crun

fast OCI container runtime

TLDR

Run a container from OCI bundle

$ crun run [container_id]

Create a container without starting it

$ crun create [container_id]

Start a created container

$ crun start [container_id]

List running containers

$ crun list

Execute a command in a running container

$ crun exec [container_id] [command]

Delete a container

$ crun delete [container_id]

Get container state

$ crun state [container_id]

Pause all processes in a container

$ crun pause [container_id]

Show processes running in a container

$ crun ps [container_id]

SYNOPSIS

crun [global-options] command [command-options] [arguments]

crun is a fast and low-memory footprint OCI container runtime written in C. It is fully compatible with the OCI (Open Container Initiative) runtime specification and can be used as a drop-in replacement for runc.crun implements all required OCI runtime operations including container creation, execution, and lifecycle management. It supports Linux namespaces, cgroups v1 and v2, seccomp, and other container isolation features.The runtime is designed to be lightweight and efficient, with significantly faster startup times and lower memory usage compared to Go-based runtimes. It's used by container engines like Podman and Buildah.

PARAMETERS

run ID

Create and start a container from an OCI bundle.

create ID

Create a container but don't start it.

start ID

Start a previously created container.

exec ID CMD

Execute a command in a running container.

delete ID

Delete a container.

kill ID [SIGNAL]

Send a signal to the container's init process.

list

List containers.

state ID

Output the state of a container.

pause ID

Pause all processes in the container.

resume ID

Resume the processes in the container.

ps ID

Show the processes running in a container.

update ID

Update container resource constraints.

spec

Create a new OCI bundle specification.

checkpoint ID

Checkpoint a running container using CRIU.

--root DIR

Root directory for container state.

--debug

Produce verbose output.

--log=DESTINATION

Define destination for error and warning messages (file:PATH, journald:ID, or syslog:ID).

--systemd-cgroup

Use systemd for configuring cgroups.

--cgroup-manager=MANAGER

Specify cgroup manager (cgroupfs, systemd, or disabled).

CAVEATS

Requires root privileges or appropriate user namespace configuration. OCI bundle must be properly configured with config.json and rootfs. crun operates on OCI bundles, not container images directly.

HISTORY

crun was developed by Giuseppe Scrivano at Red Hat as a faster alternative to runc. First released around 2019, it gained adoption due to its performance benefits. It became the default runtime for Podman and is supported by Kubernetes through CRI-O.