fixup! docs(netboot): add full netboot setup guide

Author: iav

extensions/netboot/README.md

@@ -272,28 +272,44 @@ When the machine building the image is also the NFS server for the
 target, you can skip the archive entirely: build straight into the
 export directory.
 
+One-time setup: if the builder is also the NFS server and you want
+exports to live directly under `/srv/netboot/rootfs/`, symlink
+`${SRC}/output/netboot-export` to that root:
+
+```sh
+ln -s /srv/netboot/rootfs ${SRC}/output/netboot-export
+```
+
+Then the `ROOTFS_EXPORT_DIR` values below resolve straight into the
+NFS tree. Without the symlink everything still works, just the
+artefacts sit under `${SRC}/output/netboot-export/` and you rsync them
+out later.
+
 ```sh
 ./compile.sh build \
-  BOARD=helios64 BRANCH=edge RELEASE=resolute \
+  BOARD=helios64 BRANCH=edge RELEASE=trixie \
   BUILD_MINIMAL=yes \
   ROOTFS_TYPE=nfs-root \
   NETBOOT_SERVER=192.168.1.125 \
   NETBOOT_HOSTNAME=helios64-a \
   NETBOOT_CLIENT_MAC=aa:bb:cc:dd:ee:ff \
   ROOTFS_COMPRESSION=none \
-  ROOTFS_EXPORT_DIR=/srv/netboot/rootfs/hosts/helios64-a
+  ROOTFS_EXPORT_DIR=hosts/helios64-a
 ```
 
 What happens:
 
 - `ROOTFS_COMPRESSION=none` skips the tar/gzip step. No `*.tar.gz`
   appears under `output/images/`.
-- `ROOTFS_EXPORT_DIR` is populated via `rsync -aHWh`, preserving
-  permissions, xattrs, hardlinks.
-- Because the path is outside `${SRC}`, the extension bind-mounts it
-  into the build container via
-  `host_pre_docker_launch__netboot_mount_export_dir` — the same build
-  command works on bare-metal and in Docker.
+- `ROOTFS_EXPORT_DIR=hosts/helios64-a` expands to
+  `${SRC}/output/netboot-export/hosts/helios64-a` on the host side;
+  `rsync -aHWh` populates it with the rootfs tree (permissions,
+  xattrs, hardlinks preserved).
+- In Docker builds the extension bind-mounts that host path onto a
+  fixed container target (`/armbian/netboot-export`) and points
+  `ROOTFS_EXPORT_DIR` there, so rsync inside the container can never
+  escape the netboot-export subtree. Same build command works in
+  native builds — just no docker hop.
 - `pre_umount_final_image__900_collect_netboot_artifacts` still
   produces the TFTP tree at
   `${FINALDEST}/<version>-netboot-tftp/armbian/<family>/<board>/<branch>-<release>/`
@@ -409,7 +425,7 @@ the image a unique set of SSH host keys per boot.
 
 ## End-to-end example: helios64
 
-Target: Helios64 (`rockchip64/helios64`, `edge`/`resolute`,
+Target: Helios64 (`rockchip64/helios64`, `edge`/`trixie`,
 `ttyS2@1500000`). Builder and NFS server are the same Linux host at
 `192.168.1.125`, reachable as `m1`. DHCP is OpenWRT at `192.168.1.1`.
 
@@ -446,22 +462,25 @@ ssh root@192.168.1.1 \
 ### 3. Build (single-step, builder = NFS server)
 
 ```sh
+# One-time on the builder (already the NFS server here):
+ln -s /srv/netboot/rootfs ${SRC}/output/netboot-export
+
 ./compile.sh build \
-  BOARD=helios64 BRANCH=edge RELEASE=resolute \
+  BOARD=helios64 BRANCH=edge RELEASE=trixie \
   BUILD_MINIMAL=yes \
   ROOTFS_TYPE=nfs-root \
   NETBOOT_SERVER=192.168.1.125 \
   ROOTFS_COMPRESSION=none \
-  ROOTFS_EXPORT_DIR=/srv/netboot/rootfs/shared/rockchip64/helios64/edge-resolute
+  ROOTFS_EXPORT_DIR=shared/rockchip64/helios64/edge-trixie
 ```
 
 ### 4. Drop the TFTP tree into place
 
 ```sh
 rsync -a output/images/*-netboot-tftp/ /srv/netboot/tftp/
 # -> /srv/netboot/tftp/pxelinux.cfg/default.example
-# -> /srv/netboot/tftp/armbian/rockchip64/helios64/edge-resolute/Image
-# -> /srv/netboot/tftp/armbian/rockchip64/helios64/edge-resolute/dtb/rockchip/...
+# -> /srv/netboot/tftp/armbian/rockchip64/helios64/edge-trixie/Image
+# -> /srv/netboot/tftp/armbian/rockchip64/helios64/edge-trixie/dtb/rockchip/...
 mv /srv/netboot/tftp/pxelinux.cfg/default.example \
    /srv/netboot/tftp/pxelinux.cfg/default
 ```
@@ -485,8 +504,8 @@ Scanning bootdev 'ethernet@fe300000.bootdev':
   Retrieving file: pxelinux.cfg/<hex-ip>
   Retrieving file: pxelinux.cfg/default
   Config file 'pxelinux.cfg/default' found
-  Retrieving file: armbian/rockchip64/helios64/edge-resolute/Image
-  Retrieving file: armbian/rockchip64/helios64/edge-resolute/dtb/rockchip/rk3399-kobol-helios64.dtb
+  Retrieving file: armbian/rockchip64/helios64/edge-trixie/Image
+  Retrieving file: armbian/rockchip64/helios64/edge-trixie/dtb/rockchip/rk3399-kobol-helios64.dtb
   append: root=/dev/nfs nfsroot=192.168.1.125:/srv/netboot/rootfs/shared/...,tcp,v3 ip=dhcp rw rootwait earlycon loglevel=7 panic=10
   Starting kernel ...
 ...