utils.PathExists("/etc/krb5.conf.d/kcm_default_ccache") {
@@ -386,9 +374,7 @@ func initContainerHelp(cmd *cobra.Command, args []string) {
 	}
 }
 
-func configureUsers(targetUserUid int,
-	targetUser, targetUserHome, targetUserShell string,
-	homeLink, targetUserExists bool) error {
+func configureUsers(targetUserUid int, targetUser, targetUserHome, targetUserShell string, homeLink bool) error {
 	if homeLink {
 		if err := redirectPath("/home", "/var/home", true); err != nil {
 			return err
@@ -400,45 +386,45 @@ func configureUsers(targetUserUid int,
 		return fmt.Errorf("failed to get group for sudo: %w", err)
 	}
 
-	if targetUserExists {
-		logrus.Debugf("Modifying user %s with UID %d:", targetUser, targetUserUid)
+	if _, err := user.Lookup(targetUser); err != nil {
+		logrus.Debugf("Adding user %s with UID %d:", targetUser, targetUserUid)
 
-		usermodArgs := []string{
-			"--append",
+		useraddArgs := []string{
 			"--groups", sudoGroup,
-			"--home", targetUserHome,
+			"--home-dir", targetUserHome,
+			"--no-create-home",
 			"--shell", targetUserShell,
 			"--uid", fmt.Sprint(targetUserUid),
 			targetUser,
 		}
 
-		logrus.Debug("usermod")
-		for _, arg := range usermodArgs {
+		logrus.Debug("useradd")
+		for _, arg := range useraddArgs {
 			logrus.Debugf("%s", arg)
 		}
 
-		if err := shell.Run("usermod", nil, nil, nil, usermodArgs...); err != nil {
-			return fmt.Errorf("failed to modify user %s with UID %d: %w", targetUser, targetUserUid, err)
+		if err := shell.Run("useradd", nil, nil, nil, useraddArgs...); err != nil {
+			return fmt.Errorf("failed to add user %s with UID %d: %w", targetUser, targetUserUid, err)
 		}
 	} else {
-		logrus.Debugf("Adding user %s with UID %d:", targetUser, targetUserUid)
+		logrus.Debugf("Modifying user %s with UID %d:", targetUser, targetUserUid)
 
-		useraddArgs := []string{
+		usermodArgs := []string{
+			"--append",
 			"--groups", sudoGroup,
-			"--home-dir", targetUserHome,
-			"--no-create-home",
+			"--home", targetUserHome,
 			"--shell", targetUserShell,
 			"--uid", fmt.Sprint(targetUserUid),
 			targetUser,
 		}
 
-		logrus.Debug("useradd")
-		for _, arg := range useraddArgs {
+		logrus.Debug("usermod")
+		for _, arg := range usermodArgs {
 			logrus.Debugf("%s", arg)
 		}
 
-		if err := shell.Run("useradd", nil, nil, nil, useraddArgs...); err != nil {
-			return fmt.Errorf("failed to add user %s with UID %d: %w", targetUser, targetUserUid, err)
+		if err := shell.Run("usermod", nil, nil, nil, usermodArgs...); err != nil {
+			return fmt.Errorf("failed to modify user %s with UID %d: %w", targetUser, targetUserUid, err)
 		}
 	}