Add some information about disabling SELinux when using system volumes

A comment was made on internal mailing list about confusion on SELinux
labeling of volumes. This PR makes it a little more clear about when
you should or should not relabel.

We need a similar comment in podman pod create, but it does not support
--security-opt processing yet.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/docs/source/markdown/podman-build.1.md b/docs/source/markdown/podman-build.1.md
index 5a867c574..835df7693 100644
--- a/docs/source/markdown/podman-build.1.md
+++ b/docs/source/markdown/podman-build.1.md
@@ -774,6 +774,14 @@ content label. Shared volume labels allow all containers to read/write content.
 The `Z` option tells Podman to label the content with a private unshared label.
 Only the current container can use a private volume.
 
+Note: Do not relabel system files and directories. Relabeling system content
+might cause other confined services on your machine to fail.  For these types
+of containers, disabling SELinux separation is recommended.  The option
+`--security-opt label=disable` disables SELinux separation for the container.
+For example, if a user wanted to volume mount their entire home directory into the build containers, they need to disable SELinux separation.
+
+	   $ podman build --security-opt label=disable -v $HOME:/home/user .
+
   `Overlay Volume Mounts`
 
    The `:O` flag tells Podman to mount the directory from the host as a