Add tip for symlinking ISO image (#3847)

I ran into difficulties with mounting the Ubuntu ISO image under
`/var/lib/foreman` since I manage foreman with puppet, and mounting the
ISO is more doable with puppet compared with copying the content. This
commit just adds a note for other people who might want to try the same
thing. This note may help someone avoid this particular pitfall.

Co-authored-by: Brian Angelica <[email protected]>
Co-authored-by: Lena Ansorgová <[email protected]>

Author: 3 people

guides/common/modules/proc_creating-an-installation-medium-for-ubuntu-22-04.adoc

@@ -43,5 +43,15 @@ Ensure the path in `/pub/` matches the path in your _Preseed default PXELinux Au
 # rm -f {iso_image}
 ----
 
+[TIP]
+====
+If you manage this with Puppet or a similar configuration management system, you can take an alternative approach.
+Instead of copying the ISO image content, you can create a symbolic link at `/var/www/html/pub/installation_media/ubuntu/22.04-x86_64` that points to the mounted image.
+Keep the ISO image mounted so that it is accessible to HTTP clients.
+
+Do not mount the ISO image directly under `/var/lib/foreman`.
+On Debian and Ubuntu, mounting under this directory causes the package `postinst` script to fail during the `chmod -Rf /var/lib/foreman` command.
+====
+
 Use `\http://{foreman-example-com}/pub/installation_media/ubuntu/22.04-x86_64/` to set up your installation media entry in {Project}.
 For more information, see xref:adding-installation-media_{context}[].