Document the pull_options

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

docs/containers-storage.conf.5.md

@@ -41,7 +41,7 @@ The `storage` table supports the following options:
   When changing the graphroot location on an SELINUX system, ensure
   the labeling matches the default locations labels with the
   following commands:
-  
+
 ```
 # semanage fcontext -a -e /var/lib/containers/storage /NEWSTORAGEPATH
 # restorecon -R -v /NEWSTORAGEPATH
@@ -74,6 +74,33 @@ The `storage.options` table supports the following options:
 **additionalimagestores**=[]
   Paths to additional container image stores. Usually these are read/only and stored on remote network shares.
 
+**pull_options** = {enable_partial_images = "false", enable_host_deduplication = "false", use_hard_links = "false", ostree_repos=""}
+
+Allows specification of how storage is populated when pulling images. This
+option can speed the pulling process of images compressed with format zstd:chunked. Containers/storage looks
+for files within images that are being pulled from a container registry that
+were previously pulled to the host.  It can copy or create
+a hard link to the existing file when it finds them, eliminating the need to pull them from the
+container registry. These options can deduplicate pulling of content, disk
+storage of content and can allow the kernel to use less memory when running
+containers.
+
+containers/storage supports four keys
+  * enable_partial_images="true" | "false"
+    Tells containers/storage to look for files previously pulled in storage
+    rather then always pulling them from the container registry.
+  * use_hard_links = "false" | "true"
+    Tells containers/storage to use hard links rather then create new files in
+    the image, if an identical file already existed in storage.
+  * enable_host_deduplication = "false" | "true"
+    Tells containers/storage to search for files under `/usr` in addition to
+    files in other images when attempting to avoid pulling files from the
+    container registry.
+  * ostree_repos = ""
+    Tells containers/storage where an ostree repository exists that might have
+    previously pulled content which can be used when attempting to avoid
+    pulling content from the container registry
+
 **remap-uids=**""
 **remap-gids=**""
   Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of a container, to the UIDs/GIDs outside of the container, and the length of the range of UIDs/GIDs.  Additional mapped sets can be listed and will be heeded by libraries, but there are limits to the number of mappings which the kernel will allow when you later attempt to run a container.

storage.conf

@@ -40,6 +40,32 @@ graphroot = "/var/lib/containers/storage"
 additionalimagestores = [
 ]
 
+# Allows specification of how storage is populated when pulling images. This
+# option can speed the pulling process of images compressed with format
+# zstd:chunked. Containers/storage looks for files within images that are being
+# pulled from a container registry that were previously pulled to the host.  It
+# can copy or create a hard link to the existing file when it finds them,
+# eliminating the need to pull them from the container registry. These options
+# can deduplicate pulling of content, disk storage of content and can allow the
+# kernel to use less memory when running containers.
+
+# containers/storage supports four keys
+#   * enable_partial_images="true" | "false"
+#     Tells containers/storage to look for files previously pulled in storage
+#     rather then always pulling them from the container registry.
+#   * use_hard_links = "false" | "true"
+#     Tells containers/storage to use hard links rather then create new files in
+#     the image, if an identical file already existed in storage.
+#   * enable_host_deduplication = "false" | "true"
+#     Tells containers/storage to search for files under `/usr` in addition to
+#     files in other images when attempting to avoid pulling files from the
+#     container registry.
+#   * ostree_repos = ""
+#     Tells containers/storage where an ostree repository exists that might have
+#     previously pulled content which can be used when attempting to avoid
+#     pulling content from the container registry
+pull_options = {enable_partial_images = "false", enable_host_deduplication = "false", use_hard_links = "false", ostree_repos=""}
+
 # Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of
 # a container, to the UIDs/GIDs as they should appear outside of the container,
 # and the length of the range of UIDs/GIDs.  Additional mapped sets can be