Firecracker is an open source Virtual Machine Monitor (VMM) that enables secure, multi-tenant, minimal-overhead execution of container and function workloads.
Firecracker was built by developers at Amazon Web Services to enable services such as AWS Lambda and AWS Fargate to improve resource utilization and customer experience, while providing the security and isolation required of public cloud infrastructure. Firecracker started from Chromium OS's Virtual Machine Monitor, crosvm, an open source VMM written in Rust. Today, crosvm and Firecracker have diverged to serve very different customer needs. Rust-vmm is an open source community where we collaborate with the crosvm maintainers and other groups and individuals to build and share quality Rust virtualization components.
When we launched Lambda in November of 2014, we were focused on providing a secure serverless experience. At launch we used per-customer EC2 instances to provide strong security and isolation between customers. As Lambda grew, we saw the need for technology to provide a highly secure, flexible, and efficient runtime environment for services like Lambda and Fargate. Using our experience building isolated EC2 instances with hardware virtualization technology, we started an effort to build a VMM that was tailored to integrate with container ecosystems.
The Firecracker VMM is built to be processor agnostic. Intel processors are supported for production workloads. Support for AMD and Arm processors is in developer preview.
Yes. Firecracker is integrated with Kata Containers, Weave FireKube (via Weave Ignite), and containerd via firecracker-containerd. We welcome contributions that enable Firecracker to integrate naturally with the container ecosystem and provide more choices in how container workloads are isolated.
Firecracker is an alternative to QEMU that is purpose-built for running serverless functions and containers safely and efficiently, and nothing more. Firecracker is written in Rust, provides a minimal required device model to the guest operating system while excluding non-essential functionality (only 5 emulated devices are available: virtio-net, virtio-block, virtio-vsock, serial console, and a minimal keyboard controller used only to stop the microVM). This, along with a streamlined kernel loading process enables a < 125 ms startup time and a < 5 MiB memory footprint. The Firecracker process also provides a RESTful control API, handles resource rate limiting for microVMs, and provides a microVM metadata service to enable the sharing of configuration data between the host and guest.
Firecracker supports Linux host and guest operating systems with kernel versions 4.14 and above, as well as OSv guests. The long-term support plan is still under discussion.
Firecracker is licensed under the Apache License, version 2.0, allowing you to freely use, copy, and distribute your changes under the terms of your choice. Read more about Apache 2.0. Crosvm code sections are licensed under a BSD-3-Clause license that also allows you to use, copy, and distribute your changes under the terms of your choice.
Firecracker is an AWS open source project that encourages contributions from customers and the developer community. Any contribution is welcome as long as it aligns with our charter. You can learn more about how to contribute in CONTRIBUTING.md. You can chat with others in the community on the Firecracker Slack workspace.
The Firecracker team at Amazon Web Services owns project maintainer responsibilities, permissions to merge pull requests, and the ability to create new Firecracker releases.
Initrds are only recently supported in Firecracker. If your release predates issue #228 being resolved, please update.
In order to debug the issue, check the response of the InstanceStart API
request. Possible responses:
- Error: Submit a new issue with the label "Support: Failure".
- Success: If the boot was successful, you should get a response with 204 as the status code.
If you have no output in the console, most likely you will have to update the kernel command line. By default, Firecracker starts with the serial console disabled for boot time performance reasons.
Example of a kernel valid command
line that enables the serial console (which goes in the boot_args field of
the /boot-source Firecracker API resource):
console=ttyS0 reboot=k panic=1 pci=off nomodules
The ip= boot param in the linux kernel only actually supports configuring a
single interface. Multiple interfaces can be set up in Firecracker using the
API, but guest IP configuration at boot time through boot arguments can only be
done for a single interface.
The canonical solution is to use NTP in your guests.
However, if you want to run Firecracker at scale, we suggest using a PTP emulated device as the guest's NTP time source so as to minimize network traffic and resource overhead. With this solution the guests will constantly update time to stay in sync with host wall-clock. They do so using cheap para-virtualized calls into kvm ptp instead of actual network NTP traffic.
To be able to do this you need to have a guest kernel compiled with KVM_PTP
support:
CONFIG_PTP_1588_CLOCK=y
CONFIG_PTP_1588_CLOCK_KVM=y
Our recommended guest kernel config already has these included.
Now /dev/ptp0 should be available in the guest. Next you need to configure
/dev/ptp0 as a NTP time source.
For example when using chrony:
- Add
refclock PHC /dev/ptp0 poll 3 dpoll -2 offset 0to the chrony conf file (/etc/chrony/chrony.conf) - Restart the
chronydaemon.
You can see more info about the refclock parameters
here.
Adjust them according to your needs.
The relatively high FD usage is expected and correct. Firecracker heavily relies on event file descriptors to drive device emulation.
There is no relation between the numbering of the /network-interface API calls
and the number of the network interface in the guest. Rather, it is usually
the order of network interface creation that determines the number in the guest
(but this depends on the distribution).
For example, when you create two network interfaces by calling
/network-interfaces/1 and then /network-interfaces/0, it may result in this
mapping:
/network-interfaces/1 -> eth0
/network-interfaces/0 -> eth1
Firecracker does not implement ACPI and PM devices, therefore operations like gracefully rebooting or powering off the guest are supported in unconventional ways.
Running the poweroff or halt commands inside a Linux guest will bring it down but
Firecracker process remains unaware of the guest shutdown so it lives on.
Running the reboot command in a Linux guest will gracefully bring down the guest
system and also bring a graceful end to the Firecracker process.
Issuing a SendCtrlAltDel action command through the Firecracker API will generate a
Ctrl + Alt + Del keyboard event in the guest resulting in a clean reboot on most
guest Linux systems.
Check out our rootfs and kernel image creation guide.
If you see errors like ...
[<TIMESTAMP>] fc_vmm: page allocation failure: order:6, mode:0x140c0c0
(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null)
[<TIMESTAMP>] fc_vmm cpuset=<GUID> mems_allowed=0
... then your host is running out of memory. KVM is attempting to do an
allocation of 2^order bytes (in this case, 6) and there aren't sufficient
contiguous pages.
Possible mitigations are:
- Track the failing allocations in the
dmesgoutput and rebuild the host kernel so as to usevmallocinstead ofkmallocfor them. - Reduce memory pressure on the host.
Passing an optional command line parameter, --config-file, to the Firecracker
process allows this type of configuration. This parameter must be the path to a
file that contains the JSON specification that will be used to configure and start
the microVM. One example of such file can be found at tests/framework/vm_config.json.
If the Firecracker process exits with 12 exit code (Out of memory error), the root
cause is that there is not enough memory on the host to be used by the Firecracker microVM.
If the microVM was not configured in terms of memory size through an API request, the host needs to meet the minimum requirement in terms of free memory size, namely 128 MB of free memory which the microVM defaults to.
If another hypervisor like VMware or VirtualBox is running on the host and locks /dev/kvm,
Firecracker process will fail to start with "Resource busy" error.
This issue can be resolved by terminating the other hypervisor running on the host, and allowing Firecracker to start.