Use /etc/sudoers.d/ to configure admin user sudo rights

plugins/admin-user-tasks/create-user

@@ -1,11 +1,14 @@
 #!/bin/bash
 admin_username='admin'
 
-# Create the user and add him to the 'sudo' group
+# Create the user
 chroot $imagedir useradd --create-home --shell /bin/bash $admin_username
 
 # Allow ec2-user to use sudo without a password
-sed -i "/^root\tALL=(ALL) ALL/a $admin_username\tALL=(ALL) NOPASSWD: ALL" $imagedir/etc/sudoers
+cat > $imagedir/etc/sudoers.d/99_admin <<EOF
+$admin_username ALL=(ALL) NOPASSWD:ALL
+EOF
+chmod 440 $imagedir/etc/sudoers.d/99_admin
 
 # ec2-get-credentials should add the pubkey to the new user account and not root
 sed -i "s/^username='root'/username='$admin_username'/" $imagedir/etc/init.d/ec2-get-credentials