Preventing Docker from manipulating iptables rules

By default, Docker manipulates iptables rules to provide network isolation: Chain FORWARD (policy DROP) target prot opt source destination DOCKER all — 0.0.0.0/0 0.0.0.0/0 […] Chain DOCKER (1 references) target prot opt source destination I don’t mind having my iptables rules for forwarding manipulated, but there is a caveat: when you expose a container (with … Continue reading Preventing Docker from manipulating iptables rules

Automatically update your Docker base images with watchtower

I’m an avid user of Docker containers, using base images pulled from the public registry DockedHub. As you may know, Docker containers are based on Docked base images, e.g. I run postgres containers that are based on Postgres base image. It occurs that base images could get updated by their respective author (in our case Postgres team) and pushed to DockerHub. … Continue reading Automatically update your Docker base images with watchtower

Reverse engineer a Docker run command from an existing container

During my usual backup routine, I wanted to gather how a Docker container I started a while ago was run, especially the docker run command; this is required in case I need to re-run that container and I want to preserve the options (e.g. env variables, ports, etc.). Let’s make an example. I run a … Continue reading Reverse engineer a Docker run command from an existing container

Docker and containerd on openSUSE: reaching the limit for cgroup (and how to overcome it!)

I recently encountered a limitation during an experiment I was conducting; after some trial and error, I recognized that the limitation was due to cgroups. But let’s start from the beginning. I open sourced docker-salt, a small pet project I had in mind in order to have a full blown setup for SaltStack: a master … Continue reading Docker and containerd on openSUSE: reaching the limit for cgroup (and how to overcome it!)

Getting started with cloud-init and CoreOS

Lately I’ve been experimenting with CoreOS, a Linux distribution that enforces containerization (I made some experiments with Docker and I’d say that this area is fun!). CoreOS layer of containerization was based Docker, but now that they moved to Rocket. Not only Rocket, though: CoreOS brings some curious innovations to lightweight Linux distributions like clusterization … Continue reading Getting started with cloud-init and CoreOS

Playing with Docker: tips and tricks to write effective Dockerfiles

Recently I have been playing with Docker containers, and I am sure you already know what Docker is. In this post I will describe what I have learnt while using Docker containers and preparing Dockerfiles. What is Docker? In a few words: Docker is a software to manage and run Linux containers in which you … Continue reading Playing with Docker: tips and tricks to write effective Dockerfiles