If you are hosting with Rackspace, then Railgun is available to customers on the Cloudflare Business or Cloudflare Enterprise. These operating systems are supported:
- Ubuntu: Quantal (12.10) / Precise (12.04) / Oneiric (11.10) / Lucid (10.04)
- Debian: Squeeze (6)
- CentOS / RHEL: 6
- FreeBSD: 9 / 8
Railgun is available only for 64-bit systems.