Pages tagged with 'Docker'

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Exposing Docker's internal DNS with CoreDNS

2024-01-17
6 minutes

Whilst Docker is a containerisation technology, it's not just about running applications - there's also networking. When you add a container to a docker network, it magically becomes discoverable by other containers on the same network with DNS. All containers use Docker's magical internal DNS server to achieve this. However,…

Library Database

Upgrading Databases in Docker

2021-12-23
5 minutes

For me, every Monday is updates day. All machines have OS updates, and the handful which run docker get their containers pulled. However, pulling containers merely updates the underlying container OS, or maybe patch versions of the application (because I do container pinning properly). Updating actual versions can be a…

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Docker in LXC

Docker is a great containerization technology for running applications. It keeps multiple applications completely isolated from each other, only allowing connections exactly when you tell them to. But what if you’re on a hypervisor? You want your host OS to be as lean as possible (else it defeats the point),…

Freight Containers on a Ship

Backing up and restoring Docker containers

You should back up your data, properly! If you’re not, you’re playing a dangerous game with fate. Computers are pretty reliable, but they also go wrong, often. You should always backup your files, but backing up a containerized application isn’t quite as simple. A container is 3 things:ConfigurationVolumesNetworking The point…

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Increase your Docker IP space

Recently, I started setting up a new application on my docker host. It was late in the day, and I just wanted to get something up and working to play around with. Just my luck, I was met with wonderfully cryptic error:ERROR: could not find an available, non-overlapping IPv4 address…

Container processes shouldn't run as root!

Docker containers, and containers as a whole, are really just a regular program wrapped in some extra protections provided by the kernel (namely cgroups etc) to create isolation, and other interesting features. Unlike VMs, containers run closer to the host operating system, so close they use the same kernel, meaning…

Keeping your Docker containers up to date

Last year, I switched all of my hosting from arbitrarily installed packages to Docker. This made installing and configuring incredibly simple, but updating a little less defined. Whilst Docker itself is updated through the system package manager (probably), the containers themselves aren’t. Docker container versions are known as “tags”, and…