From b66973344e3387f1a8450d091489a8a9671e8738 Mon Sep 17 00:00:00 2001
From: Matthew Brooks <address@hidden>
Date: Sun, 29 Mar 2020 14:55:34 -0500
Subject: [PATCH] Cookbook: Adding example of bind-mounting in the operating
 system definition.

---
 doc/guix-cookbook.texi | 46 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/doc/guix-cookbook.texi b/doc/guix-cookbook.texi
index 477b7e3dff..78b99abda8 100644
--- a/doc/guix-cookbook.texi
+++ b/doc/guix-cookbook.texi
@@ -1320,6 +1320,7 @@ reference.
 
 @menu
 * Customizing the Kernel::     Creating and using a custom Linux kernel on Guix System.
+* Bind-mounting file systems:: Setting up a bind-mount in the file-systems definition.
 @end menu
 
 @node Customizing the Kernel
@@ -1562,6 +1563,51 @@ likely that you'll need to modify the initrd on a machine using a custom
 kernel, since certain modules which are expected to be built may not be
 available for inclusion into the initrd.
 
+@c *********************************************************************
+@node Bind-mounting file-systems
+@section Bind-mounting file-systems
+
+To bind-mount a file-system, one must first set up some definitions before the @code{operating-system} section of the system definition. In this example we will bind-mount a folder from a spinning disk drive to @code{/tmp}, to save wear and tear on the primary
+SSD, without dedicating an entire partition to be mounted as @code{/tmp}.
+
+First, the source drive that hosts the folder we wish to bind mount should be defined, so that the bind-mount can depend on it.
+
+@lisp
+(define source-drive ;; "source-drive" can be named anything you want.
+   (file-system
+    (device (uuid "UUID goes here"))
+    (mount-point "/path-to-spinning-disk-goes-here")
+    (type "ext4"))) ;; Make sure to set this to the appropriate type for your drive.
+@end lisp
+
+The source folder must also be defined, so that guix will know it's not a regular block device, but a folder.
+@lisp
+(define (%source-directory) "/path-to-spinning-disk-goes-here/tmp") ;; "source-directory" can be named any valid variable name.
+@end lisp
+
+Finally, inside the @code{file-systems} definition, we must add the mount itself.
+
+@lisp
+(file-systems (cons*
+
+                ...<other drives omitted for clarity>...
+
+                source-drive ;; Must match the name you gave the source drive in the earlier definition.
+
+                (file-system
+                 (device (%source-directory)) ;; Make sure "source-directory" matches your earlier definition.
+                 (mount-point "/tmp")
+                 (type "none") ;; We are mounting a folder, not a partition, so this type needs to be "none"
+                 (flags '(bind-mount))
+                 (dependencies (list source-drive)) ;; Ensure "source-drive" matches what you've named the variable for the drive.
+                 )
+
+                 ...<other drives omitted for clarity>...
+
+                ))
+@end lisp
+
+
 @c *********************************************************************
 @node Advanced package management
 @chapter Advanced package management
-- 
2.25.1