docs: update supported OS distros

* correct base container image info
* show RHEL as deprecated

Change-Id: Ie8eec4cb4e29e7f659228e2792c13c01dfb4a41c
(cherry picked from commit b69240ca4b)

doc/source/admin/image-building.rst

@@ -20,7 +20,8 @@ In general, images are built like this:
 
    kolla-build
 
-By default, the above command would build all images based on CentOS image.
+By default, the above command would build all images based on a CentOS Stream
+image.
 
 The operator can change the base distro with the ``-b`` option:
 
@@ -32,7 +33,7 @@ There are following distros (bases) available for building images:
 
 - centos
 - debian
-- rhel
+- rhel (deprecated)
 - ubuntu
 
 See the :ref:`support matrix <support-matrix-base-images>` for information on

doc/source/support_matrix.rst

@@ -14,14 +14,14 @@ Supported base images
 
 The following base container images are supported:
 
-============= ============ ================
+================== =============================== ================
-Distribution  Default base Default base tag
+Distribution       Default base                    Default base tag
-============= ============ ================
+================== =============================== ================
-CentOS 8      centos       8
+CentOS Stream 8    quay.io/centos/centos           stream8
-Debian Buster debian       10
+Debian Buster      debian                          bullseye
-RHEL 8        rhel         8
+RHEL8 (deprecated) registry.access.redhat.com/ubi8 latest
-Ubuntu Focal  ubuntu       20.04
+Ubuntu Focal       ubuntu                          20.04
-============= ============ ================
+================== =============================== ================
 
 The remainder of this document outlines which images are supported on which of
 these distribution.