TABLEOFCONTENTS:
1.HowComputerBootsUp?
2.BootSectors
3.BootinginWindows
4.BootinginLinux
HowComputerBootsUp?
Linux
Thebootloaderloadskernelaswellasthetemporary
filesystembeforetheactualfilesystemisloaded.In
earlierversionsofkernelinitrd(ramdisk)wasused
butsince2.6kernelinitramfs(ramfilesystem)isin
use.Thisisjusttemporary,incaseofembedded
systemitissometimesthefinalfilesystem.
IncaseofLinuxtheimageofthekernelisdividedintotwopartsonthebasisofitsloadingthatisrealmodeand
protectedmode.Theprocessalwaysoccursintherealmode.Thefirstentrypointintheinitializationofkernelis
head.S(arch/i386/boot/head.S),whichisassemblylanguagewrittenfilewhosetaskisbasichardwaresetup.
Fromherethereisjumptohead.S(thisispresentinboot/compresseddirectory)whosetaskissetthebasic
environmentandcallsdecompress_kernel(presentinboot/compresses/misc.c)andthentostartup_32(presentin
kernel/head.S).Thenitmovestomain.cpresentinarch/x86/bootdirectory.
Afterallthese/sbin/init,/etc/init,/bin/init,and/bin/sharecalledintheorder;thefirstuserprocessisinitandthey
readetc/events.doretc/inittab.Hencethesystemstarts.
Incaseoflinuxmachinesthebootingprocedurehashardlychangedwithtime;exceptforinitrdtoinitramfs.
Thisishowcomputerbootsupandweseeourloginscreen.
TUT021
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