Firecracker
Open-source virtual machine monitor from AWS for running lightweight, secure microVMs on Linux.
HN commenters like Firecracker for VM-level isolation123 in self-hosted CI runners and AI agent sandboxes,4567 and several call it easy to work with.89 The most common caveat is that it is harder to set up and operate than containers,1011 especially alongside Kubernetes.12
Why people recommend it
Agent sandboxes · 3
Commenters recommend it or build on it to isolate AI agents, and note that sandbox providers such as E2B use it.
“Firecracker VMs + support for "forking" the box were our key requirements.”
“use proper VMs like Kata Containers and Firecrackers.”
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“they use firecracker with memory in git”
CI runners · 3
Teams run CI jobs in Firecracker VMs and say microVMs make hosting runners much easier.
“It really can’t be understated how much easier hosting CI is with microvms as the security boundary.”
“We've created a Firecracker-based runner, which will run CI jobs in Firecracker VMs.”
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Strong isolation · 3
Commenters say it provides real VM isolation that is more secure than container-based options.
“we use Firecracker for the actual runners. It is provides nice isolation and it is very easy to work with.”
“first with Firecracker microVM”
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“Firecracker and gvisor are nice systems not horrible to use”
Docker replacement · 2
Some teams chose Firecracker over Docker, and one ML engineer wished they had switched sooner.
“I should have switched to running docker containers in Firecracker looooong ago.”
“We were thinking about using Docker and eventually settled on Firecracker.”
Easy to use · 2
Some users describe it as nice and very easy to work with.
“we use Firecracker for the actual runners. It is provides nice isolation and it is very easy to work with.”
“Firecracker and gvisor are nice systems not horrible to use”
Snapshots and forking · 2
Commenters use VM snapshotting and cloning for fast startup and for forking full machines.
“first with Firecracker microVM”
“Firecracker VMs + support for "forking" the box were our key requirements.”
Caveats and dissent
Complex operations · 2
Commenters say the microVM route is more complicated and harder to operate than containers.
“first with Firecracker microVM”
“For hardware virtualized machines it much harder but you can do it via:”
Kubernetes integration · 1
One user found configuring it with k3s painful.
“It really can’t be understated how much easier hosting CI is with microvms as the security boundary.”
Linux only · 1
It is described as a Linux-only choice, with other tools suggested for cross-platform needs.
“the typical choices are firecracker-based solutions”
Bare-bones · 1
One commenter describes another project as a more batteries-included alternative to it.
“batteries included alternative to firecracker”
Often compared with
1 moved from Firecracker to gVisor
2 moved from Docker to FirecrackerUnikraft2 comments mention both
1 moved from Unikraft to FirecrackerKata Containers4 comments mention both
Who recommends it in their own words
Threads where it came up
- Ask HN: What is the best microVMs for AI agents? 3 mentions
- Ask HN: Alternatives to GitHub 2 mentions
- Surprise Pay $1000 2 mentions
- Linux containers in 500 lines of code (2016) 1 mention
- The VMs Powering Mobile Agents (Instinct, Claude Code) 1 mention
- Choose Boring Technology (2015) 1 mention
Data: firecracker.json. Quotes are verbatim; the verdict and theme labels are written by a model from these comments, and every clause links to its sources.
All comments 23
“Firecracker and gvisor are nice systems not horrible to use”
“they use firecracker with memory in git”
“the typical choices are firecracker-based solutions”
“It really can’t be understated how much easier hosting CI is with microvms as the security boundary.”
“the only two options we considered viable were Firecracker and gVisor”
“batteries included alternative to firecracker”
“Firecracker VMs + support for "forking" the box were our key requirements.”
“that might be better for agent sessions: gVisor, firecracker vm”
“Do I have to go full, fat VMs or can I get by with a Firecracker-like thing?”
“we moved to a fully in-house solution with Firecracker and auto-scaling on EC2”
“we use Firecracker for the actual runners. It is provides nice isolation and it is very easy to work with.”
“a Go service that orchestrates firecracker vms”
“I should have switched to running docker containers in Firecracker looooong ago.”
“Has anyone had luck moving more things to run under gvisor or firecracker or such?”
“on top of firecracker”
“For hardware virtualized machines it much harder but you can do it via:”
“use proper VMs like Kata Containers and Firecrackers.”
“use proper VMs like Kata Containers and Firecrackers.”
“I use Kata Containers on Kubernetes (Firecrackers)”
“We've created a Firecracker-based runner, which will run CI jobs in Firecracker VMs.”
“E2b also uses firecracker.”
“We were thinking about using Docker and eventually settled on Firecracker.”
“first with Firecracker microVM”