Added all readme, help text and configs

README.md

@@ -68,6 +68,7 @@ Options:
 -F     Only compose up the specific container, not the whole compose stack (useful for master-compose structure).
 -h     Print this Help.
 -i     Inform - send a preconfigured notification.
+-k N   DaysKept - enable backups of images prior to update and prunes backups older than N days.
 -I     Prints custom releasenote urls alongside each container with updates in CLI output (requires urls.list).
 -l     Only include containers with label set. See readme.
 -m     Monochrome mode, no printf colour codes and hides progress bar.
@@ -245,6 +246,22 @@ The `urls.list` file is just an example and I'd gladly see that people contribut
 Pass `-x N` where N is number of subprocesses allowed, experiment in your environment to find a suitable max!  
 Change the default value by editing the `MaxAsync=N` variable in `dockcheck.sh`. To disable the subprocess function set `MaxAsync=0`.
 
+## Image Backups `-k` backup previous images as custom (retagged) images for easy rollback
+When the option `DaysKept` is set **dockcheck** will store the image being updated as a backup, retagged with a different name and stored for the amount of days configured (*DaysKept*) before being pruned.
+Let's say we're updating `b4bz/homer:latest` - then before replacing the current image it will be retagged with the name `dockcheck/homer:2025-10-26_1132_latest`
+- `dockcheck` as repo name to not interfere with others.
+- `homer` is the image.
+- `2025-10-26_1132` is the time when running the script.
+- `latest` is the tag of the image.
+
+Then if an update breaks, you could temporarily roll back to the previoius working state by changing the docker compose image to `image: dockcheck/homer:2025-10-26_1132_latest` and get it up and running again, then continue troubleshooting the breaking update.  
+
+The backed up images will be removed if they're older than *DaysKept* value (passed as `-k N` or set in the `dockcheck.config` with `DaysKept=N`) and then pruned.  
+If configured for eg. 7 days, force earlier cleaning by just passing a lower number of days, eg. `-k 2` to clean everything older than 2 days.  
+Backed up images will not be removed if neither `-k` flag nor `DaysKept` config variable is set.
+
+The `docker images` or `docker image ls` commands will show all currently backed up images.  
+To manually remove any backed up images, do `docker rmi dockcheck/homer:2025-10-26_1132_latest`.  
 
 ## Extra plugins and tools:
 

default.config

@@ -28,6 +28,7 @@
 #CurlRetryCount=3    # Max number of curl retries
 #CurlConnectTimeout=5    # Time to wait for curl to establish a connection before failing
 #DisplaySourcedFiles=false    # Display what files are being sourced/used
+#DaysKept=7    # Enable backups of images and removes backups older than N days.
 
 ### Notify settings
 ## All commented values are examples only. Modify as needed.

dockcheck.sh

@@ -44,6 +44,7 @@ Help() {
   echo "-I     Prints custom releasenote urls alongside each container with updates in CLI output (requires urls.list)."
   echo "-k N   Number of days to store image backups before pruning - this also enables the backup function."
   echo "-l     Only include containers with label set. See readme."
+  echo "-k N   DaysKept - enable backups of images prior to update and prunes backups older than N days."
   echo "-m     Monochrome mode, no printf colour codes and hides progress bar."
   echo "-M     Prints custom releasenote urls as markdown (requires template support)."
   echo "-n     No updates; only checking availability without interaction."