Update readme's

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

README.md

@@ -2,12 +2,33 @@
 
 # Usage:
 
-## For Developers:
+To build a distro-specific package (rpm or deb):
 
-Making a developer package is as simple as:
+```bash
+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:18.04
+```
+
+After build completes, packages can be found in the `build` directory.
+
+## Building a package from a local source directory
+
+Specify the path to the local source directory using `CONTAINERD_DIR` and/or
+`RUNC_DIR`:
+
+```shell
+make REF=<git reference> CONTAINERD_DIR=<path to repository> docker.io/library/<distro>:<version>
+```
+
+For example:
 
 ```shell
-make CONTAINERD_DIR=${GOPATH}/src/github.com/containerd/containerd <all|rpm|deb>
+make clean
+make REF=HEAD CONTAINERD_DIR=/home/me/go/src/github.com/containerd/containerd docker.io/library/ubuntu:18.04
 ```
 
 ## For package maintainers:

debian/README.md

@@ -6,29 +6,36 @@ For releases you should first have a tagged release on the
 [containerd](https://github.com/containerd/containerd/releases)
 repository.
 
-Afterwards test if you can actually build the release with:
+Afterwards test if you can actually build the release with (for example):
 
-```
-make REF=${TAG} deb
+```bash
+make REF=${TAG} docker.io/library/ubuntu:18.04
 ```
 
 If you can actually build the package then start prepping
-your release by adding an entry in the [`debian/changelog`](changelog) with:
+your release by adding an entry in the [`debian/changelog`](changelog) with the
+format:
 
-```
+```bash
 ./scripts/new-deb-release <VERSION>
 ```
 
 This will add an entry into the changelog for the specified VERSION
 and will also increment the debian packaging version if the specified
 VERSION is already there.
 
-**NOTE**: Make sure to fill out the bullets for the changelog
+> **NOTE**: Make sure to fill out the bullets for the changelog
 
 ## Building the release:
 
 Releases can then be built with:
 
+```bash
+make REF=${TAG} docker.io/library/centos:7
 ```
-make REF=${TAG} deb
+
+or
+
+```bash
+make REF=${TAG} BUILD_IMAGE=docker.io/library/ubuntu:18.04
 ```

rpm/README.md

@@ -6,30 +6,36 @@ For releases you should first have a tagged release on the
 [containerd](https://github.com/containerd/containerd/releases)
 repository.
 
-Afterwards test if you can actually build the release with:
+Afterwards test if you can actually build the release with (for example):
 
-```
-make REF=${TAG} rpm
+```bash
+make REF=${TAG} docker.io/library/centos:7
 ```
 
 If you can actually build the package then start prepping
-your release by adding a changelog entry in the
+your release by adding an changelog entry in the
 [`rpm/containerd.spec`](containerd.spec) with the format:
 
-```
+```bash
 ./scripts/new-rpm-release <VERSION>
 ```
 
 This will add an entry into the changelog for the specified VERSION
 and will also increment the rpm packaging version if the specified
 VERSION is already there.
 
-**NOTE**: Make sure to fill out the bullets for the changelog
+> **NOTE**: Make sure to fill out the bullets for the changelog
 
 ## Building the release:
 
 Releases can then be built with:
 
+```bash
+make REF=${TAG} docker.io/library/centos:7
 ```
-make REF=${TAG} rpm
+
+or
+
+```bash
+make REF=${TAG} BUILD_IMAGE=docker.io/library/centos:7
 ```