Linux Format - UK (2019-12)

72 LXF257 December 2019 http://www.linuxformat.com

TUTORIALS Customising GRUB

compiling. If you do need to compile, the tools are the

common ones: GCC, make and binutils. For ordinary

tweaking, you have plenty of tools available together

with GRUB itself. Please remember that you are playing

with the boot system: do something wrong and you may

need to do a recovery (why not see our recovery feature

on page 44) action. This can take time and you may lose

all your data.

Wise readers always have important data backed up

using the cloud, Clonezilla or the backup application

delivered with your distribution. If you want to boot

without GRUB, you may need to compile your kernel.

32-bit vs 64-bit

GRUB comes as both 32-bit and 64-bit, though in

today’s world, the former is seldom useful. However,

you may have an old system lying around that you want

to boot from a memory stick, so consider getting GRUB

32-bit for this edge case. While you can start a 32-bit

OS with GRUB 64-bit, you may need 32-bit GRUB only

for the case of an old 32-bit computer. This is common

for old (2006) iMac computers. The limitation is in the

UEFI being 32-bit, making GRUB unbootable.

The package that handles this is grub-efi-ia32; you

will ordinarily have to do a bit of work to make it work.

sudo apt install grub-efi-ia32 grub-efi-ia32-bin

You should be aware that when you install this you

change the GRUB version on the machine you’re

working on. This could be a disaster if you do it on your

ordinary machine. The safe alternative is to create one

ooting your PC is something that just happens

and most people don’t even give it a second

thought, unless it’s brain-numbingly slow or

something goes about as wrong as Brexit has. This is

largely as most distributions, when you install them,

automatically create the partitions and sets up any

dual-boot required. Beyond that, most users leave it be

and get on with their lives.

This makes the thing we call GRUB and generally the

entire boot process a mystery to most people. In this

article, you can start clearing the fog a little bit and see

what you can do to improve things. If dual-booting isn’t

on your agenda, you still have other interesting options

to explore along expanding your knowledge.

If you’re wondering what it stands for, GNU GRUB

is the GRand Unified Bootloader. The bootloader is

the software glue that sits between the BIOS/UEFI

firmware that kickstarts your PC hardware into life and

the Linux (or Windows) kernel being run – started by

the bootloader – and then the Process ID One (PiD1)

‘init’, very often Systemd.

Depending on what you are after, you may need to

compile (don’t panic!) GRUB or even the kernel. One

interesting feature to consider is EFI_STUB, which

makes the kernel a boot loader that you can set to be

the first to load. That will be faster, but you will be

unable to dual-boot your machine, which can make life

complicated. Single-booting is not necessarily bad

though – have you decided to stick with Linux or do you

need other operating systems? If you only have one or

two applications that need Windows, you can run that

in a virtual machine.

In most cases, your GRUB binary is good to go, as

you can make many tweaks to your system without

Plop Linux comes

with rEFInd as its

default bootloader.

Create a virtual

machine with it

and you can start

the rEFInd shell to

configure the boot.

Most standard boot menus on Linux machines are blue like this, but

you have the power to change all of this.

Get more from your

grubby boot menu

Mats Tage Axelsson takes you through the intricacies of GRUB

that you never thought you would wonder about...

Mats Tage

Axelsson

keeps fighting the

tide, showing you

what even he can

do using Linux to

make the world

a better place.

B

GRUB

OUR

EXPERT

Practice in

a virtual

machine, as any

experiments

with GRUB

can make

your system

unbootable.

Most features

will behave the

same in a VM

as on your

real machine.

72 LXF257 December 2019 http://www.linuxformat.com

TUTORIALS Customising GRUB

compiling.If youdoneedtocompile,thetoolsarethe

commonones:GCC,makeandbinutils. Forordinary

tweaking,youhaveplentyoftoolsavailabletogether

withGRUBitself.Pleaserememberthatyouareplaying

withthebootsystem:dosomethingwrongandyoumay

needtodoa recovery(whynotseeourrecoveryfeature

onpage44)action.Thiscantaketimeandyoumaylose

allyourdata.

Wisereadersalwayshaveimportantdatabackedup

usingthecloud,Clonezillaorthebackupapplication

deliveredwithyourdistribution.If youwanttoboot

withoutGRUB, youmayneedtocompileyourkernel.

32-bitvs64-bit

GRUBcomesasboth32-bitand64-bit,thoughin

today’sworld,theformerisseldomuseful.However,

youmayhaveanoldsystemlyingaroundthatyouwant

tobootfroma memorystick,soconsidergettingGRUB

32-bitforthisedgecase.Whileyoucanstarta 32-bit

OSwithGRUB64-bit,youmayneed32-bitGRUBonly

forthecaseofanold32-bitcomputer.Thisiscommon

forold(2006)iMaccomputers.Thelimitationisinthe

UEFIbeing32-bit,makingGRUBunbootable.

Thepackagethathandlesthisisgrub-efi-ia32;you

willordinarilyhavetodoa bitofworktomakeit work.

sudoaptinstallgrub-efi-ia32grub-efi-ia32-bin

Youshouldbeawarethatwhenyouinstallthisyou

changetheGRUBversiononthemachineyou’re

workingon.Thiscouldbea disasterif youdoit onyour

ordinarymachine.Thesafealternativeistocreateone

ootingyourPCissomethingthatjusthappens

andmostpeopledon’tevengiveit a second

thought,unlessit’sbrain-numbinglyslowor

somethinggoesaboutaswrongasBrexithas.Thisis

largelyasmostdistributions,whenyouinstallthem,

automaticallycreatethepartitionsandsetsupany

dual-bootrequired.Beyondthat,mostusersleaveit be

andgetonwiththeirlives.

ThismakesthethingwecallGRUBandgenerallythe

entirebootprocessa mysterytomostpeople.Inthis

article,youcanstartclearingthefoga littlebitandsee

whatyoucandotoimprovethings.If dual-bootingisn’t

onyouragenda,youstillhaveotherinterestingoptions

toexplorealongexpandingyourknowledge.

If you’rewonderingwhatit standsfor,GNUGRUB

istheGRandUnifiedBootloader.Thebootloaderis

thesoftwaregluethatsitsbetweentheBIOS/UEFI

firmwarethatkickstartsyourPChardwareintolifeand

theLinux(orWindows)kernelbeingrun– startedby

thebootloader– andthentheProcessIDOne(PiD1)

‘init’,veryoftenSystemd.

Dependingonwhatyouareafter,youmayneedto

compile(don’tpanic!)GRUBoreventhekernel.One

interestingfeaturetoconsiderisEFI_STUB,which

makesthekernela bootloaderthatyoucansettobe

thefirsttoload.Thatwillbefaster,butyouwillbe

unabletodual-bootyourmachine,whichcanmakelife

complicated.Single-bootingisnotnecessarilybad

though– haveyoudecidedtostickwithLinuxordoyou

needotheroperatingsystems?If youonlyhaveoneor

twoapplicationsthatneedWindows,youcanrunthat

ina virtualmachine.

Inmostcases,yourGRUBbinaryisgoodtogo,as

youcanmakemanytweakstoyoursystemwithout

Plop Linux comes

with rEFInd as its

default bootloader.

Create a virtual

machine with it

and you can start

the rEFInd shell to

configure the boot.

MoststandardbootmenusonLinuxmachinesarebluelike this, but

youhavethepowertochangeallofthis.

Get more from your

grubby boot menu

Mats TageAxelsson takes you through the intricacies of GRUB

thatyouneverthought you would wonder about...

MatsTage
Axelsson
keeps fighting the
tide, showing you
what even he can
do using Linux to
make the world
a better place.

B

GRUB

OUR

EXPERT

Practicein

a virtual

machine,asany

experiments

withGRUB

canmake

yoursystem

unbootable.

Mostfeatures

willbehavethe

sameina VM

asonyour

realmachine.