Cannot connect to the Docker daemon – fixed!

containersA quick note this time around: After installing Docker on my Linux Mint laptop, I wanted to be able to run it with my normal user account and not have to SUDO every time I wanted to start a container. (Please be advised that doing so can be considered a HUGE security hole, but since I am just testing Docker, I was willing to risk it).

In order to do this, all of the documentation I found said to create a Docker group, and then add my user account to that group, and restart. This is fairly simple to accomplish with the GUI Users and Groups tool. The Docker daemon then uses that group to see if the user account has permissions to start Docker and connect to the daemon. The result? I would get this error: Cannot connect to the Docker daemon. Is ‘docker daemon’ running on this hostAfter trying several things, I finally found the solution.

  1. From a terminal prompt run this command:
    echo $DOCKER_HOST

    You should see a line indicating your Docker host is set to an IP address. You will need to clear it.

  2. At the terminal prompt, switch  to your home folder:
    cd ~
  3. Now, edit your shell profile:
     nano ./.profile
  4. Look for a line like this:
     export DOCKER_HOST=tcp://
  5. Add a comment marker (#) before it or delete the line completely. Save your profile file and exit.
  6. Restart your system, and you should now be able to run Docker using your normal user account.



Install the Tor Browser on Linux

DCF 1.0

The TOR project was started by United States Naval Research Lab employees in the early part of the 21st century as a way to protect intelligence communications  online. It was open sourced in 2004, and continues to be supported by the Electronic Frontier Foundation. As privacy as continued to decline on the Internet, interest in the Tor Browser and Tor project has increased. For more information on TOR see this recent article at

I would like to note that I don’t support or condone the use of TOR for illicit or illegal purposes, but for those who feel that their privacy is important , I am providing these instructions for how to install the Tor Browser on Linux. These instructions should work for most Linux distros.

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Cassandra Installation on Linux Mint

Cassandra_logoNoSQL databases are multiplying faster that anyone could have imagined when Google released their Google File System and MapReduce papers in 2003 and 2004 – the inspiration for a host of NoSQL database developers.

The NoSQL project that became Apache Cassandra was originally developed at Facebook as the back-end for their Inbox Search feature. It was released as open source in July 2008 and later moved to the Apache Foundation. Gaining in popularity in the intervening time,  the website now ranks Cassandra the eighth most popular data management system.

Setting up a development version of Cassandra on Linux Mint is pretty straightforward, and this tutorial will walk through the process. At the time of this writing, Cassandra 3.0.1 had just been released. It requires Java 8 or later and at least 8GB of RAM. Version 2.2.4 is available as the most current stable version, which will run with Java 6 or later with 4GB or RAM. If you intend to use DataStax’s OpsCenter management tool be aware that it does not currently support either version.

To illustrate the installation of OpsCenter I will be covering the older Cassandra version 2.1 which IS supported by OpsCenter. DataStax notes on their website that the next version of OpsCenter will support Cassandra 2.2 and 3.0. The difference between installing version 2.2 or 3.0 is minimal and I’ll note that as we process. Also, be aware that the Linux Mint update center may try to upgrade your system to 3.0 once you are complete.

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Use Linux Mint as a Server

mortar-mintLinux Mint has been consistently at the top of the DistroWatch top ten list for more than a year due I am sure to its ease of use and solid performance. As a general purpose distribution, Mint is offered with several different desktop environments, but interestingly, no separate server distribution. However, it is possible to configure Mint as a server, and this article covers the basic setup I follow to configure a Mint system for development server purposes.

As a warning however, be sure to lock your system down with appropriate security precautions before using one as a production server. Below are the standard steps I use while configuring Mint for development systems. Because I follow these steps pretty regularly, I have pulled them out as a separate article, and will link back to this as necessary for any future tutorials. Continue reading