Dropbox and Google Drive are very useful tools: Without much effort, you can synchronize data between your computers, push data from your cellphone to your network, or collaborate with friends and colleagues.

However, there's a catch: You need to hand over control of your data. Without encryption with a self-generated key (e.g., as provided by an alternative like SpiderOak [1]), the provider could access the data stored in the cloud at any time. This problem can only be solved by an encrypted container in the cloud – or a self-hosted ownCloud installation [2]. However, not everyone has the knowledge and the resources to set up this kind of environment and operate it reliably.

AeroFS [3] offers a genuine alternative, which combines the convenience of Dropbox with the benefits of a private cloud. The service was opened to the public at the beginning of April 2012.

AeroFS, Your Home Cloud

AeroFS, unlike ownCloud, is not free software but a commercial service [4]. Groups of up to three members and one external worker (who can also synchronize data but cannot access user management) can use AeroFS free of charge. Groups of up to 50 members pay US$ 10 per month. If you need more users, you need to contact AeroFS directly. However AeroFS does not offer a hosted service; instead, clients linked to a user account synchronize their encrypted data directly (peer-to-peer). The basic configuration thus does without a central server in the ubiquitous data cloud.

The web front end of the AeroFS website (Figure 1) is used only to manage the user account. All the work is done by a client (Figure 2), which is available for Linux [5], Mac OS X, and Windows. Additionally, AeroFS now also offers an app for Android.

Figure 1: The AeroFS web front end is only used to administer your account. You have no access to your data here – in contrast to Dropbox.

Figure 2: The AeroFS client's look and feel is strongly reminiscent of Dropbox. It synchronizes changes to the data with all clients in the background.

Setting Up AeroFS

The client installation takes just a few moments on Ubuntu systems thanks to a DEB package. In the lab, the package installed without problems on a system with Debian "wheezy." For users of other distributions, AeroFS offers .tgz archives with statically compiled binaries. Just unzip to a suitable location (e.g., in /usr/local/bin) and then run directly.

Synchronization works on the LAN without Internet access. As with Dropbox, you store the data to be sync'd in the monitored AeroFS directory. Immediately afterward, AeroFS quickly distributes the files to all the computers on your home LAN, on which the AeroFS client is also installed for your user account. If an additional client is only accessible via the Internet, synchronization takes a little longer. Besides the default folders, you can freely select additional folders to synchronize.

Like Dropbox, AeroFS also versions filesystem changes. So, if you accidentally delete or modify files, you can simply restore the previous versions of data shared via AeroFS. Because AeroFS itself does not offer a hosting service, there are no size restrictions. If necessary, you can sync terabytes of files between your computers via AeroFS.

AeroFS Team Server

In P2P mode, a full sync only works if all participating computers are running and have access to the LAN or the Internet. If you collaborate with someone on the other side of the globe, you might wait in vain for recent changes to make their way to your own computer via AeroFS: Your co-worker might already have shut down their computer for the evening.

For such cases, AeroFS offers its own AeroFS Team server [6] in versions for Linux, Mac OS X, and Windows. You can set this up on a computer at home or even on a root server on the Internet and thus practically create your own Dropbox. On Linux, the server officially supports Ubuntu as of version 8.04 with a DEB package that you can install using the package manager. Other distributions have .tgz archives with executable binaries.

On an Ubuntu server, you can use dpkg to install the downloaded DEB package and then run apt-get to resolve any missing dependencies (Listing 1). On an Ubuntu desktop, Software Center handles the installation of the package, including any post-install tasks.

$ sudo dpkg -i aerofsts-installer.deb
$ sudo apt-get install -f

On a root server with Debian "squeeze," which I used for test purposes, I needed to install the necessary dependencies manually up front and then unpack the executable binaries from the .tgz archive in /usr/local/bin/ (Listing 2). AeroFS does not come with its own installation routine as of this writing.

sudo apt-get install coreutils file default-jre sharutils procps
sudo tar xzf aerofsts-installer.tgz -C /usr/local/bin/

After completing the install, you need to run

aerofsts-gui

on a computer with a graphical environment. On servers that can only be accessed via SSH, you can use aerofsts-cli for a headless client. Call the client to configure your AeroFS account in the foreground (Figure 3), then enter your AeroFS credentials, the path to your data, and the name of the installation. To test, you can outsource the data to Amazon S3 storage. This completes the configuration of the service. Active clients now automatically upload the respective data to the Team Server you just set up.

Figure 3: The free Team Server makes AeroFS a self-hosted alternative to Dropbox, Google Drive, and the like.

Thus far, AeroFS offers no init scripts that automatically start up the server at boot time. As an alternative, you can launch the service in a screen instance. To do this automatically at boot time, enter the command line on a Debian or Ubuntu system in /etc/rc.local. The following command takes you to the screen session from a terminal:

$ screen -dmS AeroFS /usr/local/bin/aerofs/aerofsts-cli

If you want to use AeroFS as a long-term solution, it makes sense to create a separate user account on the server. Because the Team Server does not open any ports within the area reserved for root, the AeroFS user does not need any additional rights.

If you need more computing power or redundancy in the event of a server failure, you can interconnect several AeroFS Team Servers simply by installing the service on other computers under the same account name. All data is synchronized immediately between the servers and kept up to date.