Firecracker v0.21.0

Added

• Support for booting with an initial RAM disk image. This image can be
  specified through the new initrd_path field of the /boot-source API
  request.

Fixed

• Fixed #1469 - Broken GitHub location for Firecracker release binary.
• The jailer allows changing the default api socket path by using the extra
  arguments passed to firecracker.
• Fixed #1456 - Occasional KVM_EXIT_SHUTDOWN and bad syscall (14) during
  VM shutdown.
• Updated the production host setup guide with steps for addressing
  CVE-2019-18960.
• The HTTP header parsing is now case insensitive.
• The put_api_requests and patch_api_requests metrics for net devices were
  un-swapped.

Changed

• Removed redundant --seccomp-level jailer parameter since it can be
  simply forwarded to the Firecracker executable using "end of command
  options" convention.
• Removed memory.dirty_pages metric.
• Removed options field from the logger configuration.
• Decreased release binary size by ~15%.
• Changed default API socket path to /run/firecracker.socket. This path
  also applies when running with the jailer.
• Disabled KVM dirty page tracking by default.
• Removed redundant RescanBlockDevice action from the /actions API.
  The functionality is available through the PATCH /drives API.
  See docs/api_requests/patch-block.md.