SSH into a Docker Cloud-managed node

Estimated reading time: 2 minutes

You can use add a public SSH key to the authorized_keys file in each of your nodes so you can access Docker Cloud provisioned nodes. The quickest way to do this is to run our dockercloud/authorizedkeys) container image.

Create pair of keys

First, generate a keypair using ssh-keygen -t rsa. If you have an existing keypair you prefer to use, you can skip this step, copy the public key to your clipboard and continue on to create the authorizedkeys stack.

$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/borjaburgos/.ssh/id_rsa): dockercloud
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in dockercloud.
Your public key has been saved in dockercloud.pub.
The key fingerprint is:
ac:76:05:19:51:fa:3e:f0:c8:80:73:0d:9f:6b:b7:8f borjaburgos@MacBookPro
The key's randomart image is:
+--[ RSA 2048]----+
|        oo.      |
|         +       |
|      . +        |
|     . = +       |
|    o o S o      |
|     o + B       |
|      o * =      |
|     . o . +     |
|          E..    |
+-----------------+

Print your public key to the terminal and copy it to your clipboard.

$ more dockercloud.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC4PHh4WJqUgiWedmkIJS+L1IwxfXHkfYC0N9NZ28quXyL4zQq2CDeCQrS0RDESklnuZVCe9p5fjgEHcy+FsiTUaBbjzCndeO++gqAM6pKy4ziEY1JNpIBpbuyVIK6AJIqTWzcqprhw4G8PZetLoHug3BWiiwsIW7WHhNNsrEVEsTCnCc5vG97IHZ0A6TlP6HGvVSfCFPZiAxP48hsoEsEGjcCvY9tgJa4k60XWtHbPWtjOi90RFt9OKcbUsZa+vq/3lBG50XbMoQm3NS6A+UQQ7SKvzmwJSIYCqo5lu9UzQbVKy9o00NqXa5jkmZ9Yd0BJBjFmb3WwUR8sJWZVTPFL

Create a stack in Docker Cloud

Next, we’ll run the authorizedkeys service.

You can create a new stack in Docker Cloud and enter the following stackfile to create the service manually.

You can also click the button below to automatically create a new stack in Docker Cloud with the authorizedkeys service mostly configured. (Either way you still need to add your public key.) 

authorizedkeys:
  image: dockercloud/authorizedkeys
  deployment_strategy: every_node
  autodestroy: always
  environment:
    - AUTHORIZED_KEYS=ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC4PHh4WJqUgiWedmkIJS+L1IwxfXHkfYC0N9NZ28quXyL4zQq2CDeCQrS0RDESklnuZVCe9p5fjgEHcy+FsiTUaBbjzCndeO++gqAM6pKy4ziEY1JNpIBpbuyVIK6AJIqTWzcqprhw4G8PZetLoHaiTh343wsIW7WHhNNsrEVEsTCnCc5vG97IHZ0A6TlP6HGvVSfCFPZiAxP48hsoEsEGjcCvY9tgJa4k60XWtHbPWtjOi90RFt9OKcbUsZa+vq/3lBG50XbMoQm3NS6A+UQQ7SKvzmwJSIYCqo5lu9UzQbVKy9o00NqXa5jkmZ9Yd0BJBjFmb3WwUR8sJWZVTPFL
  volumes:
    - /root:/user:rw

Change the AUTHORIZED_KEYS value to the public key you copied to your clipboard in the previous step.

From the stack page, click Create and deploy.

The service runs, copies your public key to all of your nodes, then terminates and automatically destroys the container.

Note: the default configuration of this service copies the public key you enter to ALL of your existing nodes.

SSH into Docker Cloud node

Next, get the node’s IP from Docker Cloud from the Node details page.

With that IP number, you can then SSH to the node as root.

$ ssh -i ~/dockercloud root@104.236.69.138
The authenticity of host '104.236.69.138 (104.236.69.138)' can't be established.
RSA key fingerprint is 4b:22:71:39:53:4a:88:51:4b:a7:2e:ed:03:dd:a3:7f.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '104.236.69.138' (RSA) to the list of known hosts.
Welcome to Ubuntu 14.04.1 LTS (GNU/Linux 3.13.0-40-generic x86_64)
 * Documentation:  https://help.ubuntu.com/
  System information as of Mon Feb  2 23:29:53 EST 2015
  System load:  0.2                Users logged in:        0
  Usage of /:   16.0% of 19.56GB   IP address for eth0:    104.236.69.138
  Memory usage: 52%                IP address for eth1:    10.132.224.214
  Swap usage:   0%                 IP address for docker0: 172.17.42.1
  Processes:    111
  Graph this data and manage this system at:
    https://landscape.canonical.com/
Last login: Mon Feb  2 23:29:54 2015 from pool-108-30-19-181.nycmny.fios.verizon.net
root@13e9d739-admin:~#
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