update examples with more current distros

Use more current versions of distros in the examples, because CentOS 7
will reach EOL soon, and there's a new Ubuntu LTS release.

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

README.md

@@ -9,12 +9,31 @@ make clean
 make docker.io/library/<distro>:<version> [docker.io/library/<distro>:<version> ...]
 
 # for example:
-# make docker.io/library/centos:7
-# make docker.io/library/ubuntu:jammy
+# make quay.io/centos/centos:stream9
+# make docker.io/library/ubuntu:24.04
 ```
 
 After build completes, packages can be found in the `build` directory.
 
+## Specifying the version to build
+
+By default, packages are built from HEAD of the `release/1.7` branch, as
+defines in [common/common.mk]. The version of runc defaults to the version
+as specified by the containerd project through the [script/setup/runc-version]
+file in the containerd repository.
+
+Use the `REF` and `RUNC_REF` make variables to specify the versions to build.
+The provided values must be a valid Git reference, which can be a commit
+(e.g., `ae71819` or `ae71819c4f5e67bb4d5ae76a6b735f29cc25774e`), branch
+(e.g. `main` or `release/1.7`), or tag (e.g. `v1.7.18`).
+
+The following example builds packages for containerd v1.7.18 with
+runc v1.1.12 for Ubuntu 24.04:
+
+```bash
+make REF=v1.7.18 RUNC_REF= docker.io/library/ubuntu:24.04
+```
+
 ## Building a package from a local source directory
 
 Specify the path to the local source directory using `CONTAINERD_DIR` and/or
@@ -35,3 +54,7 @@ make REF=HEAD CONTAINERD_DIR=/home/me/go/src/github.com/containerd/containerd do
 
 * [deb package maintainers guide](debian/README.md)
 * [rpm package maintainers guide](rpm/README.md)
+
+
+[common/common.mk]: https://github.com/docker/containerd-packaging/blob/main/common/common.mk#L19
+[script/setup/runc-version]: https://github.com/containerd/containerd/blob/v1.7.18/script/setup/runc-version

debian/README.md

@@ -9,7 +9,7 @@ repository.
 Afterwards test if you can actually build the release with (for example):
 
 ```bash
-make REF=${TAG} docker.io/library/ubuntu:jammy
+make REF=${TAG} docker.io/library/ubuntu:24.04
 ```
 
 If you can actually build the package then start prepping
@@ -31,11 +31,11 @@ VERSION is already there.
 Releases can then be built with:
 
 ```bash
-make REF=${TAG} docker.io/library/ubuntu:jammy
+make REF=${TAG} docker.io/library/ubuntu:24.04
 ```
 
 or
 
 ```bash
-make REF=${TAG} BUILD_IMAGE=docker.io/library/ubuntu:jammy
+make REF=${TAG} BUILD_IMAGE=docker.io/library/ubuntu:24.04
 ```

rpm/README.md

@@ -9,7 +9,7 @@ repository.
 Afterwards test if you can actually build the release with (for example):
 
 ```bash
-make REF=${TAG} docker.io/library/centos:7
+make REF=${TAG} quay.io/centos/centos:stream9
 ```
 
 If you can actually build the package then start prepping
@@ -31,11 +31,11 @@ VERSION is already there.
 Releases can then be built with:
 
 ```bash
-make REF=${TAG} docker.io/library/centos:7
+make REF=${TAG} quay.io/centos/centos:stream9
 ```
 
 or
 
 ```bash
-make REF=${TAG} BUILD_IMAGE=docker.io/library/centos:7
+make REF=${TAG} BUILD_IMAGE=quay.io/centos/centos:stream9
 ```