Added GRUB docs, Added netboot.xyz

boot/grub/persistent/docs/14_user_interface

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+14 GRUB's user interface
+************************
+
+GRUB has both a simple menu interface for choosing preset entries from a
+configuration file, and a highly flexible command-line for performing
+any desired combination of boot commands.
+
+   GRUB looks for its configuration file as soon as it is loaded.  If
+one is found, then the full menu interface is activated using whatever
+entries were found in the file.  If you choose the "command-line" menu
+option, or if the configuration file was not found, then GRUB drops to
+the command-line interface.
+
+14.1 The flexible command-line interface
+========================================
+
+The command-line interface provides a prompt and after it an editable
+text area much like a command-line in Unix or DOS. Each command is
+immediately executed after it is entered(1) (*note Command-line
+interface-Footnote-1::).  The commands (*note Command-line and menu
+entry commands::) are a subset of those available in the configuration
+file, used with exactly the same syntax.
+
+   Cursor movement and editing of the text on the line can be done via a
+subset of the functions available in the Bash shell:
+
+<C-f>
+<PC right key>
+     Move forward one character.
+
+<C-b>
+<PC left key>
+     Move back one character.
+
+<C-a>
+<HOME>
+     Move to the start of the line.
+
+<C-e>
+<END>
+     Move the the end of the line.
+
+<C-d>
+<DEL>
+     Delete the character underneath the cursor.
+
+<C-h>
+<BS>
+     Delete the character to the left of the cursor.
+
+<C-k>
+     Kill the text from the current cursor position to the end of the
+     line.
+
+<C-u>
+     Kill backward from the cursor to the beginning of the line.
+
+<C-y>
+     Yank the killed text back into the buffer at the cursor.
+
+<C-p>
+<PC up key>
+     Move up through the history list.
+
+<C-n>
+<PC down key>
+     Move down through the history list.
+
+   When typing commands interactively, if the cursor is within or before
+the first word in the command-line, pressing the <TAB> key (or <C-i>)
+will display a listing of the available commands, and if the cursor is
+after the first word, the '<TAB>' will provide a completion listing of
+disks, partitions, and file names depending on the context.  Note that
+to obtain a list of drives, one must open a parenthesis, as 'root ('.
+
+   Note that you cannot use the completion functionality in the TFTP
+filesystem.  This is because TFTP doesn't support file name listing for
+the security.
+
+   (1) However, this behavior will be changed in the future version, in
+a user-invisible way.
+
+14.2 The simple menu interface
+==============================
+
+The menu interface is quite easy to use.  Its commands are both
+reasonably intuitive and described on screen.
+
+   Basically, the menu interface provides a list of "boot entries" to
+the user to choose from.  Use the arrow keys to select the entry of
+choice, then press <RET> to run it.  An optional timeout is available to
+boot the default entry (the first one if not set), which is aborted by
+pressing any key.
+
+   Commands are available to enter a bare command-line by pressing <c>
+(which operates exactly like the non-config-file version of GRUB, but
+allows one to return to the menu if desired by pressing <ESC>) or to
+edit any of the "boot entries" by pressing <e>.
+
+   If you protect the menu interface with a password (*note Security::),
+all you can do is choose an entry by pressing <RET>, or press <p> to
+enter the password.
+
+14.3 Editing a menu entry
+=========================
+
+The menu entry editor looks much like the main menu interface, but the
+lines in the menu are individual commands in the selected entry instead
+of entry names.
+
+   If an <ESC> is pressed in the editor, it aborts all the changes made
+to the configuration entry and returns to the main menu interface.
+
+   Each line in the menu entry can be edited freely, and you can add new
+lines by pressing <RET> at the end of a line.  To boot the edited entry,
+press <Ctrl-x>.
+
+   Although GRUB unfortunately does not support "undo", you can do
+almost the same thing by just returning to the main menu using <ESC>.
+