Consistent security controls and high reliability are common expectations for any systems administrator. How do you deliver both on a network with thousands of servers supporting thousands of engineers? Most off-the-shelf solutions require a compromise in at least one of these areas — and we refused to accept this.

Most systems administrators use the industry-standard Secure Shell (SSH) for accessing systems, and yet many of its special features are not widely leveraged. At Facebook, we take advantage of those features to use SSH in a way that is reliable, secure, and manageable. SSH, more specifically OpenSSH, has a great way to provide both the security and reliability we require: signed certificates with principals.