Hands-on Guide for Linux /boot file and folders

by Content Team

9 January 2024

File System, Linux

Linux /boot and its architecture!

Guide outline

1.1. Overview
1.2. The Root Directory
1.3. /bin
1.4. /boot
1.5. /dev
1.6. /etc
1.7. /home
1.8. /initrd
1.9. /lib
1.10. /lost+found
1.11. /media
1.12. /mnt
1.13. /opt
1.14. /proc
1.15. /root
1.16. /sbin
1.17. /usr
1.18. /var
1.19. /srv
1.20. /tm

2. Glossary

Additional Linux Resources

Here is a list of resources for learning Linux:

Resources for System Administrators

Linux System Admin Guide- What is Linux Operating System and how it works
Linux System Admin Guide- What are Directory Tree and Filesystem Hierarchy in Linux
Linux System Admin Guide- Introduction to Linux File Systems for System Admins
Linux System Admin Guide- Overview of Linux Virtual Memory and Disk Buffer Cache
Linux System Admin Guide- Best Practices for Monitoring Linux Systems
Linux System Admin Guide- Best Practices for Performing Linux Boots and Shutdowns
Linux System Admin Guide- Best Practices for Making and Managing Backup Operations

Resources for Linux Kernel Programmers

How Linux Operating System Memory Management works
Comprehensive Review of Linux Kernel Operating System Processes
Comprehensive Review of Linux File System Architecture and Management
What are mechanisms behind Linux Kernel task management
How Linux Kernel Sources and Functions work
Comprehensive look at how Linux Data Structures work

Hands-on Linux classes

Linux Operating System Distributions

Comprehensive list of all Linux OS distributions
Comprehensive list of all special purpose Linux distributions
Comprehensive list of all secure Linux distributions for cybersecurity professionals

1.4. /boot

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).

/boot/boot.0300

Backup master boot record.

/boot/boot.b

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.

/boot/chain.b

Used to boot non-Linux operating systems.

/boot/config-kernel-version

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.

/boot/os2_d.b

Used to boot to the 0S/2 operating system.

/boot/map

Contains the location of the kernel.

/boot/vmlinuz, /boot/vmlinuz-kernel-version

Normally the kernel or symbolic link to the kernel.

/boot/grub

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.

/boot/grub/device.map