Ramblings of a Unix Geek

I've been doing this for a long time... I ramble!

A look at Docker Swarm

In my previous entry I took a quick look at some of the Docker orchestration tools. I spent a bit of time poking at docker-compose and mentioned Swarm. In this entry I’m going to poke a little at Swarm; after all, it now comes as part of the platform and is a key foundation of Docker Enterprise Edition. Docker Swarm tries to take some of the concepts of a single host model and convert it into a cluster.

Simple Docker Orchestration

In earlier posts I looked at what a Docker image looks like and a dig into how it looks at runtime. In this entry I’m going to look at ways of running containers beyond a simple docker run command. docker-compose This is an additional program to be installed, but it’s very common in use. Basically, it takes a YAML configuration file. This can describe networks, dependencies, scaling factors, volumes etc etc.

Looking at how a Docker container runs

In the previous entry we looked at how a Docker container image is built. In this entry we’re going to look a little bit about how a container runs. Let’s take another look at the container we built last time, running apache: % cat Dockerfile FROM centos RUN yum -y update RUN yum -y install httpd CMD ["/usr/sbin/httpd","-DFOREGROUND"] % docker build -t web-server . % docker run --rm -d -p 80:80 -v $PWD/web_base:/var/www/html \ -v /tmp/weblogs:/var/log/httpd web-server 63250d9d48bb784ac59b39d5c0254337384ee67026f27b144e2717ae0fe3b57b % docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 63250d9d48bb web-server "/usr/sbin/httpd -.

What is a Docker container?

Container technology, specifically Docker, is becoming an important part of any enterprise. Even if you don’t have development teams targeting Docker you may have a vendor wanting to deliver their software in container form. I’m not so happy with that, but we’re going to have to live with it. In order to properly control the risk around this I feel it helps to have a feeling for the basics of what a Docker container is, and since I come from a technical background I like to look at it from a technology driven perspective.

Introduction to web SSL certificates

Last year I wrote about how I used Letsencrypt to handle the SSL certificates for this site. In this entry I’m going to take a step back and discuss the basics of what an SSL certificate is and the steps involved in managing them. There’s a lot of jargon involved, which can make this seem more complicated than it already is. Note that in this post I’m likely to use the words “SSL” and “TLS” interchangeably.

Data At Rest Encryption (DARE)

I’ve previous written about encryption and hashing and why things like customer passwords should never be encrypted. Sometimes, though, you need encryption because you need to get the raw data back. Now you can apply encryption at different layers. Some are easy; some are hard. What you need to be aware of, though, is what they protect against. There is no one-size-fits-all solution A standard app In a common scenario we may have an application that writes data to a database; that database persists data to disk.

Stuff changes; don't take things on faith, get the facts

A number of years back I saw a mail thread around Java performance. One person made the claim that Java was slow; if you wanted performant apps then write in a different language. This matched my experience, so I felt a little confirmation bias. However the reply really made me think; this may have been true 10 years ago (and, indeed, it’d been over 10 years since I’d done any real Java) but modern techniques meant that Java was perfectly fast.

Bottlenecks and SPOFs

If you’ve ever built any enterprise level system you’ll be aware of the needs of performance and resiliency. You may do performance testing on your application; you may have a backup server in a second data center; you may even do regular “Disaster Recovery tests”. And yet, despite all these efforts, your application fails in unexpected ways or isn’t as resilient as you planned. Your primary server dies, the DR server doesn’t work properly.

Building a home router

WARNING: technical content ahead! There’s also a tonne of config files, which make this page look longer than it really is, but hopefully they’ll help other people who want to do similar work. For many years I’ve been using variations of the Linksys WRT54G. I first switched to this router when freeware ROMs became available; I’ve used DD-WRT, Tomato, OpenWRT and others.

Cloud Inventory

One of the golden rules of IT security is that you need to maintain an accurate inventory of your assets. After all, if you don’t know what you have then how you can secure it? This may cover a list of physical devices (servers, routers, firewalls), virtual machines, software… An “asset” is an extremely flexible term and you need to look at it from various viewpoints to ensure you have good knowledge of your environment.