ec2dns

ec2dns is a set of command line tools that makes it easy to resolve public hostnames of EC2 instances and ssh into them via their tag name.

Usage of ec2dns

ec2dns provides DNS resolution of ec2 tag names under the ".ec2" TLD. If a servers tag name is appserver-1, it can be resolved as appserver-1.ec2.

ec2dns allows working with ec2 tag names like with normal domain names as shown in the following examples.

ssh

ssh ubuntu@appserver-2.ec2
ubuntu@ip-1-11-11-11:~$

scp

$ scp ubuntu@appserver-1.ec2:/etc/nginx/nginx.conf .
nginx.conf                                         100%  221     0.2KB/s   00:00

mysql

$ mysql --host=appserver-1.ec2 --user=someUser --password=somePassword someDatabase
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 348
Server version: 5.5.25a Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

ec2dns tools

ec2dns also includes wrappers around ssh and scp (if you can't or don't want to set up the DNS feature on your machine), as well as a tool to lookup hostnames and a tool to update your /etc/hosts file.

You won't need these wrapper tools if you have set up the DNS feature as shown in the installation instructions below.

ec2host

Get a list of ec2 instances

$ ec2host
i-12345678: appserver-1    ec9-99-99-99-99.compute-1.amazonaws.com
i-87654321: appserver-2    ec1-11-11-11-11.compute-1.amazonaws.com

Get the hostname of an ec2 instance by its name tag

$ ec2host appserver-1
ec9-99-99-99-99.compute-1.amazonaws.com

combine ec2host with other commands by using backticks

$ mysql --host=`ec2host appserver-1` --user=someUser --password=somePassword someDatabase
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 348
Server version: 5.5.25a Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

ec2ssh

ssh into an instance via its name tag

$ ec2ssh ubuntu@appserver-2
ubuntu@ip-1-11-11-11:~$

ssh into an instance via its name tag and execute commands

$ ec2ssh appserver-1 uptime
 13:09:10 up 1 day, 14:23,  0 users,  load average: 0.35, 0.36, 0.35

$ ec2ssh appserver-1 'uname -a'
 Linux ip-10-140-78-75 3.2.0-23-virtual #36-Ubuntu SMP Tue Apr 10 22:29:03 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

ec2scp

copy a file from an ec2 instance onto your machine

$ ec2scp ubuntu@appserver-1:/etc/nginx/nginx.conf .
nginx.conf                                         100%  221     0.2KB/s   00:00

ec2updatehostsfile

update /etc/hosts with your ec2 instances

$ sudo -E ec2updatehostsfile
Updated/Added 2 hosts.

Your machine is now able to resolve your ec2 instances by tags directly, so for example the following will just work

$ ping appserver-1

Prerequisites

• Obviously an AWS account and at least one running EC2 instance.
• Correctly set AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables.
• You need Composer to install the dependencies - you should install it globally, as described here.
• You should have a ~/bin directory and it should be included in your PATH environment variable.

Installation

Basic

• The following command installs ec2dns via Composer.

composer global require "fruux/ec2dns=~2.0.0"

• Make sure you have ~/.composer/vendor/bin/ in your path.

DNS feature

These instructions are for OS X.

• Add the configuration for the DNS resolver by creating the file /etc/resolver/ec2 and pasting the following content.

nameserver 127.0.0.1
port 57005

• Create the LaunchAgent configuration that starts the DNS server by creating the file ~/Library/LaunchAgents/com.fruux.ec2dns.plist with the following command. If you are using ZSH, you'll have to change /bin/bash to /bin/zsh.

tee ~/Library/LaunchAgents/com.fruux.ec2dns.plist <<EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
	<dict>
		<key>Label</key>
		<string>com.fruux.ec2dns</string>
		<key>ProgramArguments</key>
		<array>
			<string>/bin/bash</string>
			<string>-i</string>
			<string>-l</string>
			<string>-c</string>
			<string>$HOME/.composer/vendor/bin/ec2dns</string>
		</array>
		<key>RunAtLoad</key>
		<true/>
		<key>StandardErrorPath</key>
		<string>/usr/local/var/log/ec2dns.log</string>
		<key>StandardOutPath</key>
		<string>/usr/local/var/log/ec2dns.log</string>
	</dict>
</plist>
EOF

• Finally activate the LaunchAgent config by pasting the following into the terminal.

launchctl load ~/Library/LaunchAgents/com.fruux.ec2dns.plist

Updating

composer global update fruux/ec2dns

launchctl unload ~/Library/LaunchAgents/com.fruux.ec2dns.plist
launchctl load ~/Library/LaunchAgents/com.fruux.ec2dns.plist

Contributing

Please submit all pull requests against the master branch. Code accompanied with phpunit tests is highly appreciated. Thanks!

Acknowledgements

ec2dns is inspired by ec2-ssh and powered by aws/aws-sdk-php.

Copyright and license

Copyright (c) fruux GmbH. All rights reserved.

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Check the license.