Add initcpio instructions for 9p boot

docs/linux-9p-image.md

@@ -12,3 +12,47 @@ CONFIG_9P_FS_POSIX_ACL=y
 ```
 
 A Dockerfile for this build is here: https://github.com/ysangkok/build-v86-9p-linux
+
+Using initcpio
+--------------
+
+This allows you to remount the root file system using 9p. No changes are necessary if you only want to mount a 9p filesystem after booting.
+
+Add the following files:
+
+`/etc/initcpio/hooks/9p_root`
+
+```bash
+#!/usr/bin/bash
+
+run_hook() {
+    mount_handler="mount_9p_root"
+}
+
+mount_9p_root() {
+    msg ":: mounting '$root' on real root (9p)"
+    if ! mount -t 9p "$root" "$1"; then
+        echo "You are now being dropped into an emergency shell."
+        launch_interactive_shell
+        msg "Trying to continue (this will most likely fail) ..."
+    fi
+}
+```
+
+<hr>
+
+`/etc/initcpio/install/9p_root`
+
+```bash
+#!/bin/bash
+build() {
+	add_runscript
+}
+```
+
+Change the following options in `/etc/mkinitcpio.conf`:
+
+```bash
+MODULES="virtio_pci 9p 9pnet 9pnet_virtio"
+HOOKS="base udev autodetect modconf block filesystems keyboard fsck 9p_root" # appended 9p_root
+```