[isar-cip-core][RFC v2 4/4] doc/README.swupdate.md: Update steps to test Delta software Update

[Adithya Balakumar <Adithya.Balakumar@toshiba-tsip.com>]

This change includes steps to verify Delta Software Update with
rdiff_image and delta handler

Signed-off-by: Adithya Balakumar <Adithya.Balakumar@toshiba-tsip.com>
---
 doc/README.swupdate.md | 59 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/doc/README.swupdate.md b/doc/README.swupdate.md
index b7e13f7..3862649 100644
--- a/doc/README.swupdate.md
+++ b/doc/README.swupdate.md
@@ -360,6 +360,65 @@ user variables:
 
 ```
 
+# Building and testing the CIP Core image for Delta Software Update
+
+Set up `kas-container` as described in the [top-level README](../README.md), and then proceed with the following steps.
+
+First build an image using the following command:
+```
+host$ ./kas-container build kas-cip.yml:kas/board/qemu-amd64.yml:kas/opt/ebg-swu.yml:kas/opt/rt.yml
+```
+
+## Delta Software Update using rdiff_image handler
+
+Creating an delta update file for rdiff_image handler requires a reference image (against which the delta is computed). In this case, the image built in the previous section can be used as the reference image artifact. By default the `DELTA_UPDATE_TYPE` is set to `rdiff` and `DELTA_RDIFF_REF_IMAGE` is set to the path `image-v1/<artifact-name>.squashfs` (or <artifact-name>.verity in the case of Secure boot enabled image).
+Copy the reference artifact to the mentioned directory in project folder.
+
+Custom artifact path can be set in `DELTA_RDIFF_REF_IMAGE` manually by adding the variable in the `swupdate.yml` file.
+
+Build the image with the modification as shown above with the following command:
+```
+KAS_BUILD_DIR=image2 ./kas-container build kas-cip.yml:kas/board/qemu-amd64.yml:kas/opt/ebg-swu.yml
+```
+Now start the first image (which does not contain the packages vim and nano), run the following commands:
+```
+host$ DISTRO_RELEASE=bookworm SWUPDATE_BOOT=y ./start-qemu.sh amd64
+```
+Copy `cip-core-image-cip-core-bookworm-qemu-amd64-delta.swu` file from `image2/tmp/deploy/images/qemu-amd64/` folder into the running system:
+```
+host$ cd image2/tmp/deploy/images/qemu-amd64/
+host$ scp -P 22222 ./cip-core-image-cip-core-bookworm-qemu-amd64-delta.swu root@localhost:
+```
+
+### Delta Software Update Verification
+
+Follow the steps mentioned in the section [SWUpdate verification](#swupdate-verification) for verification.
+
+## Delta Software Update using delta handler
+
+Currently zchunk based delta updates are supported only in Sid images.
+For Delta update with zchunk, set the variable `DELTA_ZCK_URL` with the URL of the zck file that is hosted in a http server and set the `DELTA_UPDATE_TYPE` to `zchunk` im `swupdate.yml` file.
+
+Build the image with the modification as shown above with the following command:
+```
+KAS_BUILD_DIR=image2 ./kas-container build kas-cip.yml:kas/board/qemu-amd64.yml:kas/opt/ebg-swu.yml
+```
+Now start the first image (which does not contain the packages vim and nano), run the following commands:
+```
+host$ DISTRO_RELEASE=bookworm SWUPDATE_BOOT=y ./start-qemu.sh amd64
+```
+Copy `cip-core-image-cip-core-bookworm-qemu-amd64-delta.swu` file from `image2/tmp/deploy/images/qemu-amd64/` folder into the running system:
+```
+host$ cd image2/tmp/deploy/images/qemu-amd64/
+host$ scp -P 22222 ./cip-core-image-cip-core-bookworm-qemu-amd64-delta.swu root@localhost:
+```
+The `cip-core-image-cip-core-bookworm-qemu-amd64.zck` file must be hosted in a server.
+
+### Delta Software Update Verification
+
+Follow the steps mentioned in the section [Delta Software Update Verification](#delta-software-update-verification) for verification.
+
+
 # Building and testing the CIP Core image for BBB
 
 Follow the steps mentioned in the section [Building and testing the CIP Core image](README.swupdate.md#building-and-testing-the-cip-core-image) for creating images and .swu files.
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