Deploying a simple linked container web app with Docker

July 6th, 2016 No comments

This is a simple guide on how to deploy a multi-container ‘linked’ web app using Docker.

If you have not yet installed or set up a Docker host to run the containers on, here is my guide on setting up a basic uBuntu 16.04 Docker host VM.

The ‘web app’ we’ll be looking at how to deploy will consist of two basic components – a MySQL database for the back-end, and a simple PHP script for the ‘web front-end’ which simply connects to the MySQL container and displays some info from a database table.


For the MySQL container we’ll be using the official Docker repo ‘mysql-server’ image, and for our web front-end, we’ll be creating our own Docker image using a custom Dockerfile we’ll craft ourselves, based on an uBuntu 15.04 image.

This means we’ll be covering the following Docker basics:

  • Running docker containers
  • Linking docker containers (more secure than exposing ports directly)
  • Creating custom docker images using a Dockerfile
  • Building a custom image

Start off by creating a new directory in your home directory called ‘web01’ to create and store the Dockerfile we’ll using to build our custom web front-end image. Then create an emtpy file called ‘Dockerfile’ in this directory and edit it using your favourite text editor. I’m using nano for this.



This is what your new Dockerfile should look like:


The commands do the following:

  • FROM – tells docker build to base this image build on the ubuntu:15.04 image
  • RUN – strings a few apt-get commands together to install apache, php5, and a few other tools like curl. This is important, as every RUN command in a Dockerfile creates a new image layer, and we don’t want our image to contain too many layers.
  • The last RUN command grabs the content from a gist I created which is a basic PHP script, and places it in the /var/www/html directory in the container, then deletes the default index.html file that apache places there. This is the script that will connect to our MySQL container and display some basic info (our basic ‘web app’).
  • EXPOSE – exposes port 80 so we can map this to our Docker host and access the website outside of the container.
  • CMD – runs the apache2 service with PID 1 when the container starts.

Now you can build the Dockerfile and create your own custom image, which is what will be used to start the web container later.

Use the following build command to build the new image from your custom Dockerfile

docker build -t=”web01image” ~/web01/Dockerfile

Run ‘docker images’ after the build completes and you should see the new image listed:


Next, you’ll run a new container using the official mysql-server image from the Docker repository. You won’t yet have this image locally, but the command will automatically download the image for you.

docker run –name db01 -e MYSQL_ROOT_PASSWORD=MyRootPassword -d mysql/mysql-server:latest

Note that I’ve called my container ‘db01’ and given it a root password of ‘MyRootPassword’. The -e parameter specifies that an environment variable called MYSQL_ROOT_PASSWORD inside the container should be given the value of ‘MyRootPassword’. The MySQL container then uses this environment variable to setup the root user for MySQL when the container starts.

Now that the database container is up and running (verify by running ‘docker ps’ to check its running), you can deploy the custom web container using your image you created above. In this docker run command, you’ll also link  the web container to the db01 container you previously started up using the –link parameter. This is important to link the two containers.

The web container will be given environment variables with information telling it about the networking config of the DB container. These environment variables will then be access by the simple web PHP script to tell it where to find the database server, and what credentials to use to connect.

docker run –name=web01 –link=db01:mysql -d -p=80:80 web01image

Important: notice that in the –link parameter, the name of the database/MySQL container is specified. Make sure you use the exact name you gave your MySQL database container here – this ensures that the linking of the two containers is correct. The last ‘web01image’ bit specifies to base the container you are running off of the newly built ‘web01image’.

The -p parameter maps the exposed port 80 in the container to port 80 on the docker host, so you’ll be able to access the website by using http://dockerhost:80

Check that the new web container and previously created MySQL container are running by using the ‘docker ps’ command.


Out of interest, this is what the PHP script looks like (this is what is downloaded and placed on the web container as a RUN build step in the Dockerfile you created above):

You can see the environment variables that the PHP script grabs (top of the script) to establish the database connection from the docker container. These environment variables are what are created and populated by linking the web container to the db container using the –link parameter.

Lastly, you may want to create a sample database, table and some data for the simple ‘web app’ to display after it connects to the database container. Issue the following ‘docker exec’ command, which will add the sample database, create a sample table, and add some sample data.

Make sure you change the ‘MyRootPassword’ bit to whatever root MySQL password you chose when you ran the MySQL container above, and ensure you run exec against the name of the MySQL container you chose (I used db01). Keep the database name and the rest of the command intact, as the PHP script relies on these staying the same.

docker exec db01 mysql -u root -pMyRootPassword -e “create database testdb1; use testdb1; CREATE TABLE events (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, name VARCHAR(20), signup_date DATE); INSERT INTO events (id,name,signup_date) VALUES (NULL, ‘MySpecialEvent’, ‘2016-06-11’);”

Finally, browse to http://dockerhostnameorip and you should see the simple PHP script display some basic info, stating it was able to connect to the MySQL server and display the sample data in the database.


Setting up a basic uBuntu 16.04 Docker host VM

July 6th, 2016 No comments

I’ve used this process multiple times to create quick Docker host VMs running on VMware Workstation in my home lab. It is important to note that although I’m using VMware Workstation, the type 2 hypervisor you use here is fairly unimportant. You could just as well use VirtualBox, or Fusion for this purpose.

Download the latest uBuntu 16.04 LTS server ISO from: (I believe 16.04 comes only in 64-bit, but make sure its 64-bit)

Create a new Virtual Machine for your Docker host using your type 2 hypervisor software (Workstation in my case).

Give the VM following hardware/spec:

  • OS – Linux/uBuntu 64bit
  • 1 or 2 vCPUs
  • 512 MB RAM
  • 9GB disk
  • 2 x vNICs (1st is set to the default NAT option and the 2nd should be set to Host-only)

Here is my VM’s setup:


Attach the uBuntu ISO and start the VM up.

Install a standard uBuntu OS using the text based installer, and just be sure to also install OpenSSH server when prompted for features to install. After the install completes, reboot, login with your user account you created during install, run ‘ifconfig’ to check the assigned IP address, and then use your favourite SSH client to connect to that IP. Using a PuTTy session will just make copy/pasting commands into your uBuntu VM easier.

Now you’ll install docker – the package includes both the docker server and client.


Run the commands above in sequence, and after the apt-get install docker-engine at the end, run ‘sudo service docker status’ to check that docker is running. You should see it listed as Active (running)

● docker.service – Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2016-07-06 21:20:39 BST; 2h 0min ago

Run a quick ‘docker info’ command to ensure that you get information back from Docker and that everything looks OK.


vCenter Server Appliance VM fails to boot with fsck failed message

November 5th, 2015 No comments


I had a storage outage to deal with recently, and after the datastores on this storage were taken down, a vCenter Server Appliance VM on the storage got some corrupted files and would not boot. Upon start up, I was greeted with this message:


The error message reads:

fsck failed.  Please repair manually and reboot.  The root
file system is currently mounted read-only.  To remount it
read-write do

After trying the mount command using the maintenance mode bash shell, I restarted and found that the appliance still did not boot properly. I found a thread on the VMware community forums where someone had the same issue and was able to run e2fsck to fix the disk issues. I tried this and found it fixed a whole heap of disk errors on the /dev/sda3 mount, but on restart I noticed more issues on the /dev/sdb2 mount, so I ran the e2fsck command again for this path, and was able to finally reboot the appliance successfully. The commands I ran to resolve were essentially:

  • mount -n -o remount,rw /
  • e2fsck -y /dev/sda3
  • e2fsck -y /dev/sdb2
  • CTRL-D to reboot after fixing the errors using e2fsck



VMware T10 compliant VAAI integration and HP P2000 G3 FC storage

November 5th, 2015 No comments


I’ve recently been updating firmware on some development and testing storage and found that the HP P2000 storage array firmware update TS251R004 and above enable the HP P2000 G3 FC enable T10 compliance for the hardware.


To quote VMware’s documentation on their VAAI implementation specific to T10 compliance:

The second required component can be referred to as a VAAI plug-in specific to the VAAI filter. It implements vendor-specific VAAI functions such as ATS, XCOPY and WRITE_SAME. There were different implementations of the VAAI block primitives in vSphere 4.1, but all of the primitives in vSphere 5.0 have been ratified by T10, so any array that is T10 compliant should be able to use VAAI.


This means that you no longer need to be running the HP P2000 VAAI plugin software directly on ESXi hosts. In fact, HP recommend you uninstall and remove the plugin software before you upgrade the firmware on these arrays, otherwise you could suffer from performance degradation and possible loss of access to datastores.

My process was to first of all login to all hosts and check for the presence of the VAAI plugin.

  • SSH into host as root, run find / -name hp_vaaip_p2000
  • Ensure that nothing comes up with the find command, if it does (you see something like this output: /usr/lib/vmware/vmkmod/hp_vaaip_p2000), then you should use this HP document to ensure it is removed correctly: – this will involve some setting changes, and removing claim rules as well as removal of the HP P2000 VAAI VIB itself.
  • After verifying nothing came up, check other hosts, and once happy all hosts are clear of the plugin, upgrade the firmware for the P2000 system.
  • Ideally reboot ESXi hosts after the firmware update and ensure access to datastores is still there. Check the hardware acceleration status of datastores – they should show up as “Supported”.

VMware vSphere community (free) health check options

October 14th, 2015 No comments

I recently did a presentation at the South West VMUG on VMware vSphere community (free) health check options. In my presentation I covered some of the options available out there at the moment such as:

  • vCheck (vSphere plugins)
  • vGhetto health check script
  • Miscellaneous PowerCLI / PowerShell options
Starting off the session in style - Intro in mspaint, running under Windows 3.1

Starting off the session in style – Intro in mspaint, running under Windows 3.1


The second half of my presentation I dived into a live PowerCLI and PowerShell demo where I demonstrated some PowerCLI basics to get any kind of information out of your vSphere environment using some of the core cmdlets. I demonstrated use of the core PowerCLI cmdlets used for retrieving VM, Host and Datastore information, how to use the pipeline in PowerShell, and taking a look at all properties on any PS object using the Get-Member cmdlet on the pipeline.

After covering these basics, I took a blank vCheck plugin template, and showed how easy it is to create your own custom plugins for vCheck should you find that the existing plugins don’t cover everything you need.

I’ve got a link to download the slides for the presentation below, and hopefully I’ll be able to find a recording of the PowerCLI / PowerShell live demo I did to attach to this post as a follow up.



If you’re based in the South West of the UK, be sure to check out and attend the next SW VMUG meeting!


vSphere 6.0 performance metric limitations in the database (config.vpxd.stats.maxQueryMetrics)

April 15th, 2015 No comments

A change I noticed right away between vSphere 5.5 and vSphere 6.0 is the introduction of a default limiter when it comes to performing database queries for performance metrics.

When querying vCenter 6.0 for performance data, there is a system in place by default that limits the number of entities that are included in a database query. As performance charts in the vSphere Web and C# client depend on this performance data, you may sometimes see an error when attempting to view overview or advanced charts because of this change.

In my case, I am using some custom code to query performance metrics using vSphere APIs and noticed the issue right away, as I was trying to gather a large amount of data.

VMware state that the reason for the change is to protect the vCenter database from receiving intensive or large queries.

If you wish to work around this, or remove the limit, you’ll need to introduce a new key/value pair advanced setting in the advanced settings area for your vCenter server instance. The key should be named “config.vpxd.stats.maxQueryMetrics” (without the quotes) and should have a value set of -1 to disable the limit. This could also be set to a value of 100 for example to limit the entities included in a database query to 100.

A further edit should be made to the web.xml file, however in my case I was not concerned with the limit affecting the client, as I was using the API, and making the first change seemed to do the trick for me.

You can read more about this setting by using this link to the official VMware KB article