One of the most important aspects of any operating system is how it organizes and manages the files and directories on the disk. Linux, being a Unix-like system, follows a hierarchical structure that is both logical and consistent. In this blog post, we will explore the Linux file hierarchy system and learn some of the key features and functions of its main components.
The Root Directory
- The root directory, denoted by a single slash (/), is the topmost level of the file system. It contains all other files and directories as its subdirectories. The root directory is not to be confused with the root user, who is the superuser or administrator of the system. The root user can access and modify any file or directory on the system, while other users may have limited permissions depending on their group membership and ownership.
The root directory contains several important subdirectories, such as:
- /bin: This directory contains essential binary executables that are needed for basic system operations, such as ls, cp, mv, rm, etc. These binaries are usually available to all users.
- /boot: This directory contains the files and configurations needed for booting the system, such as the kernel image, the initramfs image, and the bootloader (e.g., GRUB).
- /dev: This directory contains device files that represent hardware devices attached to the system, such as disks, terminals, printers, etc. These files are used to communicate with the devices using special system calls.
- /etc: This directory contains configuration files for various system services and applications, such as network settings, user accounts, cron jobs, etc. These files are usually editable only by the root user or a sudoer.
- /home: This directory contains the home directories of regular users, where they can store their personal files and settings. Each user has a subdirectory under /home with their username (e.g., /home/alice).
- /lib: This directory contains shared libraries that are needed by the binaries in /bin and /sbin. These libraries provide common functionality and reduce code duplication.
- /media: This directory contains mount points for removable media devices, such as USB drives, CDs, DVDs, etc. These devices are usually mounted automatically when inserted or plugged in.
- /mnt: This directory contains mount points for temporary or external file systems, such as network shares, partitions, etc. These file systems are usually mounted manually by the user or a script.
- /opt: This directory contains optional or third-party software that is not part of the standard Linux distribution. These software may have their own subdirectories under /opt with their name or vendor (e.g., /opt/google).
- /proc: This directory contains virtual files that provide information about the system processes and kernel parameters. These files are not stored on the disk but are generated dynamically by the kernel. For example, /proc/cpuinfo shows information about the CPU(s) on the system.
- /root: This directory is the home directory of the root user. It is not recommended to use this directory for storing personal files, as it may pose a security risk.
- /run: This directory contains runtime data for various system services and applications, such as process IDs, sockets, locks, etc. These data are stored in memory and are cleared at every boot.
- /sbin: This directory contains binary executables that are used for system administration and maintenance, such as fdisk, ifconfig, mount, etc. These binaries are usually accessible only by the root user or a sudoer.
- /srv: This directory contains data for server-related services, such as web servers, FTP servers, database servers, etc. These data may vary depending on the service configuration and usage.
- /sys: This directory contains virtual files that provide information about the system hardware and devices. These files are not stored on the disk but are generated dynamically by the kernel. For example, /sys/class/net shows information about the network interfaces on the system.
- /tmp: This directory contains temporary files that are created by various system services and applications. These files are usually deleted automatically after a certain period of time or at every boot.
- /usr: This directory contains user-related files that are not essential for booting the system but are needed for normal operation, such as binaries, libraries, documentation, etc. These files are usually shared among all users.
- /var: This directory contains variable data that change frequently over time, such as logs, caches, spools, etc. These data may grow in size depending on the system activity and usage.
Conclusion
The Linux file hierarchy system is designed to provide a clear and consistent way of organizing and accessing files and directories on the disk. By following this structure, users can easily locate and manage their files and directories without confusion or conflict. Moreover, this structure allows for flexibility and customization according to different needs and preferences.
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