From 00588180eea2ae621865ede52b7b9c619848c276 Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Sat, 1 Oct 2022 15:14:22 +0800
Subject: kernfs: modernize the explanation for bind mounting /dev

If you are using a "modern" distro (with devtmpfs and a modern udev
implementation), a bind mounting is actually not needed because you can
mount devtmpfs anyway.  The only reason for bind mounting is to be
compatible with old host distros where /dev is a directory containing
many static device nodes, or is a tmpfs (not same as devtmpfs) popluated
by bootscript or an old udev (modern udev implementations, including
eudev and systemd-udev used by LFS, strictly requires a devtmpfs on
/dev).

So update the explanation to match the status quo.
---
 chapter07/kernfs.xml | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

(limited to 'chapter07/kernfs.xml')

diff --git a/chapter07/kernfs.xml b/chapter07/kernfs.xml
index 54b864130..4a1cac179 100644
--- a/chapter07/kernfs.xml
+++ b/chapter07/kernfs.xml
@@ -29,16 +29,27 @@
   <sect2 id="ch-tools-bindmount">
     <title>Mounting and Populating /dev</title>
 
-      <para>During a normal boot, the kernel automatically mounts the
-      <systemitem class="filesystem">devtmpfs</systemitem> filesystem on the
-      <filename class="directory">/dev</filename> directory; the
-      devices are created dynamically on that virtual filesystem when they
-      are first detected or accessed. Device creation is generally done during the
-      boot process by the kernel and the udev program.
-      Since the new system does not yet include udev and
-      has not yet been booted, it is necessary to mount and populate
-      the <filename class="directory">/dev</filename> directory manually. This is
-      accomplished by bind mounting the host system's
+      <para>During a normal boot of the LFS system, the kernel automatically
+      mounts the <systemitem class="filesystem">devtmpfs</systemitem>
+      filesystem on the
+      <filename class="directory">/dev</filename> directory; the kernel
+      creates device on that virtual filesystem during the boot process
+      or when a device is first detected or accessed. The udev daemon may
+      change the owner or permission of the device nodes created by the
+      kernel, or create new device nodes or symlinks to ease the work of
+      distro maintainers or system administrators.  (See
+      <xref linkend='ch-config-udev-device-node-creation'/> for details.)
+      If the host kernel supports &devtmpfs;, we can simply mount a
+      &devtmpfs; at <filename class='directory'>$LFS/dev</filename> and rely
+      on the kernel to populate it (the LFS building process does not need
+      the additional work onto &devtmpfs; by udev daemon).</para>
+
+      <para>But, some host kernels may lack &devtmpfs; support and these
+      host distros maintain the content of
+      <filename class="directory">/dev</filename> with different methods.
+      So the only host-agnostic way for populating
+      <filename class="directory">$LFS/dev</filename> is
+      bind mounting the host system's
       <filename class="directory">/dev</filename> directory. A bind mount is
       a special type of mount that allows you to create a mirror of a
       directory or mount point at some other location. Use the following
-- 
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