Updating WordPress and its plugins

Hi Everyone,

I’m having trouble trying to update plugins and WordPress with the sftp option.
When updating WordPress it ends with: “Unable to locate WordPress Root directory”.
When updating plugins it ends with: “Unable to locate WordPress Content directory (wp-content)”.

I’m running Ubuntu 14.04.2 with all updates.

The different WordPress sites are installed as a virtual host in separate folders under /var/www/html.
I have installed vsftpd as described here: https://help.ubuntu.com/lts/serverguide/ftp-server.html.
In addition, I have created a separate user account (being wp-update) pointing to /var/www/html as being the home for all the WordPress sites (represented as a folder for each virtual hosts). I’m able to login using FileZilla/sftp with this account and can create folders and files.
The (self-signed!) certificates are created with this:
https://www.server-world.info/en/note?os=Ubuntu_14.04&p=ssl

The vsftp log has multiple entries like the one below:
Tue May 26 18:54:22 2015 [pid 14175] [wp-update] DEBUG: Client “192.168.0.150”, “No SSL session reuse on data channel.”

When selecting the ssh2-option, the update was successful without entering any of the authentication keys. However, somehow, I’m not convinces that this is how it supposed to work?!

What am I missing here?