You should store your master key at a save place i.e., not on your notebook. When generating a new key subkey, don't copy your master key to your local file system. Rather tell GnuPG where your master key is and edit it there. Make sure that you use GnuPG version 2.
$ export GNUPGHOME=<where your master key is>
$ gpg --edit-key <your email address>
In the menu run
expire to change the expiration date of your master key if
necessary. Add two additional keys, one for encryption and one for signing,
addkey and the following menus. Quit and save the new subkeys with
Export the keys with the following command:
$ gpg --armor --export-secret-subkeys > secret-subkeys.asc
Copy the file
secret-subkeys.asc to your notebook (or any other device where
you need your keys) and import them with
gpg --import secret-subkeys.asc.