Basic Docker commands

Just a list of docker commands that I've found quite useful so far.

List the containers available locally:

docker ps -a

Just the container IDs:

docker ps -a -q

Filter the running containers:

docker ps -a -q | grep Up

or simply:

docker ps -q

Build an image:

docker build -t <user>/<image name> .

Run a container from an image, and execute bash shell:

docker run -i -t <user>/<image name> /bin/bash

Run a container from an image, in background, linking ports:

docker run -d -p <host port>:<container port> <user>/<image name>

(You can use -p multiple times, e.g. when the container exposes more than one port)

Show logs of running container:

docker logs <container id>

Stop/start/restart container:

docker stop/start/restart <container id>

UPDATE - Stop running container with a single command:

docker ps -a|grep Up|awk '{ print $1 }'|xargs docker stop

UPDATE - The reason why I'm not using sudo to run these commands is that I added my user to the docker group, e.g.:

sudo usermod -aG docker

I hope you find this useful.

(Docker 1.1.2 on Ubuntu 14.04)

About ICE negotiation

Disclaimer: I wrote this article on March 2022 while working with Subspace, and the original link is here: https://subspace.com/resources/ice-negotiation . This post in my personal blog is a way to ensure it doesn't get lost. There is nothing service-specific in it, I've made only minor edits and I hope it can be a good technical reference on the topic. WebRTC is a set of protocols that allow applications, typically running on Web browsers, to exchange media (audio, video, data) with other entities. Before media can flow, however, the WebRTC entities need to discover what type of connection is possible, and among the possible connections, what’s the best to be used. This needs to happen as fast as possible, so that users can perceive the service as instantaneous as possible. WebRTC includes protocols like STUN and TURN that are designed to facilitate the establishment of connections when a direct connection is not possible. The typical case is a computer inside a home or o...

Troubleshooting TURN

WebRTC applications use the ICE negotiation to discovery the best way to communicate with a remote party. I t dynamically finds a pair of candidates (IP address, port and transport, also known as “transport address”) suitable for exchanging media and data. The most important aspect of this is “dynamically”: a local and a remote transport address are found based on the network conditions at the time of establishing a session. For example, a WebRTC client that normally uses a server reflexive transport address to communicate with an SFU. when running inside the home office, may use a relay transport address over TCP when running inside an office network which limits remote UDP targets. The same configuration (defined as “iceServers” when creating an RTCPeerConnection will work in both cases, producing different outcomes.

debian - Managing maintainer scripts for packages with multple .debs

If you've ever installed a package from command line on Linux, you must have noticed two main prompts related to package configuration: one asking what to do with installed configuration files with local changes, and one providing feedback right after the installation/upgrade/removal/purge has completed. Under Debian the latter was most probably the postinst script, one of the Package Maintainer Scripts which is executed after installation and configuration. These diagrams are very useful to understand what happens to the Maintainer Scripts in different circumstances: first installation, upgrade, removal, purge. Their name is probably self-explanatory: preinst , postinst , prerm , postrm . Each of them takes zero or more arguments depending on the scenario. It can help to understand that those are really just scripts executed by dpkg - and typically they are shell scripts, sometimes with interactive prompts. If you're building your own packages, you surely already h...

Giacomo Vacca

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