[2014-09-04T01:17:24+09:00] WARN:
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SSL validation of HTTPS requests is disabled. HTTPS connections are still
encrypted, but chef is not able to detect forged replies or man in the middle
attacks.

To fix this issue add an entry like this to your configuration file:

```
  # Verify all HTTPS connections (recommended)
  ssl_verify_mode :verify_peer

  # OR, Verify only connections to chef-server
  verify_api_cert true
```

To check your SSL configuration, or troubleshoot errors, you can use the
`knife ssl check` command like so:

```
  knife ssl check -c /home/chefsolo/chef-solo/solo.rb
```

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対処法

knife-soloの最新版を使う

設定ファイルをいじる

ssl_verify_mode  :verify_peer

参考