mock-ec2-metadata

A simple service (written in go using gizmo) to mock the ec2 metadata service. This is usefully for development images (like vagrant or packer) that require Instance base IAM permission or other metadata information.

For example, cob and s3-iam can both use s3 as a yum repo. Both of these systems rely on the instances the proper credentials to have authorization to the s3 repos that yum uses.

The metadata service normal listens on a special private ip address 169.254.169.254. This is a special address that will not exist on your system. One option is to bind an alias to the loopback iterface. This can be done with the following command:

/sbin/ifconfig lo:1 inet 169.254.169.254 netmask 255.255.255.255 up

Many services assume that use the metadata service uses a default port 80 and do not allow configuration or override. A simple IP talbes rule and IP forwarding can get around that, as follows:

$ echo 1 > /proc/sys/net/ipv4/ip_forward
$ iptables -t nat -A OUTPUT -p tcp -d 169.254.169.254/32 --dport 80  -j DNAT --to-destination 169.254.169.254:8111
$ service iptables save

Configuration

All configuration is contained in either ./mock-ec2-metadata-config.json or /etc/mock-ec2-metadata-config.json, the former overriding the latter.

Currently the support URLs for the metadata service are:

• http://169.254.169.254/latest/meta-data/
• http://169.254.169.254/latest/meta-data/ami-id
• http://169.254.169.254/latest/meta-data/ami-launch-index
• http://169.254.169.254/latest/meta-data/ami-manifest-path
• http://169.254.169.254/latest/meta-data/placement/availability-zone
• http://169.254.169.254/latest/meta-data/hostname
• http://169.254.169.254/latest/meta-data/instance-action
• http://169.254.169.254/latest/meta-data/instance-id
• http://169.254.169.254/latest/meta-data/instance-type
• http://169.254.169.254/latest/meta-data/local-hostname
• http://169.254.169.254/latest/meta-data/local-ipv4
• http://169.254.169.254/latest/meta-data/mac
• http://169.254.169.254/latest/meta-data/profile
• http://169.254.169.254/latest/meta-data/reservation-id
• http://169.254.169.254/latest/meta-data/security-groups
• http://169.254.169.254/latest/meta-data/iam/security-credentials

Getting started

This project requires Go to be installed. On OS X with Homebrew you can just run brew install go.

Running it then should be as simple as:

$ make deps
$ make
$ ./bin/mock-ec2-metadata

Testing

make test

License

See LICENSE

Contributing

See CONTRIBUTING.md for more details.