After all changes are made, the b key executes the commands and boots the operatingsystem. The Esc key discards any changes and reloads the standard menu interface. The ckey loads the command line interface.TipFor information about changing runlevels using the GRUB menu entry editor,refer to Section 8, “Changing Runlevels at Boot Time”.Command Line InterfaceThe command line interface is the most basic GRUB interface, but it is also the one thatgrants the most control. The command line makes it possible to type any relevant GRUBcommands followed by the Enter key to execute them. This interface features someadvanced shell-like features, including Tab key completion, based on context, and Ctrl keycombinations when typing commands, such as Ctrl-a to move to the beginning of a line andCtrl-e to move to the end of a line. In addition, the arrow, Home, End, and Delete keyswork as they do in the bash shell.Refer to Section 6, “GRUB Commands” for a list of common commands.5.1. Interfaces Load OrderWhen GRUB loads its second stage boot loader, it first searches for its configuration file. Oncefound, the menu interface bypass screen is displayed. If a key is pressed within three seconds,GRUB builds a menu list and displays the menu interface. If no key is pressed, the defaultkernel entry in the GRUB menu is used.If the configuration file cannot be found, or if the configuration file is unreadable, GRUB loadsthe command line interface, allowing the user to type commands to complete the boot process.If the configuration file is not valid, GRUB prints out the error and asks for input. This helps theuser see precisely where the problem occurred. Pressing any key reloads the menu interface,where it is then possible to edit the menu option and correct the problem based on the errorreported by GRUB. If the correction fails, GRUB reports an error and reloads the menuinterface.6. GRUB CommandsGRUB allows a number of useful commands in its command line interface. Some of thecommands accept options after their name; these options should be separated from thecommand and other options on that line by space characters.The following is a list of useful commands:Interfaces Load Order19
