Docu update

doc/yupdate.md

@@ -51,12 +51,12 @@ This script is intended to help in the following scenarios.
 
 ### Make the inst-sys Writable
 
-As already mentioned, the files in the installation system are compressed and
-and marked as read only. To be able to patch the installer the script must be
-able to make the files writable. It does that automatically for the updated files,
-but maybe you would like to use this feature for some other files.
+As already mentioned, the files in the installation system are read only. To be
+able to patch the installer the script must be able to make the files writable.
+It does that automatically for the updated files, but maybe you would like to
+use this feature also for some other non-YaST files.
 
-To make a directory in the inst-sys writable run command
+To make a directory writable in the inst-sys run command
 
 ```shell
 yupdate overlay create <dir>
@@ -66,11 +66,13 @@ This will create a writable overlay above the specified directory. If you do not
 specify any directory it will create writable overlays for the default YaST directories.
 
 Then you can easily edit the files using the included `vim` editor
-or by other tools like `sed`.
+or by other tools like `sed` or overwrite by external files.
 
 ### Patch YaST from GitHub Sources
 
-To install an YaST package directly from the GitHub repository use command
+To update or install an YaST package directly from the GitHub source code repository
+use command
+
 ```shell
 yupdate patch <github_slug> <branch>
 ```
@@ -109,7 +111,7 @@ In that case run
 rake server
 ```
 
-in your Git checkout, which will run a web server providing source tarball
+in your YaST module Git checkout. This will run a web server providing source tarball
 similar to the GitHub archive used in the previous case.
 
 *Note: You need "yast-rake" Ruby gem version 0.2.37 or newer.*
@@ -120,12 +122,17 @@ Then run
 yupdate patch <host_name>
 ```
 
-where `<host_name>`  is the machine host name or the IP address. To make it easier
-the rake task prints these values at the start.
+where `<host_name>`  is the machine host name or the IP address where you run
+the `rake server` task. To make it easier the rake task prints these values at
+the start.
 
 By default this will use port 8000, if the server uses another port just add
 `:` followed by the port number.
 
+*Note: Make sure the server port is open in the firewall configuration,
+see the [documentation](https://github.com/yast/yast-rake/#server) for
+more details.*
+
 #### Patching Multiple Packages
 
 The `yast patch` command installs the sources from all running `rake server`
@@ -209,7 +216,7 @@ state.
 ### OverlayFS
 
 To make the inst-sys directories writable we use the Linux OverlayFS
-which can merge already existing filesystems ("union filesystem").
+which can merge already existing file systems ("union filesystem").
 
 See more details in the [Linux Kernel Documentation](
 https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt).
@@ -218,11 +225,11 @@ https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt).
 
 For installing the sources the script uses the `rake install DESTDIR=...`
 command and install the files into a temporary directory. Then it compares
-the new files with the original files and if there is a change the new
-file copied to the original place.
+the new files with the original files and if there is a change the old
+file is rewritten by the new file.
 
-This also skips some not really needed files like documentation, manual pages,
-editor backup file,...
+This also skips some not needed files like documentation, manual pages,
+editor backup files, etc...
 
-This saves some memory as we do not need to shadow the unused files
-or files with the same content.
+This saves some memory as we do not need to shadow the not modified files
+with the same content.