MIDDLEBURGH

Master Of The Bios

Life is a series of challenges to be overcome before moving on. Lessons are learned when we take a moment to reflect on how we addressed a challenge and the insights help us (or someone else) do better next time.(well that's the theory, grasshopper !!)

Ok you have a version of Linux which you wish to run on your PC and you have either

• - scared yourself shitless reading about the risks of dicking with your BIOS or
• - you have cojones, and have tried but failed to get it to boot

First hurdle (note the Olympic metaphor - I am after all in Hong Kong, home to the 2008 Equestrian Olympics): what bootable devices does your PC BIOS recognise?

Insert your "allegedly" bootable device into the appropriate orifice - eg a LiveCD in CD/DVD drive,USB flash or hard drive into USB socket etc, (re)boot and press the F button during the bootup sequence. On IBM Thinkpads this is F12 Go here for a clue about your PC's BIOS. This should get the BIOS to display the "Boot Menu" and hopefully your media/device will be on this list. If so select it and press enter. You should boot into linux and you haven't even changed your BIOS settings.

If your device/media is not listed select "Enter Setup". This should open a screen detailing the BIOS version etc. (see end of post if you get prompted for a password !!) DO NOT GET DISTRACTED !! You are now in "edit" mode with the potential to screw your system. Proceed directly to "startup" then "boot" to display the "Boot Order List". This list is build dynamically ie your BIOS recognises which bootable working devices are present and lists them in the order that they will be accessed (or not) during bootup. The system will boot from the first device it can. You can change the sequence and save the settings ie a device may be listed here even if no longer connected to the PC.(unlike the Boot Menu which only shows your connected devices.)

I have 4 IBM thinkpads of different vintages to play with, each showing similar but different boot options. The oldest refers to:

• Removable Devices (ie Legacy Floppy drives and the like )
• CD Rom-Drive (in more recent versions aka ATAPI and USB CD dives)
• HardDrive (in more recent versions aka IDE, ATA and USB hard drives)
• Network Boot (eg PCI LAN)
• IBA 4.0.22 (Intel Boot Agent 4.0.22 - haven't a clue !!!)

If,as on the oldest PC, there are items listed with a +indicator before them, you can select to open a submenu where you may find your device. If there are no USB devices listed anywhere (I am assuming you are trying to boot from a USB device) you may need to detour and enable USB support. Return to the BIOS Version screen, take the "configeration" then "USB" options and "enable" USB Bios support.

If your device is listed but doesn't boot it is either because there is a problem eg bad sectors etc (you may need to reformat it - see below) or more probably because you are booting from a device higher in the list (normally the fixed hard drive) Use an F button to resequence your device ahead (Instructions are on the right side of the boot sequence screen) Works for me!! Remember to unplug your device if you want to boot up normally and not from your device

If you have an error where the BIOS appears to recognise that the device is bootable, but there is an execution error when it tries to load. DON'T PANIC My experience (Been there-done that) is that BIOS is working fine but there is a problem with boot sector/loader on your media. Remove the media, press enter to trigger a reboot or enter the command "reboot". If you system has locked try control/alt/delete etc and as last resort switch off the PC. Actually the last resort when it won't switch off is to unplug the external power and take out main battery (notebooks).

The BIOS won't recognise a device if it is simply not bootable (there is an "flag" which can be toggled on/off in the boot sectors of your device which the bios recognises, ironically the easiest way to set it is using Linux.) or because the bios version simply doesn't support the device type.

In mega simple terms during boot up the bios identifies storage types which are bootable. If you have a device type that is not supported by your bios you may be able to reformat it such that the BOIS sees its it as a different type eg make a USB flash drive (FDD) appear to be a USB ZIP drive, USB floppy drive or Hard drive (HDD). The tool of choice for this recommended by everbody is the HP utility. (makes drive appear a HDD or floppy) The trick however is to be able to find a downloadable copy of the Utility and if you can't you should check all those minidisks you got with your USB devices - you may find an equivalent. I use it to reformat U3 enabled drives in particular

So you have a workable bios and bootable divice and LINUX still won't boot !!! You get somethink like "can't find kernel" The problem probably lies with the bootloader. During boot up the bios gets it's bootload instructions from the device boot member and if these are incorrect or damaged etc the system spits the dummy. There are three bootloading system typically in use with linux LILO, GrUB and Syslinux. To date I have only ever used the W32 version of syslinux to fix "Can't find kernel" problems (just make sure you fix the right disk ie the USB device and not your hard disk - otherwise you will stuff Windows!!)

Password Locked BIOS

Whilst most systems administrators implement OS level user passwords and lock down the administrator functions, many either overlook or deliberately do not lock down the BIOS. Where they have been diligent you may be promted for a password before you can edit BIOS settings. Personally I would go find another PC to play with. If you are brave You can however play PC mechanic and disconnect the CMOS battery and/or reset the mother board jump switches. This will have effect of resetting the BIOS to factory settings ie password gets wiped and clock reset. No one would Know if clock was reset until next PC audit when PC bios is discovered as open.

I had an animated discussion with our security team at work about this. It is trivial to boot an allegedly locked down Windows PC from Linux using a USB stick and copy files from the hard disk. This means that confidential information on a PC including emails can be can be stolen without leaving a trace.

Essentially it is the Edison Chen problem. Edison Chen is a HK actor with aspirations to be a director and win a Golden Horse Award. He video'd a number of local actresses giving him a blow job and these videos ended up the internet causing public outcry. (based on the evidence he has a long way to go to get an award as either a director or a horse although he is up for nomination as an ASS!!) They were stolen from his hard disk which wasn't encrypted when his PC went in for repair. The bottom line is encrypt your hard disk. We know it works - we've tested it !!

Wow - where did that come from !! Boy am I glad I got it out of my system !!!!

Posted at 8/06/2008 01:44:00 pm by David Middleburgh   Permalink

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