This directory contains everything required for the boot process except for configuration files not needed at boot time (the most notable of those being those that belong to the GRUB boot-loader) and the map installer. Thus, the /boot directory stores data that is used before the kernel begins executing user-mode programs. This may include redundant (back-up) master boot records, sector/system map files, the kernel and other important boot files and data that is not directly edited by hand. Programs necessary to arrange for the boot loader to be able to boot a file are placed in /sbin. Configuration files for boot loaders are placed in /etc. The system kernel is located in either / or /boot (or as under Debian in /boot but is actually a symbolically linked at / in accordance with the FSSTND).
Backup master boot record.
This is installed as the basic boot sector. In the case of most modern distributions it is actually a symbolic link to one of four files /boot/boot-bmp.b, /boot/boot-menu.b, /boot/boot-text.b, /boot/boot-compat.b which allow a user to change the boot-up schema so that it utilises a splash screen, a simple menu, a text based interface or a minimal boot loader to ensure compatibility respectively. In each case re-installation of lilo is necessary in order to complete the changes. To change the actual 'boot-logo' you can either use utilities such as fblogo or the more refined bootsplash.
Used to boot non-Linux operating systems.
Installed kernel configuration. This file is most useful when compiling kernels on other systems or device modules. Below is a small sample of what the contents of the file looks like.
CONFIG_X86=y
CONFIG_MICROCODE=m
CONFIG_X86_MSR=m
CONFIG_MATH_EMULATION=y
CONFIG_MTRR=y
CONFIG_MODULES=y
CONFIG_MODVERSIONS=y
CONFIG_SCSI_DEBUG=m
CONFIG_I2O=m
CONFIG_ARCNET_ETH=y
CONFIG_FMV18X=m
CONFIG_HPLAN_PLUS=m
CONFIG_ETH16I=m
CONFIG_NE2000=m
CONFIG_HISAX_HFC_PCI=y
CONFIG_ISDN_DRV_AVMB1_C4=m
CONFIG_USB_RIO500=m
CONFIG_QUOTA=y
CONFIG_AUTOFS_FS=m
CONFIG_ADFS_FS=m
CONFIG_AFFS_FS=m
CONFIG_HFS_FS=m
CONFIG_FAT_FS=y
CONFIG_MSDOS_FS=y
CONFIG_UMSDOS_FS=m
CONFIG_FBCON_VGA=m
CONFIG_FONT_8x8=y
CONFIG_FONT_8x16=y
CONFIG_SOUND=m
CONFIG_SOUND_CMPCI=m
CONFIG_AEDSP16=m
As you can see, it's rather simplistic. The line begins with the configuration option and whether it's configured as part of the kernel, as a module or not at all. Lines beginning with a # symbol are comments and are not interpreted during processing.
Used to boot to the 0S/2 operating system.
Contains the location of the kernel.
Normally the kernel or symbolic link to the kernel.
This subdirectory contains the GRUB configuration files including boot-up images and sounds. GRUB is the GNU GRand Unified Bootloader, a project which intends to solve all bootup problems once and for all. One of the most interesting features, is that you don't have to install a new partition or kernel, you can change all parameters at boot time via the GRUB Console, since it knows about the filesystems.
Maps devices in /dev to those used by grub. For example, (/dev/fd0) is represented by /dev/fd0 and (hd0, 4) is referenced by /dev/hda5.
Grub configuration file.
Grub boot-up welcome message.
Grub boot-up background image.