README: simplify build instructions

The podman line is quite difficult to read and to maintain.
Moreover, it was using SELinux relabeling incorrectly according to
podman's docs[1]:
"""
Note: Do not relabel system files and directories.
For these types of containers we recommend disabling SELinux separation.
The option --security-opt label=disable disables SELinux separation for
the container.
"""

Also, not everybody is using podman, some people are using docker.

Finally, kas package provides a shell script that prepares the whole
container startup command line by itself, called kas-container. So
let's use that one instead.

[1] https://docs.podman.io/en/latest/markdown/podman-run.1.html#volume-v-source-volume-host-dir-container-dir-options

Reported-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>

1 files changed, 11 insertions, 5 deletions

diff --git a/README b/README
index 4a5cadf..9a0199c 100644
--- a/README
+++ b/README
@@ -37,14 +37,20 @@ kas-theobroma.yml is a configuration file to be used by kas
 (https://github.com/siemens/kas) which sets up everything one needs to build the
 extended image that can run on the supported boards listed above.
 
-One builds the image by running the following commands:
+It is recommended to install the kas package through the distro manager:
 
-$ podman run -it --rm --userns=keep-id -e USER_ID=$UID -e
-GROUP_ID=$GID -w $PWD/.. -v $PWD/..:$PWD/..:rw,Z --tmpfs /tmp
-ghcr.io/siemens/kas/kas:4.0 build meta-theobroma-systems-extended/kas-theobroma.yml
+	apt-get install -y kas
+
+or via pip:
+
+	python3 -m pip install kas
+
+The image can then be built with:
+
+	KAS_IMAGE_VERSION="4.0" kas-container build kas-theobroma.yml
 
 Once the build has finished, the artifacts will be available in
-../build/tmp/deploy/images/ringneck-haikou/ directory.
+build/tmp/deploy/images/ringneck-haikou/ directory.
 
 One can directly flash the .wic image on an SD card with the following command: