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AWS accounts

SSH into AWS machines

This document explains how to SSH into machines in AWS, and what commands exist to navigate machines and applications quickly.

Visualisation of commands from dev to production machine

In AWS, there are no static hostnames, so we can’t have backend-1.backend.integration to SSH to like in Carrenza. EC2 instances have dynamically assigned IPs, which means hostnames like ip-10-1-5-53.eu-west-1.compute.internal. Each Puppeted instance has a “node class” (backend, frontend, …) and the list of instances belonging to these classes is accessible via govuk_node_list when logged onto the environment.

To help connecting to the environments, there is a wrapper tool called govukcli. The tool uses the idea of “contexts”, where a “context” is a specific environment. By setting a context, any subsequent govukcli commands will be tied to the environment you chose.

Setup

Clone the govuk-aws repository and add a symlink to make govukcli executable globally:

cd ~/govuk
git clone https://github.com/alphagov/govuk-aws
ln -s ~/govuk/govuk-aws/tools/govukcli /usr/local/bin/govukcli

You will also need to have followed the Get SSH access to integration instructions.

Usage

Local dev machine

To view all possible contexts, run:

local$ govukcli list-contexts

To set a persistent context:

local$ govukcli set-context integration

Now when you SSH into an instance, it will be to one running on the specified environment:

# SSH into a 'calculators_frontend' node in current context (Integration)
local$ govukcli ssh calculators_frontend

Alternatively, you can set a context for the current command only by passing a CLI parameter:

# SSH into a 'calculators_frontend' node in Staging, ignoring local context
local$ govukcli ssh --context staging calculators_frontend

Note that the SSH examples above will SSH you into a random machine of the right node class. You can find out which class you need by finding the corresponding app page.

govukcli finds a matching machine via the ‘jumpbox’, which you can also SSH into directly:

local$ govukcli ssh jumpbox

Jumpbox

The jumpbox is a special node that knows about all of the other nodes in its environment.

List the IP addresses of every node in the environment:

jumpbox$ govuk_node_list

This long list of IPs is not very useful on its own, but you can filter it by node class:

jumpbox$ govuk_node_list -c backend

And if you can’t remember the names of the node classes, there’s a built-in helper:

jumpbox$ govuk_node_list --classes

Once you have found the IP of the machine you want to SSH into, you can manually SSH directly from the jumpbox machine:

jumpbox$ ssh ip-10-1-5-22.eu-west-1.compute.internal

You can also do this from your local machine by appending the environment to the address:

local$ ssh ip-10-1-5-22.eu-west-1.compute.internal.integration

Note that in Carrenza, there are no dynamic IPs, so you can SSH into a specific node by name. There are no Carrenza machines on Integration anymore, so these examples assume you’ve set context to staging:

# SSH into the `backend-1.backend.staging` node
local$ govukcli ssh backend-1

…or as with AWS, you can SSH into a random machine of the right node class:

# This may SSH into `backend-1.backend.staging` or into a different node
local$ govukcli ssh backend

Application node

Now you’re on the node running the application you want to explore. There are two main ways of interacting with the running application.

You can start up an application console (typically Rails):

node$ govuk_app_console

…or you can start up a database console (typically PostgreSQL):

node$ govuk_app_dbconsole

These common commands, along with govuk_node_list, live in govuk-puppet.

Troubleshooting

Sometimes you might try to ssh into a server and nothing happens. Double-check that you have added the key into the keychain like so: ssh-add -K ~/.ssh/id_rsa.

Make sure you have been granted access. For example, if you have yet to be granted access to production, your attempt to SSH into a production node will fail silently.

If in doubt, run GOVUKCLI_OUTPUT=debug govukcli ssh backend to help you to debug.

This page was last reviewed on 12 July 2019. It needs to be reviewed again on 12 January 2020 by the page owner #govuk-2ndline .
This page was set to be reviewed before 12 January 2020 by the page owner #govuk-2ndline. This might mean the content is out of date.