grub2: Serial terminal
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1 9 Using GRUB via a serial line
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1 This chapter describes how to use the serial terminal support in GRUB.
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1 If you have many computers or computers with no display/keyboard, it
1 could be very useful to control the computers through serial
1 communications. To connect one computer with another via a serial line,
1 you need to prepare a null-modem (cross) serial cable, and you may need
1 to have multiport serial boards, if your computer doesn't have extra
1 serial ports. In addition, a terminal emulator is also required, such
1 as minicom. Refer to a manual of your operating system, for more
1 information.
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1 As for GRUB, the instruction to set up a serial terminal is quite
1 simple. Here is an example:
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1 grub> serial --unit=0 --speed=9600
1 grub> terminal_input serial; terminal_output serial
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1 The command 'serial' initializes the serial unit 0 with the speed
1 9600bps. The serial unit 0 is usually called 'COM1', so, if you want to
1 use COM2, you must specify '--unit=1' instead. This command accepts
1 many other options, so please refer to ⇒serial, for more details.
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1 The commands 'terminal_input' (⇒terminal_input) and
1 'terminal_output' (⇒terminal_output) choose which type of
1 terminal you want to use. In the case above, the terminal will be a
1 serial terminal, but you can also pass 'console' to the command, as
1 'terminal_input serial console'. In this case, a terminal in which you
1 press any key will be selected as a GRUB terminal. In the example
1 above, note that you need to put both commands on the same command line,
1 as you will lose the ability to type commands on the console after the
1 first command.
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1 However, note that GRUB assumes that your terminal emulator is
1 compatible with VT100 by default. This is true for most terminal
1 emulators nowadays, but you should pass the option '--dumb' to the
1 command if your terminal emulator is not VT100-compatible or implements
1 few VT100 escape sequences. If you specify this option then GRUB
1 provides you with an alternative menu interface, because the normal menu
1 requires several fancy features of your terminal.
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