Update documentation of podman-run to reflect volume "U" option

The "U" option is accepted by `--volume` in `podman-build`,
but documentation is missing

Signed-off-by: Pablo Correa Gómez <ablocorrea@hotmail.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/docs/source/markdown/podman-build.1.md b/docs/source/markdown/podman-build.1.md
index a91c7b6a6..876bfe412 100644
--- a/docs/source/markdown/podman-build.1.md
+++ b/docs/source/markdown/podman-build.1.md
@@ -692,6 +692,7 @@ Set the architecture variant of the image to be pulled.
 
    * [rw|ro]
    * [z|Z|O]
+   * [U]
    * [`[r]shared`|`[r]slave`|`[r]private`]
 
 The `CONTAINER-DIR` must be an absolute path such as `/src/docs`. The `HOST-DIR`
@@ -707,6 +708,18 @@ You can add the `:ro` or `:rw` suffix to a volume to mount it read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 See examples.
 
+  `Chowning Volume Mounts`
+
+By default, Podman does not change the owner and group of source volume
+directories mounted. When running using user namespaces, the UID and GID inside
+the namespace may correspond to another UID and GID on the host.
+
+The `:U` suffix tells Podman to use the correct host UID and GID based on the
+UID and GID within the namespace, to change recursively the owner and group of
+the source volume.
+
+**Warning** use with caution since this will modify the host filesystem.
+
   `Labeling Volume Mounts`
 
 Labeling systems like SELinux require that proper labels are placed on volume