Notes
This repo has been archived, follow up project at https://github.com/alpine-docker/multi-arch-libs/tree/master/socat
socat
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Run socat command in alpine container
Weekly auto-trigger docker build for socat when new version is released.
New features: support multi-arch now.
Repo:
https://github.com/alpine-docker/socat
Daily build logs:
https://app.circleci.com/pipelines/github/alpine-docker/socat
Docker image tags:
https://hub.docker.com/r/alpine/socat/tags/
Use Case: Expose a tcp socket for accessing docker API on macOS
The Docker for Mac native macOS application provides use of docker engine without the need for vagrant or other virtualized linux operating system. Docker for Mac does not provide the same docker daemon configuration options as other versions of docker-engine. macOS-socat uses socat to establish a tcp socket bound to localhost which makes available the Docker for Mac API.
Example
To publish the unix-socket (/var/run/docker.sock) to the Docker daemon as port 2376 on the local host (127.0.0.1):
$ docker pull alpine/socat
$ docker run -d --restart=always \
-p 127.0.0.1:2376:2375 \
-v /var/run/docker.sock:/var/run/docker.sock \
alpine/socat \
tcp-listen:2375,fork,reuseaddr,ignoreeof unix-connect:/var/run/docker.sock
WARNING: The Docker API is insecure by default. Please remember to bind the TCP socket to the localhost
interface otherwise the Docker API will be bound to all interfaces.
Use Case: Publish a port on an existing container
Docker does not allow easy publishing of ports on existing containers. Changing published ports is done by destroying existing containers and creating them with changed options. Alternative solutions require firewall access, and are vulnerable to changes in the addresses of said containers between restarts.
This image can be used to work-around these limitations by forwarding ports and linking containers
Example
To publish port 1234 on container example-container as port 4321 on the docker host:
$ docker pull alpine/socat
$ docker run \
--publish 4321:1234 \
--link example-container:target \
alpine/socat \
tcp-listen:1234,fork,reuseaddr tcp-connect:target:1234
- To run the container in the background insert
--detach
afterdocker run
. - To automatically start the container on restart insert
--restart always
afterdocker run
. - To automatically start the container unless it has been stopped explicitly insert
--restart unless-stopped
afterdocker run
.
Use Case: Use nginx-proxy to access a local Cockpit instance
Socat docker image by defintion does not use any EXPOSE inside Dockerfile. This may prejudice other containers that rely on this information, like nginx-proxy (https://github.com/nginx-proxy/nginx-proxy).
Using expose will allow nginx-proxy to properly detect and communicate with socat instance without opening the port on host like ports option does.
Example
In the following example, socat will be used to relay a host Cockpit instance to the nginx-proxy image, allowing to rely on proxy ports and optional Let's Encrypt support.
cockpit-relay:
image: alpine/socat
container_name: cockpit-relay
depends_on:
- nginx-proxy
command: "TCP-LISTEN:9090,fork,reuseaddr TCP:172.17.0.1:9090"
expose:
- "9090"
environment:
- VIRTUAL_HOST=somehost.somedomain
- VIRTUAL_PROTO=https
- LETSENCRYPT_HOST=somehost.somedomain
- [email protected]
restart: unless-stopped
logging:
driver: journald
networks:
- webservices
The Processes to build this image
- Enable CI cronjob on this repo to run build daily on master branch
- Build the image locally, and get its latest version
- Match the exist docker image tags via Hub.docker.io REST API
- If not matched, build the image with latest version as tag and push to hub.docker.com
- Docker tags as socat's version, such as 1.7.3.3-rc0, are built by ci auto-trigger cron jobs.