This is a very simple alpine based SSHD server, listening on port 22. It has no fancy stuff. Just SSHD service running in foreground. It allows only key based access, and the user is root. Useful as a jump host inside kubernetes clusters, to further connect to your other secure services behind firewall, etc. You can use it for port forwarding, ssh-agent forwarding, etc.
- The user root's password is un-assigned.
- The only authentication enabled over ssh is key based authentication. Repeat: Password based authentication is disabled.
- The container expects a ENV variable named "AUTHORIZED_KEYS" containing your SSH public key in it. If this ENV var is found empty, this container does not start. This prevents it becoming an open-(ssh)-relay.
So simply pass your ssh public key as env var AUTHORIZED_KEYS to the container at run time, and you are good to go. You can actually pass multiple SSH public keys by putting them in one file, and then letting the entire file load as a string in this ENV variable. For example:
AUTHORIZED_KEYS="$(cat .ssh/my_many_ssh_public_keys_in_one_file.txt)"
(key is truncated for convenience, of-course)
[kamran@kworkhorse alpine-sshd]$ AUTHORIZED_KEYS="ssh-rsa AAAAB3NzaC1yc2JADfoDX5w== [email protected]"
[kamran@kworkhorse alpine-sshd]$ docker run -e AUTHORIZED_KEYS="${AUTHORIZED_KEYS}" -d praqma/alpine-sshd
a85de77b70a195531570ac45e63a94dd270ad1dd917f3f470daeb9f6a88e2daf
[kamran@kworkhorse alpine-sshd]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a85de77b70a1 praqma/alpine-sshd "/docker-entrypoint.…" 2 seconds ago Up 2 seconds relaxed_fermi
[kamran@kworkhorse alpine-sshd]$
[kamran@kworkhorse alpine-sshd]$ docker inspect relaxed_fermi | grep -w IPAddress
"IPAddress": "172.17.0.2",
"IPAddress": "172.17.0.2",
Now access this container using ssh:
[kamran@kworkhorse alpine-sshd]$ ssh [email protected]
Welcome to Alpine!
The Alpine Wiki contains a large amount of how-to guides and general
information about administrating Alpine systems.
See <http://wiki.alpinelinux.org>.
You can setup the system with the command: setup-alpine
You may change this message by editing /etc/motd.
a85de77b70a1:~#
[kamran@kworkhorse alpine-sshd]$ docker run -d praqma/alpine-sshd
32cf51a135275f76f2c1866dbf3c36ee1891b3644b0c2bfa24af510e506e4f24
[kamran@kworkhorse alpine-sshd]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
[kamran@kworkhorse alpine-sshd]$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
32cf51a13527 praqma/alpine-sshd "/docker-entrypoint.…" 9 seconds ago Exited (1) 8 seconds ago fervent_galileo
[kamran@kworkhorse alpine-sshd]$ docker logs fervent_galileo
Need your ssh public key as AUTHORIZED_KEYS env variable. Abnormal exit ...
[kamran@kworkhorse alpine-sshd]$
[kamran@kworkhorse alpine-sshd]$ docker run -e AUTHORIZED_KEYS="some random string" -d test/alpine-sshd
f240cea71d36fec8d0a556b97d488ceaf53bcd781d36111695a3225471e6b02f
[kamran@kworkhorse alpine-sshd]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f240cea71d36 test/alpine-sshd "/docker-entrypoint.…" 4 seconds ago Up 4 seconds 22/tcp hungry_murdock
[kamran@kworkhorse alpine-sshd]$ ssh [email protected]
[email protected]: Permission denied (publickey,keyboard-interactive).
[kamran@kworkhorse alpine-sshd]$
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