Pin a jailer-launched Firecracker microVM to a nested cgroup v2 hierarchy
domain: firecracker-microvm.github.io · 4 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Pass --cgroup-version 2 and one or more --cgroup <file>=<value> flags, e.g. --cgroup cpuset.cpus=0 --cgroup memory.max=536870912.
With any --cgroup flag (or cgroup-version 1), the jailer creates a NEW cgroup <id> at <cgroup_base>/<parent_cgroup>/<id> and writes the process pid into its tasks file.
Use --parent-cgroup to place the VM under a custom nested hierarchy instead of the default <exec-file-name>.
After launch, verify the process is under the expected cgroup path in /sys/fs/cgroup and that the limits apply.
Known gotchas
If you specify NO --cgroup AND --cgroup-version 2, the jailer does NOT create a new cgroup: it only moves the process into the named cgroup if it already exists.
In v2, moving into a cgroup that has domain controllers enabled (e.g. memory in cgroup.subtree_control) FAILS because of the 'no internal process constraint' — the parent must have no internal processes, only child cgroups.
Under v1, the jailer parses /proc/mounts to find controller mount locations itself.
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