Changeset 96323bd for chapter07/kernfs.xml

Timestamp:

10/02/2022 01:49:39 PM (19 months ago)

Author:

Xi Ruoyao <xry111@…>

Branches:

xry111/arm64, xry111/arm64-12.0

Children:

1dcfd50

Parents:

111194c (diff), 6582ddc5 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge remote-tracking branch 'origin/trunk' into xry111/arm64

File:

• chapter07/kernfs.xml (modified) (3 diffs)

chapter07/kernfs.xml

@@ -15 +15 @@
   </indexterm>
 
-    <para>Various file systems exported by the kernel are used to communicate to
-    and from the kernel itself. These file systems are virtual in that no disk
+    <para>Applications running in user space utilize various file 
+    systems exported by the kernel to communicate 
+    with the kernel itself. These file systems are virtual: no disk
     space is used for them. The content of the file systems resides in
-    memory.</para>
+    memory. These file systems must be mounted in the $LFS directory tree
+    so the applications can find them in the chroot environment.</para>
 
-    <para>Begin by creating directories onto which the file systems will be
+    <para>Begin by creating directories on which the file systems will be
     mounted:</para>
 
@@ -28 +30 @@
     <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, and allow the
-      devices to be created dynamically on that virtual filesystem as they
-      are detected or accessed. Device creation is generally done during the
-      boot process by the kernel and Udev.
-      Since this new system does not yet have Udev and
-      has not yet been booted, it is necessary to mount and populate
-      <filename class="directory">/dev</filename> 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 nodes 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 to some other location. Use the following
-      command to achieve this:</para>
+      directory or mount point at some other location. Use the following
+      command to do this:</para>
 
 <screen><userinput>mount -v --bind /dev $LFS/dev</userinput></screen>
@@ -90 +103 @@
       directory needs to be created.</para>
 
-      <para>In other cases <filename>/dev/shm</filename> is a mountpoint 
+      <para>In other host systems <filename>/dev/shm</filename> is a mount point 
       for a tmpfs. In that case the mount of /dev above will only create
-      /dev/shm in the chroot environment as a directory. In this situation
-      we explicitly mount a tmpfs,</para>
+      /dev/shm as a directory in the chroot environment. In this situation
+      we must explicitly mount a tmpfs:</para>
 
 <screen><userinput>if [ -h $LFS/dev/shm ]; then