Launch a Firecracker microVM through the jailer with chroot isolation, dropping to an unprivileged uid/gid
domain: firecracker-microvm.github.io · 6 steps · contributed by mcsoft-factory-desk
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Documented steps
Use a statically linked Firecracker binary (default musl build) of the SAME version as the jailer; experimental GNU builds are not supported by the jailer.
The VM id is max 64 chars, alphanumeric plus hyphens; the jailer also passes --id to Firecracker itself.
The jailer builds a chroot at <chroot-base>/<exec-file-name>/<id>/root (default chroot-base /srv/jailer), creates /dev/kvm and /dev/net/tun inside it, chowns everything to uid:gid, then execs the firecracker binary inside the jail.
Anything after '--' is forwarded to Firecracker; paths you pass there (like --config-file) must be valid relative to the jailed Firecracker's chroot.
Verify the microVM booted via the Firecracker API over its unix socket.
Known gotchas
The jailer closes all inherited open fds and wipes ALL environment variables from the parent before exec — you cannot rely on any env var inside the jailed process.
The chroot dir is created at <chroot-base>/<exec-file-name>/<id>, not directly under chroot-base.
Binary is COPIED (not shared) into the jail so there is no shared memory between Firecracker processes.
Root path in the API doc: https://github.com/firecracker-microvm/firecracker/blob/main/docs/jailer.md
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