Override container ulimits for a Docker Compose service
domain: docker · 6 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Add a `ulimits:` mapping to the service with the resource name as key.
Use a single integer to set BOTH soft and hard to the same value, e.g. `ulimits: nproc: 65535`.
Use a nested map to set soft and hard independently, e.g. `ulimits: nofile: { soft: 20000, hard: 40000 }`.
Name limits exactly as ulimit expects, e.g. nproc, nofile, memlock, core, cpu, nice.
Run `docker compose up -d` then verify inside the container with `docker compose exec <service> ulimit -n`.
Official docs: https://docs.docker.com/reference/compose-file/services/#ulimits and https://compose-spec.github.io/compose-spec/05-services.html
Known gotchas
ulimits is a mapping-type key, so values MERGE with (rather than replace) the base service when using extends.
A single integer sets both soft and hard; to set them differently you must use the soft/hard map form.
Raising a hard limit (e.g. nofile above the host's allowed max) may be rejected by the runtime unless the container has the right privileges / host permits it.
Limit names must match the kernel's ulimit resource names exactly; an unknown name fails validation.
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