Boot loader ref file changes

guides/common/assembly_bootloader-binary-location.adoc

@@ -8,4 +8,6 @@ include::modules/ref_pxelinux-bootloaders.adoc[leveloffset=+1]
 
 include::modules/ref_grub2-uefi-bootloaders.adoc[leveloffset=+1]
 
-include::modules/ref_ipxe-bootloaders.adoc[leveloffset=+1]
+include::modules/ref_http-bootloaders.adoc[leveloffset=+1]
+
+include::modules/ref_shared-tftp-http-root.adoc[leveloffset=+1]

guides/common/modules/ref_http-bootloaders.adoc

@@ -0,0 +1,36 @@
+:_mod-docs-content-type: REFERENCE
+
+[id="ref_http-bootloaders_{context}"]
+= HTTP-based boot loaders
+
+[role="_abstract"]
+In addition to the *TFTP-based PXE* mechanism, {Project} supports boot methods that use *HTTP*.
+HTTP-based boot methods use the {SmartProxy}’s *HTTPBoot* module to deliver bootloaders and installation files.
+HTTP-based boot methods in {Project} are *iPXE*, *iPXE chainloading*, and *Grub2 UEFI HTTP Boot*.
+Each method offers advantages depending on the firmware type and network environment.
+
+The *HTTPBoot* feature exposes the same files that are available via TFTP, but over the HTTP or HTTPS protocol.
+This can improve boot reliability in environments where TFTP is blocked, unreliable, or slow.
+
+The boot methods in {Project} use the following boot workflows:
+
+iPXE chainloading (PXE to HTTP)::
+
+The boot process starts with a traditional PXE (TFTP) stage and then switches to HTTP for improved performance and flexibility.
+With this hybrid approach, existing PXE infrastructure can use HTTP for the later boot stages without requiring firmware-level HTTP support.
++
+iPXE chainloading uses the following workflow:
++
+. The firmware downloads the appropriate iPXE loader via TFTP.
+  * BIOS downloads `undionly-ipxe.0`.
+  * UEFI downloads `ipxe.efi`.
+. iPXE initializes the network and switches to HTTP, requesting an iPXE script such as `menu.ipxe`.
+
+iPXE and Grub2 UEFI HTTP(S) boot::
+
+UEFI firmware directly loads boot loaders by using HTTP or HTTPS without any TFTP step.
++
+iPXE and Grub2 UEFI HTTP(S) Boot use the following workflow:
++
+. UEFI firmware requests boot loader files from the {SmartProxy} via HTTP or HTTPS, for example, `ipxe-__<arch>__.efi`.
+. Grub2 loads `grub.cfg` and starts the OS installer.

guides/common/modules/ref_shared-tftp-http-root.adoc

@@ -0,0 +1,68 @@
+:_mod-docs-content-type: REFERENCE
+
+[id="ref_shared-tftp-http-root_{context}"]
+= Shared TFTP and HTTP root
+
+[role="_abstract"]
+The {SmartProxy}’s *HTTPBoot* module and *TFTP* service share the same root directory. 
+By default, this directory is `/var/lib/tftpboot/`.
+
+[subs="+quotes"]
+----
+URL path:   http://_My_Smartproxy_Example.com_/httpboot/
+Filesystem: /var/lib/tftpboot/
+----
+
+This mapping means that the `/httpboot/` HTTP URL path directly corresponds to the local filesystem under `/var/lib/tftpboot/`.
+For example, a file located at `/var/lib/tftpboot/pxegrub2/grubx64.efi` is available over HTTP at `http://_My_Smartproxy_Example.com_/httpboot/pxegrub2/grubx64.efi`.
+
+This shared structure simplifies management by ensuring that both PXE (TFTP) and HTTP clients use the same set of boot loader binaries and configuration files.
+
+.Model iPXE and HTTPBoot-related directory layout
+====
+----
+# tree /var/lib/tftpboot/
+/var/lib/tftpboot/
+ ├── undionly-ipxe.0
+ ├── ipxe.efi
+ ├── ipxe-x64.efi
+ └── grub2/
+      ├── grubx64.efi
+      └── shimx64.efi
+----
+====
+
+.Default boot loader files
+
+[cols="1,1", options="header"]
+|===
+| Default path
+| Purpose
+
+| `/var/lib/tftpboot/undionly-ipxe.0`
+| iPXE boot loader for **iPXE Chain BIOS**.
+Used in BIOS environments as the first-stage loader that transitions from TFTP-based PXE to HTTP-based iPXE boot.
+
+| `/var/lib/tftpboot/ipxe.efi`
+| iPXE boot loader for **iPXE Chain UEFI**.
+Used in UEFI environments to chainload into iPXE for HTTP-based provisioning.
+
+| `/var/lib/tftpboot/ipxe-x64.efi`
+| Architecture-specific iPXE binary for **iPXE UEFI HTTP** boot.
+Used for direct iPXE boot via HTTP without TFTP chainloading.
+
+| `/var/lib/tftpboot/grub2/grubx64.efi`
+| Grub2 UEFI boot loader for **Grub2 UEFI HTTP** or **HTTPS Boot**.
+Used to start UEFI installations via the {SmartProxy}’s HTTPBoot module.
+
+| `/var/lib/tftpboot/grub2/shimx64.efi`
+| Secure Boot shim loader for Grub2.
+Used when **Grub2 UEFI SecureBoot** or **Grub2 UEFI HTTPS SecureBoot** is selected.
+|===
+
+[NOTE]
+====
+Grub2 UEFI HTTPS Boot relies on the {SmartProxy}’s HTTPS service to securely deliver the `boot.efi`, `shimx64.efi`, and similar boot loader binaries to UEFI clients. 
+The configuration for this HTTPS service is defined in the {SmartProxy}’s main settings file 
+`/etc/foreman-proxy/settings.yml`.
+====