Linux filesystem hierarchy

4.3 Where Data is Stored (Weight: 3)

📘Linux Essentials (LPI 010-160)

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1. Root Directory (/)

• The top-level directory in Linux.
• All other directories and files are under /.
• Examples of important directories under / will be discussed below.

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2. /bin – Essential User Binaries

• Contains essential command-line programs needed for basic tasks.
• Programs in /bin can be used even in single-user mode (recovery mode).
• Examples:
  • ls – list files
  • cp – copy files
  • mv – move files
  • cat – view file content

Exam Tip: Remember /bin contains essential commands for all users.

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3. /sbin – System Binaries

• Contains system programs used mainly by the system administrator (root).
• Used for system maintenance and administration.
• Examples:
  • ifconfig – manage network interfaces
  • reboot – reboot the system
  • fdisk – manage disk partitions

Exam Tip: /sbin = admin commands.

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4. /etc – Configuration Files

• Contains system-wide configuration files.
• Almost all programs store their configurations here.
• Examples:
  • /etc/passwd – stores user account information
  • /etc/fstab – filesystems to mount at boot
  • /etc/ssh/sshd_config – SSH server settings

IT Example: If an IT admin wants to change network settings, they might edit /etc/network/interfaces.

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5. /home – User Home Directories

• Each user has a personal directory under /home.
• Stores user files and personal settings.
• Example:
  • /home/pooja/ – files for the user pooja

IT Example: Developers store their project files under their /home directories.

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6. /root – Root User Home

• This is the home directory for the root user (the superuser).
• Different from /home.
• Example: /root/.bashrc stores root’s shell settings.

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7. /lib – Essential Libraries

• Stores shared libraries needed by programs in /bin and /sbin.
• Libraries are like “helper files” for programs to run.
• Examples:
  • libc.so.6 – core system library
  • libm.so – math functions

Exam Tip: /lib is for essential libraries for basic system operation.

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8. /usr – User Programs and Data

• Contains user applications and utilities that are not essential for booting.
• Subdirectories:
  • /usr/bin – non-essential user programs (e.g., vim, firefox)
  • /usr/sbin – admin programs for non-critical system tasks
  • /usr/lib – libraries for /usr/bin and /usr/sbin
  • /usr/share – shared data like icons, documentation, fonts

IT Example: Software installed from the package manager usually goes here.

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9. /var – Variable Data

• Contains files that change frequently.
• Examples:
  • /var/log – system logs
  • /var/mail – user emails
  • /var/spool – print jobs or scheduled tasks

IT Example: Checking /var/log/syslog helps troubleshoot system errors.

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10. /tmp – Temporary Files

• Used for temporary files created by users or programs.
• Files in /tmp are deleted on reboot on many systems.

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11. /dev – Device Files

• Represents hardware devices like disks, USB drives, printers.
• Files in /dev are special interfaces to devices.
• Examples:
  • /dev/sda – first hard drive
  • /dev/tty – terminal devices

IT Example: Mounting a USB drive uses /dev/sdb1 as the device file.

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12. /mnt and /media – Mount Points

• /mnt – temporary mount points for manual mounting.
• /media – used for removable media like USB drives or CDs.
• Example: /media/usbdrive/ for a USB stick.

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13. /boot – Boot Loader Files

• Contains files required to boot Linux.
• Examples:
  • Kernel files: vmlinuz
  • Bootloader configs: grub/

Exam Tip: /boot is critical for booting; don’t delete files here.

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14. /opt – Optional Software

• Used for third-party or optional software.
• Often used by commercial software.
• Example: /opt/google/chrome/

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15. /proc – Process and Kernel Information

• A virtual filesystem that provides info about running processes and kernel.
• Example:
  • /proc/cpuinfo – CPU details
  • /proc/meminfo – memory details

IT Example: Admins check /proc to monitor system hardware and performance.

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16. /sys – System Files

• Another virtual filesystem for kernel and hardware information.
• Mostly used by the system, scripts, and administrators.

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Quick Reference Table for Exams

Directory	Purpose	Example Use
/	Root directory	Top of filesystem
/bin	Essential commands	ls, cp
/sbin	Admin commands	fdisk, reboot
/etc	Configuration files	passwd, ssh/sshd_config
/home	User directories	/home/pooja/
/root	Root user home	/root/.bashrc
/lib	Essential libraries	libc.so.6
/usr	User programs	/usr/bin/vim
/var	Variable data	Logs, mail
/tmp	Temporary files	Temp files by programs
/dev	Device files	/dev/sda, /dev/tty
/mnt	Mount points	Manual mounts
/media	Removable media	USB drives
/boot	Boot files	Kernel, GRUB
/opt	Optional software	Third-party apps
/proc	Process info	/proc/cpuinfo
/sys	System info	Kernel data

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Key Points for the Exam

1. All Linux files and directories start at /.
2. /bin and /sbin are for essential commands; /usr is for additional programs.
3. Configuration files are mostly in /etc.
4. User data is in /home.
5. Logs and dynamic data are in /var.
6. Device files live in /dev.
7. Temporary files in /tmp.
8. Virtual filesystems /proc and /sys provide system info without using real disk space.
9. /opt is optional, /boot is critical for booting.

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This content covers everything you need for the Linux filesystem hierarchy section of LPI 010-160.