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I'm currently using a laptop with a missing screen, so I've connected an external monitor which, for the most part, has worked quite well.

Problems arise, however, if I have multiple Linux distros installed, for example. Normally, with multiple distros installed, a boot menu quickly appears after start up, prompting the user to select the one they wish to load. Without a 'native' laptop screen, while connected to an external monitor, this boot menu never appears. To be more precise, the boot menu loads (of course), but it never appears on the external monitor.

This is also a problem when installing a new distro, I've found.

My solution is to remove the hard drive and temporarily connect it in another machine with a working screen, install linux, and move it back.

My question is: Is there a way to force screen output to an external monitor before linux loads (during the OS selection menu or while installing a new OS), or does a simpler solution jump out at you that I have missed?

[Edited to include BIOS information]

BIOS Information
        Vendor: LENOVO
        Version: H0ET32WW (1.14 )
        Release Date: 06/15/2012
        Address: 0xE0000
        Runtime Size: 128 kB
        ROM Size: 4096 kB
        Characteristics:
                PCI is supported
                PNP is supported
                BIOS is upgradeable
                BIOS shadowing is allowed
                Boot from CD is supported
                Selectable boot is supported
                EDD is supported
                3.5"/720 kB floppy services are supported (int 13h)
                Print screen service is supported (int 5h)
                8042 keyboard services are supported (int 9h)
                Serial services are supported (int 14h)
                Printer services are supported (int 17h)
                CGA/mono video services are supported (int 10h)
                ACPI is supported
                USB legacy is supported
                BIOS boot specification is supported
                Targeted content distribution is supported
                UEFI is supported
        BIOS Revision: 1.14
        Firmware Revision: 1.14
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    Some BIOSes have a debug mode (usually undocumented) where a serial or USB port is used to output the screen. Without knowing more about your laptop and BIOS version, nobody can really help you. – fpmurphy Aug 9 '15 at 8:44
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So using a combination of Lenovo's BIOS simulator (pretty neat: http://service.lenovo.partner-management.com/et.cfm?eid=1437) and Lenovo's manual for the machine, I was able to get the correct sequence of keystrokes to modify the "Boot Display Device" from LCD to analog VGA.

In the rare event anyone faces exactly this problem, here is how to solve it:

Boot as usual, and press Fn + F1 repeatedly to load BIOS. Once you are sure the OS is not loading (i.e. the BIOS setup as loaded), then: 1) Press Esc to clear any help menu that may have popped up 2) Press Right arrow key once 3) Press Down arrow key three times 4) Press Enter 5) Press Shift+"+" (i.e. type the "+" character) 6) Press Fn + F10 7) Press Enter

Now the system will reboot, and, if you have a VGA connection to a monitor established, you can test that it worked by Fn + F1 to ensure that the BIOS setup is visible this time

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