Make your OpenSSH fly on Alpine

Overview

Use this Dockerfile / -image to start a slim and highly customizable sshd-server with bash and rsync installed.

Regular builds, automagically

Thanks to Travis-CI this image is pushed weekly and creates new tags if there are new versions available.

Tags

For recent tags check Dockerhub.

Features

• bash-shell and rsync installed
• Default .bashrc from ubuntu
• Desired shell is configurable by --env
• En- or disable root-user by --env
  • Choose between keypar and password auth for root
  • Password for root is configurable by --env
• Additional ssh-users can be created by --env
  • Authentication for additional users is done by keypair
• Beautifully colored log output

Usage examples

Authentication as root by password

$ docker run --rm \
--publish=1337:22 \
--env ROOT_PASSWORD=MyRootPW123 \
hermsi/alpine-sshd

After the container is up you are able to ssh in it as root with the in --env provided password for "root"-user.

$ ssh root@mydomain.tld -p 1337

Authentication as root by ssh-keypair

$ docker run --rm \
--publish=1337:22 \
--env ROOT_KEYPAIR_LOGIN_ENABLED=true \
--volume /path/to/authorized_keys:/root/.ssh/authorized_keys \
hermsi/alpine-sshd

After the container is up you are able to ssh in it as root with a private-key which matches the provided public-key in authorized_keys for "root"-user.

$ ssh root@mydomain.tld -p 1337 -i /path/to/private_key

Authenticate as additional user by ssh-keypair

$ docker run --rm \
--publish=1337:22 \
--env SSH_USERS="hermsi:1000:1000" \
--volume /path/to/hermsi_public_key:/conf.d/authorized_keys/hermsi \
hermsi/alpine-sshd

After the container is up you are able to ssh in it as the given user with a private-key that matches the provided public-key in authorized_keys for your created user.

$ ssh mydomain.tld -l hermsi -p 1337 -i /path/to/hermsi_private_key

Create multiple, additional users with keypair

$ docker run --rm \
--publish=1337:22 \
--env SSH_USERS="hermsi:1000:1000,dennis:1001:1001" \
--volume /path/to/hermsi_public_key:/conf.d/authorized_keys/hermsi \
--volume /path/to/dennis_public_key:/conf.d/authorized_keys/dennis \
hermsi/alpine-sshd

After the container is up you are able to ssh in it as one of the given users with a private-key that matches the provided public-key in authorized_keys for your desired user.

$ ssh root@mydomain.tld -p 1337 -i /path/to/private_key

Configuration

While beeing very slim and vanilla this image is still highly customizable.

Environment variables

Variable	Possible Values	Default value	Explanation
ROOT_LOGIN_UNLOCKED	'true' or 'false'	'false'	Whether to enable or disable login as 'root' user
ROOT_KEYPAIR_LOGIN_ENABLED	'true' or 'false'	'false'	Enable login as 'root' by keypair (implies ROOT_LOGIN_UNLOCKED). Must mount public-key into container: /root/.ssh/authorized_keys
ROOT_PASSWORD	any desired string	undefined	Set password for login as root (implies ROOT_LOGIN_UNLOCKED)
USER_LOGIN_SHELL	any existing shell	/bin/bash	Choose the desired default shell for all additional users. If the configured shell is not existent, a fallback to /bin/ash is applied

Extending this image

This image is designed to be as slim and vanilla as possible.
If you need additional Tools like git , I definetly recommend to build your own image on top of alpine-sshd:

FROM  hermsi/alpine-sshd:latest

RUN   apk add --no-cache \
            git

Use with docker-compose

I built this image in order to use it along with a nginx and fpm-php container for transferring files via sftp. If you are interested in a Dockerfile which fulfills this need: this way