Update text in Chapter 7 Backup/Restore sections

Patch by Kevin Buckley.
Also made minor clarification to umount commands.

chapter01/changelog.xml

@@ -43,6 +43,16 @@
     appropriate for the entry or if needed the entire day's listitem.
     -->
 
+    <listitem>
+      <para>2021-09-06</para>
+      <itemizedlist>
+        <listitem>
+          <para>[bdubbs] - Text clarifications in the backup/restore section
+          o fChapter 7. Thanks to Kevin Buckley for the patch.</para>
+        </listitem>
+      </itemizedlist>
+    </listitem>
+
     <listitem>
       <para>2021-09-01</para>
       <itemizedlist>

chapter07/cleanup.xml

@@ -20,7 +20,7 @@
 
     <para>Second, the libtool .la files are only useful when linking with static
     libraries. They are unneeded and potentially harmful when using dynamic
-    shared libraries, specially when using non-autotools build systems.
+    shared libraries, especially when using non-autotools build systems.
     While still in chroot, remove those files now:</para>
 
 <screen><userinput>find /usr/{lib,libexec} -name \*.la -delete</userinput></screen>
@@ -37,6 +37,17 @@
   <sect2>
     <title>Backup</title>
 
+    <para>
+      At this point the essential programs and libraries have been created
+      and your current LFS system is in a good state. Your system can now be
+      backed up for later reuse. In case of fatal failures in the subsequent
+      chapters, it often turns out that removing everything and starting over
+      (more carefully) is the best option to recover. Unfortunately, all the
+      temporary files will be removed, too. To avoid spending extra time to
+      redo something which has been built successfully, creating a backup of
+      the current LFS system may prove useful.
+    </para>
+
     <note><para>
       All the remaining steps in this section are optional. Nevertheless,
       as soon as you begin installing packages in <xref
@@ -56,47 +67,54 @@
       safety reasons.
     </para>
 
-    <important>
-      <para>All of the following instructions are executed by
-        <systemitem class="username">root</systemitem>. Take extra
-        care about the commands you're going to run as mistakes
-        here can modify your host system. Be aware that the
-        environment variable <envar>LFS</envar> 
-        is set for user <systemitem class="username">lfs</systemitem> by default 
-        but may <emphasis>not</emphasis> be set for 
-        <systemitem class="username">root</systemitem>. Whenever 
-        commands are to be executed by <systemitem class="username">root</systemitem>, 
-        make sure you have set <envar>LFS</envar>.
-        This has been discussed in <xref linkend='ch-partitioning-aboutlfs'/>.
-      </para>
-    </important>
-
     <para>
-       Now, if you are making a backup, leave the chroot environment:
+       If you have decided to make a backup, leave the chroot environment:
     </para>
 
 <screen role="nodump"><userinput>exit</userinput></screen>
 
+    <important>
       <para>
-      At this point the essential programs and libraries have been created
+        All of the following instructions are executed by
-      and your current system is in a good state. Your system can now be
+        <systemitem class="username">root</systemitem> on your host system.
-      backed up for later reuse. In case of fatal failures in the subsequent
+        Take extra care about the commands you're going to run as mistakes
-      chapters, it often turns out that removing everything and starting over
+        here can modify your host system. Be aware that the
-      (more carefully) is the best option to recover. Unfortunately, all the
+        environment variable <envar>LFS</envar> 
-      temporary files will be removed, too. To avoid spending extra time to
+        is set for user <systemitem class="username">lfs</systemitem> by default 
-      redo something which has been built successfully, prepare a backup.
+        but may <emphasis>not</emphasis> be set for 
+        <systemitem class="username">root</systemitem>.
      </para>
+     <para>
+        Whenever commands are to be executed by <systemitem class="username">root</systemitem>, 
+        make sure you have set <envar>LFS</envar>.
+     </para>
+     <para>
+        This has been discussed in <xref linkend='ch-partitioning-aboutlfs'/>.
+      </para>
+    </important>
+
+    <para>Before making a backup, unmount the virtual file systems:</para>
+
+<screen role="nodump"><userinput>umount $LFS/dev/pts
+umount $LFS/{sys,proc,run,dev}</userinput></screen>
 
     <para>
       Make sure you have at least 1 GB free disk space (the source tarballs
-      will be included in the backup archive) in the home directory of user 
+      will be included in the backup archive) on the filesystem containing
-      <systemitem class="username">root</systemitem>.
+      directory where you create the backup archive.
     </para>
 
-    <para>Before we make a backup, unmount the virtual file systems:</para>
+    <para>
+      Note that the instructions below specify the home directory of the host
+      system's <systemitem class="username">root</systemitem> user, which is
+      typically found on the root filesystem.
+    </para>
 
-<screen role="nodump"><userinput>umount $LFS/dev{/pts,}
+    <para>
-umount $LFS/{sys,proc,run}</userinput></screen>
+      Replace <envar>$HOME</envar> by a directory of your choice if you
+      do not want to have the backup stored in <systemitem 
+      class="username">root</systemitem>'s home directory.
+    </para>
 
     <para>
       Create the backup archive by running the following command:
@@ -107,11 +125,6 @@ umount $LFS/{sys,proc,run}</userinput></screen>
           Because the backup archive is compressed, it takes a relatively
           long time (over 10 minutes) even on a resonably fast system.
        </para>
-       
-       <para>
-          Also, ensure the <envar>LFS</envar> environment variable is set 
-          for the root user.
-       </para>
     </note>
 
 <screen role="nodump" revision="sysv"><userinput>cd $LFS 
@@ -120,11 +133,6 @@ tar -cJpf $HOME/lfs-temp-tools-&version;.tar.xz .</userinput></screen>
 <screen role="nodump" revision="systemd"><userinput>cd $LFS 
 tar -cJpf $HOME/lfs-temp-tools-&versiond;.tar.xz .</userinput></screen>
 
-    <para>
-      Replace <envar>$HOME</envar> by a directory of your choice if you
-      do not want to have the backup stored in <systemitem 
-      class="username">root</systemitem>'s home directory.
-    </para>
   </sect2>
 
   <sect2>