Linux (General)

• Basic Commands Overview
• Filesystem Hierarchy
• Linux File Systems
• Ext4: the reliable all-rounder
• Btrfs: modern and feature-packed
• XFS: the workhorse
• ZFS: the file system to end all file systems

Basic Commands Overview

Command	Description	Package
base64	base64 encode/decode data and print to standard output	coreutils
basename	strip directory and suffix from filenames	coreutils
cat	concatenate — combine the output of files and print to standard output	coreutils
cd	Change Directory — navigate directories on the filesystem	built-in
chmod	change file mode bits (permissions) for files and directories	coreutils
chown	change file owner and group	coreutils
clear	clear the terminal content	clear
cp	copy files	coreutils
csplit	split a file into sections determined by context lines	coreutils
dd	convert and copy a file	coreutils
df	Disk Free — report overall file system space usage	coreutils
diff	show differences between two files line by line	diffutils
dirname	print the directory path if the passed file	coreutils
du	Disk Usage — show file system usage for a given directory	coreutils
echo	display a line of text	built-in
find	search for files in a given directory	findutils
grep	search for text	grep
head	display the first X lines of a file (default 10)	coreutils
history	print the history of issued commands	built-in
jobs	display currently running jobs	built-in
kill	terminate a process	util-linux
ls	list directory contents	coreutils
man	Manual — display the documentation of a given command	man
mkdir	create a directory	coreutils
mv	move (and rename) files	coreutils
ping	check if a server is reachable	iputils
printenv	print information about currently set environment variables	coreutils
printf	format and print data	coreutils
pwd	Print Working Directory — returns the current working directory	built-in
rm	remove files and directories (caution: no undo!)	coreutils
scp	OpenSSH secure file copy	openssh
sha256sum	compute and check SHA256 message digest (variants for SHA1, SHA224, SHA384 and SHA512 exist)	coreutils
sort	sort lines of text files	coreutils
sudo	Super User Do — execute commands as root	sudo
tail	display the last X lines of a file (default 10)	coreutils
tar	archiving utility, compression optional	tar
top	display Linux processes	procps-ng
touch	create an empty file	coreutils
uname	Unix Name — print system information	coreutils
unzip	list, test and extract compressed files in a ZIP archive	unzip
useradd	create a new user or update default new user information	shadow
userdel	delete a user account and related files	shadow
wget	download files from the internet	wget
zip	package and compress (archive) files	zip

Filesystem Hierarchy

The Filesystem Hierarchy Standard (FHS) is a set of guidelines that define the directory structure of a Linux operating system. This standard specifies the names and locations of directories, files, and other file system objects that are essential for the proper functioning of the Linux operating system.

Directory	Description
/bin	binary files of basic commands
/boot	static files of the bootloader
/dev	device files
/etc	host-specific system configuration
/lib	basic dynamic libraries and kernel modules
/media	mount point for removable media
/mnt	for temporarily mounted file system
/opt	additional application programs
/run	relevant data for running processes
/sbin	essential binary files of the system
/srv	data for services
/tmp	temporary files
/usr	secondary hierarchy
/var	variable data

Root Directory (/)

The root directory is the highest level of the file system hierarchy. It contains all other directories and files in the system. All directories and files in the system are located either directly or indirectly under the root directory.

/bin Directory

NOTE: On most modern Linux distributions, /bin is actually a symbolic link pointing to /usr/bin.

The /bin directory contains essential binary files that are required for the system to function properly. These files are used by all users of the system, and they include basic system commands such as ls, cp, and mv. The /bin directory must not contain any subdirectories. Each installed package places its main executables here.

/boot Directory

The /boot directory contains the files needed by the bootloader for the Linux kernel, including the kernel itself, initrd (initial RAM disk), and boot loader configuration files. The bootloader is the program that loads the operating system when the computer starts up. The files in /boot are essential for the bootloader to function properly.

/dev Directory

The /dev directory contains device files that represent hardware devices connected to the system. These files allow applications and users to interact with the hardware devices such as keyboards, mice, and disk drives using standard input/output operations.

There's different types of device files:

Type	Description
Character device	Communication with a character device is based on the exchange of characters, such as individual bytes
Block device	Communication with a block device is based on the exchange of entire blocks of data
Pseudo device	Devices that are not corresponding to any real hardware actually present on the system

Each device file in the /dev directory represents a specific hardware device. These files are created dynamically and disappear when the device is disconnected.

Some examples of device files:

File	Description
/dev/dm-X	Logical volumes created using LVM (device manager). X = index of device manager volume
/dev/hdX	IDE hard drives or other storage devices. Common in older systems. X = lower-case letter indicating order of discovery
/dev/hdXY	Partitions on IDE storage device. X = disk Y = partition on that disk
/dev/jsX	Device file for a joystick/gamepad. X = index of a joystick connected to the system
/dev/mdX	Software RAID devices (meta disk). X = meta disk group index
/dev/mmcblkX	MMC/SD cards and eMMC storage devices. X = index of an MMC storage device
/dev/nvmeXnY	NVMe solid-state drives. X = controller index Y = device index on that controller
/dev/nvmeXnYpZ	Partitions on NVMe storage device. X = controller index Y = device index on that controller Z = partition on that device
/dev/null	Pseudo-device that always outputs EOF (end of file). Output redirected to it is immediately discarded.
/dev/random	Pseudo-device that generates random data (blocking).
/dev/sdX	SCSI or SATA hard drives and other storage devices. Common in modern systems. X = lower-case letter indicating order of discovery.
/dev/sdXY	Partitions on SCSI or SATA storage device. X = disk Y = partition on that disk
/dev/srX	CD-ROM or DVD-ROM drives. X = index of an optical drive connected to the system
/dev/ttyX	Device file for the terminal. X = index of a terminal
/dev/urandom	Pseudo-device that generates random data (non-blocking)
/dev/vdX	Virtual storage device. X = lower-case letter indicating order of discovery
/dev/vdXY	Partitions on a virtual storage device. X = disk Y = partition on that disk
/dev/videoX	Device file for a webcam. X = index of a webcam connected to the system

/etc Directory

The /etc (editable text configuration) directory contains system configuration files. These files are used to configure the system and its applications. Examples of files in this directory include passwd and group files, which contain user and group information, and fstab file, which contains information about file systems that are mounted at boot time. The /etc directory is one of the most important directories in the system, as it contains configuration files that enable system administrators to customize the system to their needs.

Some examples of what might be of particular interest:

Directory/File	Description
/etc/opt/	Configuration files for software installed to /opt.
/etc/security/	Configuration files for PAM (Pluggable Authentication Modules).
/etc/skel/	Configuration files that are copied to a newly created user's /home directory.
/etc/X11/	Configuration files for the X Window System which provides a graphical user interface for Linux.
/etc/crontab	Configuration file uniquely formatted to automate system tasks on a set schedule.
/etc/fstab	Contains information about file systems and partitions automatically mounted at system startup.
/etc/group	Contains information about user groups, including group names and group IDs.
/etc/hosts	Configuration file that maps hostnames to IP addresses.
/etc/logrotate.conf	Configuration file for the logrotate utility, managing system log files.
/etc/passwd	Stores user account information such as usernames, user IDs, home directories, and login shells.
/etc/profile	Contains system-wide environment variables and other startup scripts.
/etc/resolv.conf	DNS resolver file which specifies how the system leverages DNS to resolve hostnames.
/etc/shadow	Contains encrypted user passwords and other password-related information.
/etc/ssh/sshd_config	Configuration file for the SSH server, which allows secure remote access to the system.
/etc/sudoers	Contains rules for allowing or denying sudo privileges to users and groups.

/home Directory

The /home directory contains the personal files for all users in the system. Each user has a subdirectory of their name in the /home directory that contains their documents, pictures, music, and individual application settings. Each user's home directory is private, and other users cannot access the files in that directory without the user's permission.

NOTE: A user's personal home directory can be shortened to ~.

NOTE: Directories and files starting with a period . are considered hidden.

Some examples for directories/files in a user's home directory could include:

Directory/File	Description
~/.config/	Contains configuration files for applications that are specific to a user.
~/.gnupg/	Contains user-specific configuration files for GnuPG (GNU Privacy Guard).
~/.local/	Contains user-specific data files for applications that are installed system-wide.
~/.mozilla/	Contains user-specific configurations and settings for Firefox.
~/.ssh/	Contains user-specific configuration files and private/public keys for SSH (Secure Shell) connections.
~/.bashrc, ~/.zshrc	Contains user-specific configurations for the user's terminal emulator.

These hidden directories in a user's home directory are important for ensuring that user-specific data and configuration files are stored in a separate location from system-wide files. This separation enables users to customize their system to their needs without affecting other users or the core system.

/lib Directory

NOTE: On most modern Linux distributions, /lib is actually a symbolic link pointing to /usr/lib.

The /lib directory (or /lib64 for 64-bit systems) is a crucial component of the operating system. It contains shared libraries that are required by programs in /bin and /sbin directories, as well as other applications. These libraries provide functionality for many basic system operations, such as networking, file handling, and encryption. Without these libraries, the system would not be able to perform many of its fundamental functions. It is important to ensure that the files in /lib are always up-to-date and compatible with the system's other components to guarantee smooth operation.

In addition to the shared libraries, the /lib directory contains other important files, such as kernel modules (/lib/modules/) and firmware files (/lib/firmware/). Kernel modules are small programs that can be loaded and unloaded dynamically into the kernel without having to reboot the system. These modules provide additional functionality to the system, such as support for new hardware or file systems. Firmware files, on the other hand, contain low-level software that is used to control hardware devices, such as network adapters (especially WiFi) or graphics cards.

Directories/Files	Description
/lib/firmware/	Contains firmware files needed by devices to function properly, e.g. WiFi adapters and graphics cards.
/lib/security/	Contains authentication modules for PAM (Pluggable Authentication Modules).
/lib/systemd/	Contains files for the systemd system and service manager. Also contains systemd unit files.

/media Directory

The /media directory contains mount points for removable media devices such as USB drives and CD/DVDs. When a removable device is mounted, its contents appear in a subdirectory under the /media directory. The /media directory is used to manage removable media devices, and it allows users to access the files on those devices as if they were part of the file system.

/mnt Directory

The /mnt directory is used to temporarily mount file systems. This directory is typically used by system administrators when they need to mount a file system for a short period of time. The /mnt directory is used to access file systems that are not part of the main file system, such as network file systems or file systems on removable media devices.

/opt Directory

The /opt directory is used for optional software packages that are not part of the main operating system. Examples of software that might be installed in the /opt directory include proprietary software packages or third-party software that is not included with the distribution's main software repositories.

Examples of software you might see in this directory:

Directory/File	Description
/opt/1Password/	Password manager from Agile Bits
/opt/discord/	Discord VoiP client
/opt/google/	Google Chrome web browser
/opt/quake3/	Quare 3 Arena from id Software
/opt/spotify/	Spotify music streaming client
/opt/visual-studio-code/	Visual Studio Code editor from Microsoft

/proc Directory

The /proc directory is a virtual directory that contains information about running processes and system resources. This directory provides a way for processes to communicate with the kernel and allows system administrators to monitor system performance. The files in the /proc directory are not actual files, but rather a virtual representation of system resources. The /proc directory is used by system administrators to monitor system performance and diagnose system problems.

Directory/File	Description
/proc/cpuinfo	Contains information about the CPU, e.g. model name, number of cores, and clock speed.
/proc/meminfo	Contains memory usage information including swap storage use.
/proc/modules	Contains a list of all the modules being used by the kernel.
/proc/swaps	Contains information only about swap storage.
/proc/sys	Contains files that are used to manage kernel parameters.
/proc/version	Contains Linux version information.

/root Directory

The /root directory is the home directory for the root user. This directory contains the root user's personal files and settings. The root user is the most powerful user on the system, and has access to all files and directories on the system.

/run Directory

The /run directory is a unique and important directory in the Linux operating system that contains runtime data that is used by the system and applications. This data is volatile as it is mounted as a tmpfs filesystem that is only stored in system memory and its contents are lost when the system is rebooted.

The data stored in the /run directory is updated frequently and automatically by the system and applications. The directory is also used as a mount point for systemd, a system and service manager that is used in most modern Linux distributions. Systemd is responsible for managing system services, and it also uses the /run directory to store runtime data for these services.

The /run directory is also used for user mounted storage mediums like CDs, DVDs, USB drives and network shares.

/sbin Directory

NOTE: On most modern Linux distributions, /sbin is actually a symbolic link pointing to /usr/bin.

The /sbin directory contains essential system binaries that are used for system administration tasks, such as configuring the network or managing user accounts. These files are typically used by system administrators and are not intended for everyday use.

/srv Directory

The /srv directory is used to store data that is served by the system, and it is typically used by web servers, FTP servers, and other server applications.

Other directories that are used for different purposes include:

Directory/File	Description
/srv/ftp/	Contains files that an FTP server uses to store all of the files that can be accessed by the FTP server.
/srv/www/, /srv/http/	Contains files that are served by a web server (sub-directory is distribution specific).

/sys Directory

The /sys directory is a fundamental component of the Linux filesystem hierarchy and an essential tool for hardware management and configuration. This directory is structured in such a way that each hardware device is represented by a directory tree and a set of files, providing users with detailed information about the device's properties and allowing them to adjust, among other things, power management settings, device parameters, and monitor the device's status. The files in the /sys directory are not actual files, but rather a virtual representation of hardware devices. They are re-created upon every boot of the system and mounted as a virtual sysfs filesystem.

/tmp Directory

The /tmp directory is used for temporary files. This directory is typically used by applications to store non-critical files and it is typically cleaned out on a regular basis to prevent the accumulation of unnecessary files. It is writable to any user and is ideal for using it as a scratchpad type of directory. The /tmp directory is mounted as a tmpfs type of filesystem, which means its contents are stored in the system's memory for fast access. However, this also means that it is generally not recommended putting large files there as to not exhaust the system's memory with large amoounts of data.

/usr Directory

The /usr (Unix System Resources) directory is used to store programs, libraries, documentation and data that are not part of the core operating system, but that are still important for the system to function. Examples of programs that might be installed in the /usr directory include text editors, email clients, and games.

Some other examples of contents of the /usr directory:

Directory/File	Description
/usr/bin/	Contains executable binaries of applications
/usr/bin/gcc/	Binaries for compiling all sorts of source code of different programming languages
/usr/include/	Source code header files for including functionality of one application into another during development
/usr/lib/	Shared system libraries, e.g. libc.so (C library), libssl.so (SSL library)
/usr/lib/systemd/	Systemd service unit files
/usr/local/	Typically used to install applications compiled from source, otherwise goes largely unused
/usr/share/	Architecture-independent data files, e.g. game assets, icons, cursors, desktop themes, wallpapers, etc.
/usr/share/doc/	System documentation
/usr/share/locale/	Translations for applications
/usr/share/man/	Application manual pages
/usr/src/	Linux kernel source code files

/var Directory

The /var directory contains variable data files. These files are typically files that change frequently, such as log files, locally delivered mail and spooler files for printer job queues.

Some other examples of contents of the /var directory:

Directory/File	Description
/var/cache/	Frequently accessed data, e.g. browser cache and downloaded software packages
/var/lib/	Varying application data used by system libraries (e.g. /var/lib/libvirt/images/ for libvirt virtual machine disk images)
/var/log/	Log files of all sorts of different applications
/var/mail/	Locally delivered mail messages
/var/mysql/	MySQL database files
/var/spool/	Printer job queue

Linux File Systems

Ext4: the reliable all-rounder

Ext4 (Fourth Extended File System) is a high-performance, journaling file system widely used in Linux environments. It is an evolution of its predecessors, Ext3 and Ext2. Ext4 is the default file system for many Linux distributions, as it is battle-tested and a good choice for general purpose desktop computing needs.

Key features of Ext4 include:

1. Journaling: Like Ext3, Ext4 is a journaling file system, meaning it keeps a log (or journal) of changes to the file system before committing them to disk. This helps prevent data corruption in the event of a system crash or power failure, as the journal can be used to roll back or replay incomplete operations. Additionally, Ext4 uses checksums in the journal to improve reliability. This feature has a side benefit: it can safely avoid a disk I/O wait during journaling, improving performance slightly.
2. Larger File and Volume Support: Ext4 supports file sizes between 16 - 256 TiB and volumes up to 1 EiB, making it suitable for modern storage needs. This was a significant improvement over Ext3, which, depending on block size, was limited to 2 - 32 TiB volumes and 16 GiB - 2 TiB file sizes.
3. Extents: Extents replace the traditional block mapping scheme used by ext2 and ext3. An extent is a range of contiguous physical blocks, improving large-file performance and reducing fragmentation.
4. Backward Compatibility: Ext4 is backward compatible with Ext3, meaning you can mount an Ext3 file system as Ext4 and take advantage of the newer features without needing to reformat the partition.
5. Delayed Allocation: Ext4 provides better performance compared to Ext3, thanks to delayed allocation, which improves write performance and multi-block allocation, optimizing space usage. This further helps to reduce fragmentation.
6. Extended Attributes: Ext4 supports extended attributes, allowing additional metadata to be attached to files (e.g. security labels, file system flags, user tags). This is useful for extending file properties with arbitrary application metadata to offer advanced file management.
7. Online Defragmentation: Unlike Ext3, Ext4 provides the ability to perform online defragmentation, which allows the file system to be defragmented while the system is running, reducing the impact on performance.

Ext4 is a solid choice for every-day computing needs. It's simple, robust and well tested in the field. However, its developers have stated that Ext4 is just a stop-gap until more modern file systems like Btrfs mature and reach the same performance and robustness levels as Ext4.

Btrfs: modern and feature-packed

Btrfs (B-tree File System) is a modern, copy-on-write (COW) file system for Linux designed to address the limitations of older file systems like Ext4. It provides advanced features such as snapshots, data integrity verification, built-in volume management, and more. Btrfs aims to combine the functionalities of traditional file systems and logical volume managers, making it a versatile and powerful tool for managing storage.

Key features of Btrfs include:

1. Copy-on-Write (COW): Btrfs uses copy-on-write (COW) for data and metadata, meaning that when data is modified, the changes are written to new locations on disk instead of overwriting the original data. This approach ensures that the previous version of the data is preserved, which is crucial for features like snapshots and data integrity. It also makes copies of data on the same volume instantaneous, because both refer to the same block of data on disk. COW provides benefits such as atomic writes, where operations are either fully completed or not done at all, reducing the risk of data corruption.
2. Snapshots: Snapshots are read-only or read-write copies of the file system at a specific point in time. Snapshots are efficient and fast because they share common data blocks until changes to the data on the disk are made. Snapshots are ideal for backup, system rollback, and testing purposes. They allow you to capture the state of the file system and revert back to it later if necessary. With certain system configurations it is even possible to boot into a snapshot.
3. Data Integrity and Checksumming: Btrfs provides checksumming for both data and metadata. Every block of data and metadata is verified with a checksum when read or written. If corruption is detected (e.g. due to hardware failure), Btrfs can attempt to recover the data using its checksums. This feature significantly improves the file system's reliability, especially in environments where data integrity is critical.
4. Built-in Volume Management: Btrfs includes volume management features natively, which means it can handle multiple physical devices and manage them as a single logical volume. This feature eliminates the need for external volume managers like LVM (Logical Volume Manager). It supports RAID-like configurations (RAID 0, RAID 1, RAID 10) natively, allowing users to create storage pools with redundancy and striping.
5. Compression and Deduplication: Btrfs natively supports transparent compression, allowing data to be stored in a compressed format to save space. Several algorithms (such as LZO and zstd) are available for use. Deduplication (removal of duplicate data) can also be performed, making it ideal for environments with large amounts of redundant data where storage space is precious.
6. Dynamic Sizing and Subvolumes: Btrfs allows the dynamic resizing of file systems, making it easy to increase or decrease the size of volumes as needed, without requiring reformatting or complex migrations. Subvolumes are logical divisions of a file system that can be treated like separate file systems. Each subvolume can have its own set of snapshots, making them useful for organizing data, creating backups, or managing different applications in isolation. Subvolumes can also be used to install multiple different operating systems on the same file system without getting into the way of one another.
7. Online Defragmentation: Btrfs supports online defragmentation, meaning that it can reorganize and defragment the file system while the system is running, which can help improve performance over time, especially on systems with high churn of small files.
8. Self-healing: In combination with its checksumming capabilities, Btrfs is able to self-heal data when used with RAID configurations. For example, in a RAID 1 setup, if one disk has corrupted data, Btrfs can detect the issue and restore the correct data from the mirrored copy.

The rich feature set of Btrfs makes it a modern and versatile choice for data storage on Linux. Built-in volume management at the file system level eliminates having to think about partition layouts and sizes, while the RAID capabilities make an underlying software RAID layer redundant. Snapshots allow for quick rollbacks to a previous state of the system without wasting precious space. Transparent compression and deduplication maximize efficient use of storage space. When used effectively, Btrfs is an excellent and future-proof choice.

However, because Btrfs is still a relatively new file system, some features are still not considered ready for daily use, e.g. integrated RAID 5/6 support currently being considered unstable. It also often ranks worse than other file systems in areas where high throughput is important, such as database applications or as backing storage for virtual machines. The complex feature set may also pose a high learning curve for people unfamiliar with its concepts.

XFS: the workhorse

XFS is a high-performance journaling file system created by Silicon Graphics, Inc. for their IRIX workstations. XFS is particularly proficient at parallel I/O due to its allocation group based design. This enables extreme scalability of I/O threads, filesystem bandwidth, file and filesystem size when spanning multiple storage devices.

Key features of XFS include:

1. Journaling: Like other journaling file systems, XFS keeps a log (journal) of file system changes before they are written to disk. This helps ensure data integrity in the event of a system crash or power failure, as the file system can use the journal to recover incomplete operations.
2. Scalability: XFS is designed to handle large volumes and large files efficiently. It supports file systems as large as 16 EiB and individual file sizes up to 8 EiB, making it suitable for modern data centers and high-performance applications that require managing vast amounts of data.
3. Parallel I/O: XFS is optimized for parallel I/O operations, which improves performance for applications with heavy read/write demands like databases or large media files.
4. Extents-based Allocation: XFS uses extents (contiguous blocks of storage) to manage files, which reduces fragmentation and improves throughput when working with large files.
5. Online Defragmentation: XFS supports online defragmentation, allowing for defragmentation of the file system without having to unmount it. This is particularly useful for maintaining performance on systems with minimal downtime.
6. Dynamic Allocation: XFS supports dynamic inode allocation, meaning that inodes (the data structures used to store metadata about files) can be created as needed, improving the file system’s efficiency when dealing with a large amount of files.
7. Data Integrity: In addition to journaling, XFS also provides checksumming of metadata, which helps ensure data integrity and detect corruption. This is important for environments where data reliability is critical.
8. Efficient Space Management: XFS is known for its efficient space management. It uses techniques like delayed allocation and aggressive pre-allocation to minimize disk fragmentation and optimize disk space usage

XFS is the file system of choice when high throughput and performance are important. It's the file system of choice for storage arrays found in servers and NAS systems. It is a good choice for the backing storage for virtual machine environments and high availability database applications. While it lacks some of the advanced features found in other file systems (like snapshots or compression), it excels in areas such as scalability, performance, and data integrity. XFS is well-suited for applications requiring fast, reliable access to large datasets.

Areas that XFS does not perform well in is handling large amounts of small files, as it stays true to its data center and workstation roots. Another downside of XFS is that while it's easy to grow the file system, it is not (yet) possible to shrink it. XFS recovery, while reliable, can be more complex than other file systems in cases of severe corruption, and its repair tools are not as user-friendly as those for Ext4.

ZFS: the file system to end all file systems

ZFS (Zettabyte File System) is a high-performance, advanced file system originally developed by Sun Microsystems (now part of Oracle) for the Solaris operating system. ZFS combines both a file system and a volume manager, providing integrated management of storage. It is known for its robust features, such as data integrity, high scalability, fault tolerance, and ease of management, making it a popular choice in enterprise environments, as well as for personal use by those requiring advanced features in Linux or FreeBSD.

Key features of ZFS include:

1. Data Integrity and Checksumming: One of ZFS's standout features is its data integrity capabilities. It uses checksums for all data and metadata. Every block of data is verified when read and written, ensuring that corruption is detected and corrected. If corruption occurs (e.g. from disk errors), ZFS can automatically attempt to repair it using redundant copies or RAID-like configurations.
2. Copy-on-Write (COW): ZFS utilizes copy-on-write, meaning that when data is modified, it is not overwritten in place. Instead, new data is written to a different location, and once the write operation is complete, the system updates its pointers to the new location. This ensures that the file system always remains in a consistent state, even in the event of a power failure or system crash.
3. Snapshots: ZFS supports snapshots, which are read-only or read-write copies of the file system at a particular point in time. Snapshots are efficient in terms of storage because they only store changes made after the snapshot was taken, not the entire data set. This makes snapshots an ideal tool for rollbacks.
4. Pooled Storage: Unlike traditional file systems, ZFS combines file system and volume management, allowing it to create storage pools (called Zpools). Zpools abstract physical devices into a single logical pool of storage and data is automatically distributed across multiple devices. This allows ZFS to easily manage devices of varying sizes, providing better flexibility and redundancy. Additionally, pools can have cache devices, combinging the capacity of spinning hard drives with the speed of solid state drives to increase performance.
5. RAID-Z: ZFS includes its own RAID-like functionality, called RAID-Z, which provides data redundancy and improved performance. RAID-Z can be thought of as a more advanced version of RAID 5, with better protection against data loss due to disk failures. RAID-Z offers different configurations: RAID-Z1 (single parity), RAID-Z2 (double parity), and RAID-Z3 (triple parity), providing varying levels of fault tolerance.
6. Compression: ZFS supports inline compression, meaning that data is compressed as it is written to disk. This can significantly reduce storage space usage. ZFS supports multiple compression algorithms (e.g. LZ4, ZLE, zstd). Compression is transparent and data is automatically decompressed when read.
7. Deduplication: ZFS offers deduplication, which ensures that duplicate data is stored only once. This feature can be particularly useful in environments where many identical files are stored (e.g. backups or virtual machine images). However, deduplication can be resource-intensive and should be used with caution on systems with limited memory.
8. High Scalability: ZFS is highly scalable, supporting file systems and storage pools up to 256 trillion YiB (2¹²⁸ bytes) in size with a maximum file size of 16 EiB. It can handle vast amounts of data and large numbers of files, making it ideal for enterprise-level storage solutions and large-scale data environments.
9. Self-Healing: ZFS provides self-healing capabilities. In case of data corruption (detected through checksums), ZFS can automatically repair data by accessing redundant copies (e.g. from RAID-Z). This ensures data reliability without requiring manual intervention.

With features like data integrity, compression, snapshots, RAID-Z, and self-healing, ZFS offers exceptional storage management capabilities, making it ideal for large-scale enterprise environments and applications requiring high availability and data protection. However, its resource requirements, complexity, and limited support on non-Solaris platforms makes it diffucult to use outside of these environments. For desktop computers, other file systems are generally a better choice. For those who need enterprise-grade features and are willing to manage its complexity, ZFS is the uncontested choice.