Separate runc binary version from libcontainer version

Now that the dependency on runc (libcontaienr) code has been reduced
considerably, it is probbaly ok to cut the version dependency between
libcontainer and the runc binary that is supported.

This patch separates the runc binary version from the version of
libcontainer that is defined in go.mod, and updates the documentation
accordingly.

The RUNC_COMMIT variable in the install-runc script is renamed to
RUNC_VERSION to encourage using tagged versions, and the Dockerfile
in contrib is updated to allow building with a custom version.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

BUILDING.md

@@ -180,7 +180,13 @@ RUN apt-get update && \
 
 ```
 
-In our Docker container we will use a specific `runc` build which includes [seccomp](https://en.wikipedia.org/wiki/seccomp) and [apparmor](https://en.wikipedia.org/wiki/AppArmor) support. Hence why our Dockerfile includes `libseccomp-dev` as a dependency (apparmor support doesn't require external libraries). Please refer to [RUNC.md](/docs/RUNC.md) for the currently supported version of `runc` that is used by containerd.
+In our Docker container we will build `runc` build, which includes
+[seccomp](https://en.wikipedia.org/wiki/seccomp), [SELinux](https://en.wikipedia.org/wiki/Security-Enhanced_Linux),
+and [AppArmor](https://en.wikipedia.org/wiki/AppArmor) support. Seccomp support
+in runc requires `libseccomp-dev` as a dependency (AppArmor and SELinux support
+do not require external libraries at build time). Refer to [RUNC.md](docs/RUNC.md)
+in the docs directory to for details about building runc, and to learn about
+supported versions of `runc` as used by containerd.
 
 Let's suppose you build an image called `containerd/build` from the above Dockerfile. You can run the following command:
 

README.md

@@ -49,7 +49,8 @@ Please be aware: nightly builds might have critical bugs, it's not recommended f
 
 Runtime requirements for containerd are very minimal. Most interactions with
 the Linux and Windows container feature sets are handled via [runc](https://github.com/opencontainers/runc) and/or
-OS-specific libraries (e.g. [hcsshim](https://github.com/Microsoft/hcsshim) for Microsoft). The current required version of `runc` is always listed in [RUNC.md](/docs/RUNC.md).
+OS-specific libraries (e.g. [hcsshim](https://github.com/Microsoft/hcsshim) for Microsoft).
+The current required version of `runc` is described in [RUNC.md](docs/RUNC.md).
 
 There are specific features
 used by containerd core code and snapshotters that will require a minimum kernel

contrib/Dockerfile.test

@@ -5,6 +5,10 @@
 # 2.) docker run -it --privileged -v /tmp:/tmp --tmpfs /var/lib/containerd-test containerd-test  bash
 # 3.) $ make binaries install test
 #
+# Use the RUNC_VERSION build-arg to build with a custom version of runc, for example,
+# to build runc v1.0.0-rc93, use:
+#
+# docker build -t containerd-test --build-arg RUNC_VERSION=v1.0.0-rc93 -f Dockerfile.test ../
 
 ARG GOLANG_VERSION=1.15.8
 
@@ -32,8 +36,9 @@ RUN apt-get update && apt-get install -y \
     libseccomp-dev \
   --no-install-recommends
 
-COPY go.mod go.mod
 COPY script/setup/install-runc install-runc
+# Allow overriding the version of runc to install through build-args
+ARG RUNC_VERSION
 ARG GOPROXY=direct
 RUN ./install-runc
 

docs/RUNC.md

@@ -1,13 +1,28 @@
-containerd is built with OCI support and with support for advanced features provided by [runc](https://github.com/opencontainers/runc).
+containerd is built with OCI support and with support for advanced features
+provided by [runc](https://github.com/opencontainers/runc).
 
-We depend on a specific `runc` version when dealing with advanced features.  You should have a specific runc build for development.  The current supported runc commit is described in [`go.mod`](../go.mod). Please refer to the line that starts with `github.com/opencontainers/runc`.
+Development (`-dev`) and pre-releases of containerd may depend features in `runc`
+that have not yet been released, and may require a specific runc build. The version
+of runc that is tested against in our CI can be found in the `RUNC_VERSION` variable
+in the [`script/setup/install-runc`](../script/setup/install-runc) script, which
+may point to a git-commit (for pre releases) or tag in the runc repository.
 
-For more information on how to clone and build runc see the runc Building [documentation](https://github.com/opencontainers/runc#building).
+For regular (non-pre-)releases of containerd releases, we attempt to use released
+(tagged) versions of runc. We recommend using a version of runc that's equal to
+or higher than the version of runc described in [`script/setup/install-runc`](../script/setup/install-runc).
 
-Note: before building you may need to install additional support, which will vary by platform. For example, you may need to install `libseccomp` e.g. `libseccomp-dev` for Ubuntu.
+If you encounter any runtime errors, make sure your runc is in sync with the
+commit or tag provided in that file.
 
 ## building
 
+> For more information on how to clone and build runc also refer to the runc
+> building [documentation](https://github.com/opencontainers/runc#building).
+
+Before building runc you may need to install additional build dependencies, which
+will vary by platform. For example, you may need to install `libseccomp` e.g.
+`libseccomp-dev` for Ubuntu.
+
 From within your `opencontainers/runc` repository run:
 
 ```bash
@@ -29,7 +44,5 @@ build-tag to enable seccomp support, for example:
 make BUILDTAGS='nokmem seccomp' && make install
 ```
 
-For details about the `nokmem` build-tag, refer to [opencontainers/runc#2594](https://github.com/opencontainers/runc/pull/2594).
+For details about the `nokmem` build-tag, refer to the discussion on [opencontainers/runc#2594](https://github.com/opencontainers/runc/pull/2594).
 For further details on building runc, refer to the [build instructions in the runc README](https://github.com/opencontainers/runc#building).
-
-After an official runc release we will start pinning containerd support to a specific version but various development and testing features may require a newer runc version than the latest release.  If you encounter any runtime errors, please make sure your runc is in sync with the commit/tag provided in this document.

script/setup/install-runc

@@ -21,13 +21,14 @@
 set -eu -o pipefail
 
 function install_runc() {
-	RUNC_COMMIT=$(grep opencontainers/runc "$GOPATH"/src/github.com/containerd/containerd/go.mod | awk '{print $2}')
+	# When updating RUNC_VERSION, consider updating the runc module in go.mod as well
+	: "${RUNC_VERSION:=v1.0.0-rc93}"
 
 	TMPROOT=$(mktemp -d)
 	git clone https://github.com/opencontainers/runc.git "${TMPROOT}"/runc
 	pushd "${TMPROOT}"/runc
-	git checkout "${RUNC_COMMIT}"
-	make runc
+	git checkout "${RUNC_VERSION}"
+	make
 	make install
 	popd
 	rm -fR "${TMPROOT}"