crun - a fast and lightweight OCI runtime
crun [global options] command [command options] [arguments...]
crun is a command line program for running Linux containers that follow the Open Container Initiative (OCI) format.
create
Create a container. The runtime detaches from the container process
once the container environment is created. It is necessary to
successively use start for starting the container.
delete Remove definition for a container.
exec Exec a command in a running container.
list List known containers.
kill Send the specified signal to the container init process. If no signal is specified, SIGTERM is used.
ps Show the processes running in a container.
run Create and immediately start a container.
spec Generate a configuration file.
start Start a container that was previously created. A container cannot be started multiple times.
state Output the state of a container.
pause Pause all the processes in the container.
resume Resume the processes in the container.
update Update container resource constraints.
By default, when running as root user, crun saves its state under the /run/crun directory. As unprivileged user, instead the XDG_RUNTIME_DIR environment variable is honored, and the directory $XDG_RUNTIME_DIR/crun is used. The global option --root overrides this setting.
--debug Produce verbose output.
--log=LOG-DESTINATION Define the destination for the error and warning messages generated by crun. If the error happens late in the container init process, when crun already stopped watching it, then it will be printed to the container stderr.
It is specified in the form BACKEND:SPECIFIER.
These following backends are supported:
- file:PATH
- journald:IDENTIFIER
- syslog:IDENTIFIER
If no backend is specified, then file: is used by default.
--log-format=FORMAT Define the format of the log messages. It can either be text, or json. The default is text.
--no-pivot
Use chroot(2) instead of pivot_root(2) when creating the container.
This option is not safe, and should be avoided.
--root=DIR Defines where to store the state for crun containers.
--systemd-cgroup Use systemd for configuring cgroups. If not specified, the cgroup is created directly using the cgroupfs backend.
--cgroup-manager=MANAGER Specify what cgroup manager must be used. Permitted values are cgroupfs, systemd and disabled.
-?, --help Print a help list.
--usage Print a short usage message.
-V, --version Print program version
crun [global options] create [options] CONTAINER
--bundle=BUNDLE Path to the OCI bundle, by default it is the current directory.
--config=FILE Override the configuration file to use. The default value is config.json.
--console-socket=SOCKET Path to a UNIX socket that will receive the master end of the tty for the container.
--no-new-keyring Keep the same session key
--preserve-fds=N Additional number of FDs to pass into the container.
--pid-file=PATH Path to the file that will contain the container process PID.
crun [global options] run [options] CONTAINER
--bundle=BUNDLE Path to the OCI bundle, by default it is the current directory.
--config=FILE Override the configuration file to use. The default value is config.json.
--console-socket=SOCKET Path to a UNIX socket that will receive the master end of the tty for the container.
--no-new-keyring Keep the same session key.
--preserve-fds=N Additional number of FDs to pass into the container.
--pid-file=PATH Path to the file that will contain the container process PID.
--detach Detach the container process from the current session.
crun [global options] delete [options] CONTAINER
--force Delete the container even if it is still running.
--regex=REGEX Delete all the containers that satisfy the specified regex.
crun [global options] exec [options] CONTAINER CMD
--console-socket=SOCKET Path to a UNIX socket that will receive the master end of the tty for the container.
--cwd=PATH Set the working directory for the process to PATH.
--cap=CAP Specify an additional capability to add to the process.
--detach Detach the container process from the current session.
--env=ENV Specify an environment variable.
--preserve-fds=N Additional number of FDs to pass into the container.
--process=FILE Path to a file containing the process JSON configuration.
--pid-file=PATH Path to the file that will contain the new process PID.
-t --tty Allocate a pseudo TTY.
-u USERSPEC --user=USERSPEC Specify the user in the form UID[:GID].
crun [global options] list [options]
-q --quiet Show only the container ID.
crun [global options] kill [options] CONTAINER SIGNAL
--all Kill all the processes in the container.
--regex=REGEX Kill all the containers that satisfy the specified regex.
crun [global options] ps [options]
--format=FORMAT
Specify the output format. It must be either table or json.
By default table is used.
crun [global options] spec [options]
--rootless Generate a config.json file that is usable by an unprivileged user.
crun [global options] update [options] CONTAINER
--blkio-weight=VALUE Specifies per cgroup weight.
--cpu-period=VALUE CPU CFS period to be used for hardcapping.
--cpu-quota**=VALUE CPU CFS hardcap limit.
--cpu-rt-period=VALUE CPU realtime period to be used for hardcapping.
--cpu-rt-runtime=VALUE CPU realtime hardcap limit.
--cpu-share=VALUE CPU shares.
--cpuset-cpus=VALUE CPU(s) to use.
--cpuset-mems=VALUE Memory node(s) to use.
--kernel-memory=VALUE Kernel memory limit.
--kernel-memory-tcp=VALUE Kernel memory limit for TCP buffer.
--memory=VALUE Memory limit.
--memory-reservation=VALUE Memory reservation or soft_limit.
--memory-swap=VALUE Total memory usage.
--pids-limit=VALUE Maximum number of pids allowed in the container.
-r, --resources=FILE Path to the file containing the resources to update.
If the annotation run.oci.seccomp_fail_unknown_syscall is present, then crun
will fail when an unknown syscall is encountered in the seccomp configuration.
If the annotation run.oci.keep_original_groups is present, then crun
will skip the setgroups syscall that is used to either set the
additional groups specified in the OCI configuration, or to reset the
list of additional groups if none is specified.
Specify the offset to be written to /proc/self/timens_offsets when creating a time namespace.
Override the name for the systemd sub cgroup created under the systemd scope, so the final cgroup will be like:
/sys/fs/cgroup/$PATH/$SUBGROUPWhen it is set to the empty string, a sub cgroup is not created.
If not specified, it defaults to container on cgroup v2, and to ""
on cgroup v1.
e.g.
/sys/fs/cgroup//system.slice/foo-352700.scope/containerIf the tmpcopyup option is specified for a tmpfs, then the path that
is shadowed by the tmpfs mount is recursively copied up to the tmpfs
itself.
When running as user different than root, an user namespace is
automatically created even if it is not specified in the config file.
The current user is mapped to the ID 0 in the container, and any
additional id specified in the files /etc/subuid and /etc/subgid
is automatically added starting with ID 1.
crun has some basic support for cgroup v2. Since the OCI spec is designed for cgroup v1, in some cases there is need to convert from the cgroup v1 configuration to cgroup v2.
These are the OCI resources currently supported with cgroup v2 and how they are converted when needed from the cgroup v1 configuration.
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| limit | memory.max | y = x | |
| swap | memory.swap_max | y = x | |
| reservation | memory.low | y = x |
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| limit | pids.max | y = x |
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| shares | cpu.weight | y = (1 + ((x - 2) * 9999) / 262142) | convert from [2-262144] to [1-10000] |
| period | cpu.max | y = x | period and quota are written together |
| quota | cpu.max | y = x | period and quota are written together |
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| weight | io.bfq.weight | y = (1 + (x - 10) * 9999 / 990) | convert linearly from [10-1000] to [1-10000] |
| weight_device | io.bfq.weight | y = (1 + (x - 10) * 9999 / 990) | convert linearly from [10-1000] to [1-10000] |
| rbps | io.max | y=x | |
| wbps | io.max | y=x | |
| riops | io.max | y=x | |
| wiops | io.max | y=x |
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| cpus | cpuset.cpus | y = x | |
| mems | cpuset.mems | y = x |
| OCI (x) | cgroup 2 value (y) | conversion | comment |
|---|---|---|---|
| <PAGE_SIZE>.limit_in_bytes | hugetlb.<PAGE_SIZE>.max | y = x |