v1.0.0~rc93 -- "I never could get the hang of Thursdays."

This is the last feature-rich RC release and we are in a feature-freeze until
1.0. 1.0.0~rc94 will be released in a few weeks with minimal bug fixes only,
and 1.0.0 will be released soon afterwards.

 * runc's cgroupv2 support is no longer considered experimental. It is now
   believed to be fully ready for production deployments. In addition, runc's
   cgroup code has been improved:
   - The systemd cgroup driver has been improved to be more resilient and
     handle more systemd properties correctly.
   - We now make use of openat2(2) when possible to improve the security of
     cgroup operations (in future runc will be wholesale ported to libpathrs to
     get this protection in all codepaths).

 * runc's mountinfo parsing code has been reworked significantly, making
   container startup times significantly faster and less wasteful in general.

 * runc now has special handling for seccomp profiles to avoid making new
   syscalls unusable for glibc. This is done by installing a custom prefix to
   all seccomp filters which returns -ENOSYS for syscalls that are newer than
   any syscall in the profile (meaning they have a larger syscall number).

   This should not cause any regressions (because previously users would simply
   get -EPERM rather than -ENOSYS, and the rule applied above is the most
   conservative rule possible) but please report any regressions you find as a
   result of this change -- in particular, programs which have special fallback
   code that is only run in the case of -EPERM.

 * runc now supports the following new runtime-spec features:
   - The umask of a container can now be specified.
   - The new Linux 5.9 capabilities (CAP_PERFMON, CAP_BPF, and
     CAP_CHECKPOINT_RESTORE) are now supported.
   - The "unified" cgroup configuration option, which allows users to explicitly
     specify the limits based on the cgroup file names rather than abstracting
     them through OCI configuration. This is currently limited in scope to

 * Various rootless containers improvements:
   - runc will no longer cause conflicts if a user specifies a custom device
     which conflicts with a user-configured device -- the user device takes
   - runc no longer panics if /sys/fs/cgroup is missing in rootless mode.

 * runc --root is now always treated as local to the current working directory.

 * The --no-pivot-root hardening was improved to handle nested mounts properly
   (please note that we still strongly recommend that users do not use
   --no-pivot-root -- it is still an insecure option).

 * A large number of code cleanliness and other various cleanups, including
   fairly large changes to our tests and CI to make them all run more

For packagers the following changes have been made which will have impact on
your packaging of runc:

 * The "selinux" and "apparmor" buildtags have been removed, and now all runc
   builds will have SELinux and AppArmor support enabled. Note that "seccomp"
   is still optional (though we very highly recommend you enable it).

 * make install DESTDIR= now functions correctly.

Thanks to the following people who made this release possible:

 * acetang <aceapril@126.com>
 * Adrian Reber <areber@redhat.com>
 * Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
 * Aleksa Sarai <cyphar@cyphar.com>
 * Amim Knabben <amim.knabben@gmail.com>
 * An Long <aisk1988@gmail.com>
 * Aos Dabbagh <aosdab@gmail.com>
 * Ashok Pon Kumar <ashokponkumar@gmail.com>
 * Cesar Talledo <ctalledo@nestybox.com>
 * Chaitanya Bandi <kbandi@cs.stonybrook.edu>
 * Cory Bennett <cbennett@netflix.com>
 * Daniel J Walsh <dwalsh@redhat.com>
 * Eduardo Vega <edvegavalerio@gmail.com>
 * Feng Sun <loyou85@gmail.com>
 * Giuseppe Scrivano <gscrivan@redhat.com>
 * Jeff Zvier <zvier20@gmail.com>
 * Kenta Tada <Kenta.Tada@sony.com>
 * Kir Kolyshkin <kolyshkin@gmail.com>
 * Manabu Sugimoto <Manabu.Sugimoto@sony.com>
 * Mauricio Vásquez <mauricio@kinvolk.io>
 * Michael Crosby <crosbymichael@gmail.com>
 * Mrunal Patel <mrunalp@gmail.com>
 * Paweł Szulik <pawel.szulik@intel.com>
 * Peter Hunt <pehunt@redhat.com>
 * Piotr Wagner <piotr.wagner@intel.com>
 * Sascha Grunert <sgrunert@suse.com>
 * SataQiu <1527062125@qq.com>
 * Sebastiaan van Stijn <github@gone.nl>
 * Shengjing Zhu <zhsj@debian.org>
 * Shukui Yang <keloyangsk@gmail.com>
 * wangtianxia <sometimesnaive@sjtu.edu.cn>
 * Wei Fu <fuweid89@gmail.com>
 * Xiaochen Shen <xiaochen.shen@intel.com>
 * Xiaodong Liu <liuxiaodong@loongson.cn>

Vote: +6 -0 #1
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
VERSION: release 1.0.0~rc93

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
1 file changed
tree: 5aaeccf51d48775a0dddf94ea34dc625059b9a02
  1. .github/
  2. contrib/
  3. docs/
  4. libcontainer/
  5. man/
  6. script/
  7. tests/
  8. types/
  9. vendor/
  10. .gitignore
  11. checkpoint.go
  13. create.go
  14. delete.go
  15. Dockerfile
  16. events.go
  17. exec.go
  18. go.mod
  19. go.sum
  20. init.go
  21. kill.go
  23. list.go
  24. main.go
  27. Makefile
  28. NOTICE
  29. notify_socket.go
  30. pause.go
  32. ps.go
  33. README.md
  34. restore.go
  35. rlimit_linux.go
  36. rootless_linux.go
  37. run.go
  38. SECURITY.md
  39. signals.go
  40. spec.go
  41. start.go
  42. state.go
  43. tty.go
  44. update.go
  45. utils.go
  46. utils_linux.go
  47. Vagrantfile.centos7
  48. Vagrantfile.fedora33


Go Report Card GoDoc CII Best Practices


runc is a CLI tool for spawning and running containers according to the OCI specification.


runc depends on and tracks the runtime-spec repository. We will try to make sure that runc and the OCI specification major versions stay in lockstep. This means that runc 1.0.0 should implement the 1.0 version of the specification.

You can find official releases of runc on the release page.


The reporting process and disclosure communications are outlined here.

Security Audit

A third party security audit was performed by Cure53, you can see the full report here.


runc currently supports the Linux platform with various architecture support. It must be built with Go version 1.13 or higher.

In order to enable seccomp support you will need to install libseccomp on your platform.

e.g. libseccomp-devel for CentOS, or libseccomp-dev for Ubuntu

# create a 'github.com/opencontainers' in your GOPATH/src
cd github.com/opencontainers
git clone https://github.com/opencontainers/runc
cd runc

sudo make install

You can also use go get to install to your GOPATH, assuming that you have a github.com parent folder already created under src:

go get github.com/opencontainers/runc
cd $GOPATH/src/github.com/opencontainers/runc
sudo make install

runc will be installed to /usr/local/sbin/runc on your system.

Build Tags

runc supports optional build tags for compiling support of various features, with some of them enabled by default (see BUILDTAGS in top-level Makefile).

To change build tags from the default, set the BUILDTAGS variable for make, e.g.

make BUILDTAGS='seccomp'
Build TagFeatureEnabled by defaultDependency
seccompSyscall filteringyeslibseccomp
nokmemdisable kernel memory accountingno

The following build tags were used earlier, but are now obsoleted:

  • apparmor (since runc v1.0.0-rc93 the feature is always enabled)
  • selinux (since runc v1.0.0-rc93 the feature is always enabled)

Running the test suite

runc currently supports running its test suite via Docker. To run the suite just type make test.

make test

There are additional make targets for running the tests outside of a container but this is not recommended as the tests are written with the expectation that they can write and remove anywhere.

You can run a specific test case by setting the TESTFLAGS variable.

# make test TESTFLAGS="-run=SomeTestFunction"

You can run a specific integration test by setting the TESTPATH variable.

# make test TESTPATH="/checkpoint.bats"

You can run a specific rootless integration test by setting the ROOTLESS_TESTPATH variable.

# make test ROOTLESS_TESTPATH="/checkpoint.bats"

You can run a test using your container engine's flags by setting CONTAINER_ENGINE_BUILD_FLAGS and CONTAINER_ENGINE_RUN_FLAGS variables.

# make test CONTAINER_ENGINE_BUILD_FLAGS="--build-arg http_proxy=http://yourproxy/" CONTAINER_ENGINE_RUN_FLAGS="-e http_proxy=http://yourproxy/"

Dependencies Management

runc uses Go Modules for dependencies management. Please refer to Go Modules for how to add or update new dependencies. When updating dependencies, be sure that you are running Go 1.14 or newer.

# Update vendored dependencies
make vendor
# Verify all dependencies
make verify-dependencies

Using runc

Please note that runc is a low level tool not designed with an end user in mind. It is mostly employed by other higher level container software.

Therefore, unless there is some specific use case that prevents the use of tools like Docker or Podman, it is not recommended to use runc directly.

If you still want to use runc, here's how.

Creating an OCI Bundle

In order to use runc you must have your container in the format of an OCI bundle. If you have Docker installed you can use its export method to acquire a root filesystem from an existing Docker container.

# create the top most bundle directory
mkdir /mycontainer
cd /mycontainer

# create the rootfs directory
mkdir rootfs

# export busybox via Docker into the rootfs directory
docker export $(docker create busybox) | tar -C rootfs -xvf -

After a root filesystem is populated you just generate a spec in the format of a config.json file inside your bundle. runc provides a spec command to generate a base template spec that you are then able to edit. To find features and documentation for fields in the spec please refer to the specs repository.

runc spec

Running Containers

Assuming you have an OCI bundle from the previous step you can execute the container in two different ways.

The first way is to use the convenience command run that will handle creating, starting, and deleting the container after it exits.

# run as root
cd /mycontainer
runc run mycontainerid

If you used the unmodified runc spec template this should give you a sh session inside the container.

The second way to start a container is using the specs lifecycle operations. This gives you more power over how the container is created and managed while it is running. This will also launch the container in the background so you will have to edit the config.json to remove the terminal setting for the simple examples below (see more details about runc terminal handling). Your process field in the config.json should look like this below with "terminal": false and "args": ["sleep", "5"].

        "process": {
                "terminal": false,
                "user": {
                        "uid": 0,
                        "gid": 0
                "args": [
                        "sleep", "5"
                "env": [
                "cwd": "/",
                "capabilities": {
                        "bounding": [
                        "effective": [
                        "inheritable": [
                        "permitted": [
                        "ambient": [
                "rlimits": [
                                "type": "RLIMIT_NOFILE",
                                "hard": 1024,
                                "soft": 1024
                "noNewPrivileges": true

Now we can go through the lifecycle operations in your shell.

# run as root
cd /mycontainer
runc create mycontainerid

# view the container is created and in the "created" state
runc list

# start the process inside the container
runc start mycontainerid

# after 5 seconds view that the container has exited and is now in the stopped state
runc list

# now delete the container
runc delete mycontainerid

This allows higher level systems to augment the containers creation logic with setup of various settings after the container is created and/or before it is deleted. For example, the container's network stack is commonly set up after create but before start.

Rootless containers

runc has the ability to run containers without root privileges. This is called rootless. You need to pass some parameters to runc in order to run rootless containers. See below and compare with the previous version.

Note: In order to use this feature, “User Namespaces” must be compiled and enabled in your kernel. There are various ways to do this depending on your distribution:

  • Confirm CONFIG_USER_NS=y is set in your kernel configuration (normally found in /proc/config.gz)
  • Arch/Debian: echo 1 > /proc/sys/kernel/unprivileged_userns_clone
  • RHEL/CentOS 7: echo 28633 > /proc/sys/user/max_user_namespaces

Run the following commands as an ordinary user:

# Same as the first example
mkdir ~/mycontainer
cd ~/mycontainer
mkdir rootfs
docker export $(docker create busybox) | tar -C rootfs -xvf -

# The --rootless parameter instructs runc spec to generate a configuration for a rootless container, which will allow you to run the container as a non-root user.
runc spec --rootless

# The --root parameter tells runc where to store the container state. It must be writable by the user.
runc --root /tmp/runc run mycontainerid


runc can be used with process supervisors and init systems to ensure that containers are restarted when they exit. An example systemd unit file looks something like this.

Description=Start My Container

ExecStart=/usr/local/sbin/runc run -d --pid-file /run/mycontainerid.pid mycontainerid
ExecStopPost=/usr/local/sbin/runc delete mycontainerid


More documentation


The code and docs are released under the Apache 2.0 license.