Fly (by superfly)

Init-snapshot Alternatives

Similar projects and alternatives to init-snapshot

NOTE: The number of mentions on this list indicates mentions on common posts plus user suggested alternatives. Hence, a higher number means a better init-snapshot alternative or higher similarity.

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init-snapshot reviews and mentions

Posts with mentions or reviews of init-snapshot. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2023-02-27.
  • Firecracker internals: deep dive inside the technology powering AWS Lambda(2021)
    9 projects | | 27 Feb 2023
    At CodeSandbox we use Firecracker to run our VMs (more info here:

    To answer the questions:

    > what version of the kernel do you use (the github page says 5.10 but isn't that quite old?)

    Right, they have tested with 5.10, but it also works with higher kernel versions. Our host currently runs 5.19 and we're planning to upgrade to 6.1 soon. The guest runs 5.15.63, we use a config very similar to the recommended config by FC team (it's in the FC repo). It's important to mention that we had to disable async pagefaulting (a KVM feature) with more modern kernel versions, as VMs could get stuck waiting for an PF resolve.

    > What do you use to build the 'micro' images

    We created a CLI that creates a rootfs from a Docker image. It pulls the image, creates a container and then extracts the fs from it to an ext4 disk. For the init, we forked the open sourced init from the Fly team ( and changed/added some functionality.

    > How do you keep timesync of you're not using a timesync daemon?

    IIRC we expose the time as a PTP device (handled by kvm) and run phc2sys to sync the time in an interval. Firecracker has some documentation on this, where it recommends chrony. It can also be done with vsock, but it would be more manual.

    > Handle kernel and app logs without adding an log daemon, and same through vsocks, etc?

    The init forwards stdout/stderr of the command it runs to its own stdout, which Firecracker then logs out by itself. A supervisor reads these and writes the logs to files.

  • The Reclaimer of Heroku's Magic
    5 projects | | 15 May 2022
    Unless they’ve changed things, there is no containerization within the VM a la kata. They run their own custom init inside the VM and use it to start the entry point. is the source.
  • Docker without Docker
    5 projects | | 2 Jun 2021
    Jerome wrote our init in Rust, and, after being cajoled by Josh Triplett, [we released the code (, which you can go read.
  • Fly’s Prometheus Metrics
    1 project | | 13 May 2021
    > transforms container images into fleets of micro-VMs running around the world on our hardware.

    Oh boy!

    > None of us have ever worked for Google, let alone as SREs. So we’re going out on a limb

    Oh.... boy.

    > We spent some time scaling it with Thanos, and Thanos was a lot, as far as ops hassle goes.

    You know, they have these companies now, that will collect your metrics for you, so that you don't have to deal with ops hassle.

    Holy shit. I see they even wrote their own init... in Rust. Yes, the thing that is normally a shell script, is now a compiled program in a new language, that mostly just runs mkdir(), mount() and ethtool(). (

  • Rust-based init for virtual machines
    1 project | | 17 Feb 2021
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