## `ssh-agent` support for user keys

You can now use `ssh-agent` to hold your user key when using knife. This allows storing your user key in an encrypted form as well as using `ssh -A` agent forwarding for running knife commands from remote devices.

You can enable this by adding `ssh_agent_signing true` to your `knife.rb` or `ssh_agent_signing = true` in your `credentials` file.

To encrypt your existing user key, you can use OpenSSL:

```bash
( openssl rsa -in user.pem -pubout && openssl rsa -in user.pem -aes256 ) > user_enc.pem
chmod 600 user_enc.pem
```

This will prompt you for a passphrase for to use to encrypt the key. You can then load the key into your `ssh-agent` by running `ssh-add user_enc.pem`. Make sure you add the `ssh_agent_signing` to your configuration, and update your `client_key` to point at the new, encrypted key (and once you've verified things are working, remember to delete your unencrypted key file).

## default_env Property in Execute Resource

The shell_out helper has been extended with a new option `default_env` to allow disabling Chef from modifying PATH and LOCALE environmental variables as it shells out. This new option defaults to true (modify the env), preserving the previous behavior of the helper.

The execute resource has also been updated with a new property `default_env` that allows utilizing this the ENV sanity functionality in shell_out. The new property defaults to false, but it can be set to true in order to ensure a sane PATH and LOCALE when shelling out. If you find that binaries cannot be found when using the execute resource, `default_env` set to true may resolve those issues.

## Small Size on Disk

Chef now bundles the inspec-core and train-core gems, which omit many cloud dependencies not needed within the Chef client. This change reduces the install size of a typical system by ~22% and the number of files within that installation by ~20% compared to Chef Infra Client 14.1. Enjoy the extra disk space.

## Virtualization detection on AWS

Ohai now detects the virtualization hypervisor `amazonec2` when running on Amazon's new C5/M5 instances.