Every programmer at some point gets in touch with the Brainfuck programming language and how surprising is that very few instructions are needed to have a Turing complete language, 6 is the case of Brainfuck (plus other 2 for I/O operations). The language operates on a tape of memory cells using only increment, decrement, pointer movement, and conditional loop instructions. Writing a GCC frontend for it turns out to be a manageable project, and the result is a good template for understanding how language frontends hook into the GCC middle-end and optimization passes.

git rebase is one of my favorite git commands. It allows to update a set of local patches against another git branch and also to rework, through the -i flag, some previous patches. A lesser-known capability is the –exec flag, which runs an arbitrary shell command after each patch is applied during the rebase. Combined with the -X theirs merge strategy to silently resolve conflicts, this makes it straightforward to apply mechanical transformations — such as a symbol rename — across an entire patch series without manual intervention.

The main reason behind system containers was the inability to run Flannel in a Docker container as Flannel is required by Docker itself. CoreOS solved this chicken and egg problem by using another instance of Docker (called early-docker) that is used to setup only Etcd and Flannel. Atomic system containers take a different approach: instead of a second Docker daemon, they are managed directly by runc and systemd, so the dependency on Docker is removed entirely and the chicken-and-egg problem simply does not arise.

rpm-ostree, used together with OStree, is a powerful tool to generate immutable images for .rpm based systems, so why not use it for generating Docker images as well? rpm-ostree already has support for composing a container tree, but the steps to go from an OStree commit to a ready-to-run Docker image involve several manual operations. ostree-docker-builder is a small tool that automates this workflow, taking a JSON package description and producing a tagged Docker image with a minimal Dockerfile.

Coming as a surprise, this year we have got 4 students to work full-time during the summer on wget. More than all the students who have ever worked for wget before during a Summer of Code! The projects span a broad range of improvements: HSTS and FTPS security hardening, TCP Fast Open and conditional GET for performance, HTTP/2 support on top of nghttp2, and an expanded FTP test suite. Each student is expected to keep their work rebased on the current development branch to ease eventual integration.

This tutorial shows how to create a QCOW2 image that can be directly imported via virt-install to test out Fedora 22 Atomic starting from a custom OStree repo. The process involves composing an OStree repository from a Fedora Atomic tree definition, serving it over HTTP so the installer can reach it, then driving an unattended installation through a kickstart file. This gives you full control over the package set and tree composition rather than relying on a pre-built official image.

These are the steps to setup the current website in a Docker container. The setup uses docker-compose to declaratively describe a two-container application: a MySQL 5.5 database and a WordPress frontend. Docker links tie them together so that the web container can reach the database by hostname, without needing to hard-code any IP addresses or manage networking manually. A single docker-compose up command downloads the required images and starts both containers, with port 80 on the host forwarded into the WordPress container.