I created pre-installed Ubuntu Server 15.04 64bit Virtualbox image to be used for various server side setups.

It can be freely downloaded and used by you.
all packages were updated to the current date (9/5/15).
openssh server was installed and set to default port

File can be downloaded from here:

Link: UbuntuServer1504VboxImage.tar.bz2
MD5: eff64b08b8e2fc4ceb668a4e1a62b82d

The credentials are:
user: serveradmin
password: 123456

Please change the password immediately after you download the image for obvious security reasons.

You should change the following after booting

hostname (preset to “ubuntu”)
Date/Time (preset to Jerusalem – GMT+2)
Language / Keyboard setup (preset US English)

Notes:
1. Virtualbox Guest util is not installed.
2. The image was created with VirtualBox 4.3.26r98988
3. Audio / USB / serial port are disabled
4. HD size was set to 128GB, resized dynamically.