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.
checkpoint Checkpoint a running container using CRIU
restore Restore a container from a checkpoint
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 ptmx 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 ptmx 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
--apparmor=PROFILE Set the apparmor profile for the process.
--console-socket=SOCKET Path to a UNIX socket that will receive the ptmx 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.
--no-new-privs Set the no new privileges value for the process.
--preserve-fds=N Additional number of FDs to pass into the container.
--process=FILE Path to a file containing the process JSON configuration.
--process-label=VALUE Set the asm process label for the process commonly used with selinux.
--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]
-b DIR --bundle=DIR Path to the root of the bundle dir (default ".").
--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.
crun [global options] checkpoint [options] CONTAINER
--image-path=DIR Path for saving CRIU image files
--work-path=DIR Path for saving work files and logs
--leave-running Leave the process running after checkpointing
--tcp-established Allow open TCP connections
--ext-unix-sk Allow external UNIX sockets
--shell-job Allow shell jobs
crun [global options] restore [options] CONTAINER
-b DIR --bundle=DIR Container bundle directory (default ".")
--image-path=DIR Path for saving CRIU image files
--work-path=DIR Path for saving work files and logs
--tcp-established Allow open TCP connections
--ext-unix Allow external UNIX sockets
--shell-job Allow shell jobs
--detach Detach from the container's process
--pid-file=FILE Where to write the PID of the container
If the annotation run.oci.seccomp.receiver=PATH is specified, the
seccomp listener is sent to the UNIX socket listening on the specified
path. It can also set with the RUN_OCI_SECCOMP_RECEIVER environment variable.
It is an experimental feature, and the annotation will be removed once
it is supported in the OCI runtime specs. It must be an absolute path.
If the annotation run.oci.seccomp.plugins=PLUGIN1[:PLUGIN2]... is specified, the
seccomp listener fd is handled through the specified plugins. The
plugin must either be an absolute path or a file name that is looked
up by ldopen(3). More information on how the lookup is performed
are available on the ld.so(8) man page.
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.seccomp_bpf_data is present, then crun
ignores the seccomp section in the OCI configuration file and use the specified data
as the raw data to the seccomp(SECCOMP_SET_MODE_FILTER) syscall.
The data must be encoded in base64.
It is an experimental feature, and the annotation will be removed once it is supported in the OCI runtime specs.
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.
If the annotation run.oci.systemd.force_cgroup_v1=/PATH is present, then crun
will override the specified mount point /PATH with a cgroup v1 mount
made of a single hierarchy none,name=systemd.
It is useful to run on a cgroup v2 system containers using older
versions of systemd that lack support for cgroup v2.
Note: Your container host has to have the cgroup v1 mount already present, otherwise this will not work. If you want to run the container rootless, the user it runs under has to have permissions to this mountpoint.
For example, as root:
mkdir /sys/fs/cgroup/systemd
mount cgroup -t cgroup /sys/fs/cgroup/systemd -o none,name=systemd,xattr
chown -R the_user.the_user /sys/fs/cgroup/systemdSpecify 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/$SUBGROUPWhen it is set to the empty string, a sub cgroup is not created.
If not specified, it defaults to container on cgroup v2, and to ""
on cgroup v1.
e.g.
/sys/fs/cgroup//system.slice/foo-352700.scope/containerIf the run.oci.systemd.subgroup annotation is specified, yet another
sub-cgroup is created and the container process is moved here.
/sys/fs/cgroup/$PATH/$SUBGROUP/$DELEGATED-CGROUPThe runtime doesn't apply any limit to the $DELEGATED-CGROUP
sub-cgroup, the runtime uses only $PATH/$SUBGROUP.
The container payload fully manages $DELEGATE-CGROUP, the limits
applied to $PATH/$SUBGROUP still applies to $DELEGATE-CGROUP.
Since cgroup delegation is not safe on cgroup v1, this option is supported only on cgroup v2.
If the annotation run.oci.hooks.stdout is present, then crun
will open the specified file and use it as the stdout for the hook
processes. The file is opened in append mode and it is created if it
doesn't already exist.
If the annotation run.oci.hooks.stderr is present, then crun
will open the specified file and use it as the stderr for the hook
processes. The file is opened in append mode and it is created if it
doesn't already exist.
It is an experimental feature.
If specified, run the specified handler for execing the container.
The only supported value is krun. When krun is specified, the
libkrun.so shared object is loaded and it is used to launch the
container using libkrun.
If 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.
If the configuration specifies a new user namespace made of a single mapping to the root user, but either the UID or the GID are set as nonzero then crun automatically creates another user namespace to map the root user to the specified UID and GID.
It enables running unprivileged containers with UID and GID different than zero, even when a single UID and GID are available, e.g. rootless users on a system without newuidmap/newgidmap.
Note: cgroup v2 does not yet support control of realtime processes and the cpu controller can only be enabled when all RT processes are in the root cgroup. This will make crun fail while running alongside RT processes.
If the cgroup configuration found is for cgroup v1, crun attempts a conversion when running on a cgroup v2 system.
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 - memory_limit | the swap limit on cgroup v1 includes the memory usage too |
| 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 = x | |
| weight_device | io.bfq.weight | y = x | |
| 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 |