Filesystem
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A filesystem is a means to organize data to be retained after a program terminates. Filesystems provide procedures to store, retrieve, and update data, as well as to manage the available space on the device(s) which contain it.
Linux has a few dozen filesystems available, each with their own advantages and disadvantages when considering a particular use case.
Filesystems
General information
- Filesystem/Access Control List Guide — an additional security control feature for multiuser systems.
- Filesystem/Security — one of the basic means to harden a system.
Flash memory filesystems
The following flash memory filesystems are designed to be used on embedded flash memory known as MTDs; they are not intended to be used for USB based flash drives, SD cards, or other types of removable flash block devices.
| Name | Userspace package | Description |
|---|---|---|
| JFFS2 | Journalling Flash File System version 2. | |
| YAFFS | sys-fs/yaffs2utils | Yet Another Flash File System. |
Disk filesystems
| Name | Userspace package | Description |
|---|---|---|
| bcachefs | sys-fs/bcachefs-tools | A next generation, robust, high performance filesystem supporting CoW (Copy-on-write), compression, and encryption. |
| btrfs | sys-fs/btrfs-progs | A copy-on-write B-tree file system (btrfs) with advanced features. |
| Cramfs | sys-fs/cramfs | A memory and space sensitive compressed filesystem that supports random reading. It avoids the block device layer and usefulness in tiny embedded systems with very tight memory constraints. |
| eCryptfs | sys-fs/ecryptfs-utils | The enterprise cryptographic filesystem for Linux. |
| efivarfs | A (U)EFI variable filesystem[1] | |
| exFAT | sys-fs/exfatprogs | Extensible File Allocation Table (exFAT) filesystem by Microsoft, natively supported since Linux 5.7[2] |
| ext4 | sys-fs/e2fsprogs | The default, GPL licensed journaling filesystem for many Linux distributions. |
| F2FS | sys-fs/f2fs-tools | A Flash-Friendly File System (F2FS) created by Samsung for the Linux kernel. |
| FAT | sys-fs/dosfstools | The File Allocation Table (FAT) filesystem. Originally created for use with Microsoft Windows. |
| GFS2 | Global File System 2: A shared disk filesystem. Typically used in compute clusters. | |
| HFS | sys-fs/hfsutils | Hierarchical File System (HFS). Originally created for use with the Macintosh System Software, later renamed to Mac OS (Classic). |
| HFS+ | sys-fs/hfsplusutils | The successor to HFS, introduced in Mac OS 8.1 and default filesystem for Mac OS X until macOS 10.12 Sierra. |
| JFS | sys-fs/jfsutils | A GPL licensed, 64-bit Journaled File System (JFS) developed by IBM.[3] |
| NILFS | sys-fs/nilfs-utils | A log-structured file system implementation for the Linux kernel. |
| NTFS | Microsoft Windows' New Technology File System (NTFS) (Windows' default filesystem). | |
| OCFS2 | Oracle Cluster File System version 2. | |
| OverlayFS | The only union-like filesystem built-in to the Linux kernel. | |
| ReiserFS | sys-fs/reiserfsprogs | Version 3 of the ReiserFS filesystem. Scheduled for removal from the kernel in 2025. |
| SquashFS | sys-fs/squashfs-tools, sys-fs/squashfs-tools-ng | A compressed, read-only file system for Linux[4] |
| UDF | sys-fs/udftools | Universal Disk Format - needed for mounting some kind of .iso files |
| UFS | The Unix File System (UFS) also called the Berkeley Fast File System. | |
| XFS | sys-fs/xfsprogs | A GPL licensed, 64-bit journaling filesystem created by Silicon Graphics.[5] |
| ZFS | sys-fs/zfs | A CDDL (non-GPL compatible) licensed, copy-on-write filesystem created by Sun Microsystems[6]. |
Virtual filesystems
Virtual filesystems, also called pseudo filesystems, are for storing temporary data in memory while the system is running.
| Name | Userspace package | Description |
|---|---|---|
| debugfs | Used for debugging purposes; primarily Linux kernel development. | |
| procfs | Used to output and change of system and process information. | |
| securityfs | Used by the TPM BIOS character driver, AppArmor and IMA, an integrity provider.[7] | |
| sysfs | Used to output information about and to configure devices and drivers. | |
| tmpfs | Used to store files in memory (RAM). | |
| devtmpfs | udev requires devtmpfs (Maintain a devtmpfs filesystem to mount at /dev) in the kernel. |
Network filesystems
| Name | Userspace package | Description |
|---|---|---|
| Ceph | sys-cluster/ceph | A distributed object store and filesystem designed to provide excellent performance, reliability, and scalability. |
| GlusterFS | sys-cluster/glusterfs | A powerful network/cluster filesystem. |
| NFS | net-fs/nfs-utils | A common Linux network file system protocol. |
| Samba | net-fs/samba | A re-implementation of the SMB/CIFS networking protocol. |
FUSE-based filesystems
| Name | Userspace package | Description |
|---|---|---|
| CurlFtpFS | net-fs/curlftpfs | File system for accessing FTP hosts based on FUSE. |
| FuseISO | sys-fs/fuseiso | FUSE module to mount ISO filesystem images. |
| MTPfs | sys-fs/mtpfs | A FUSE filesystem providing access to Media Transfer Protocol (MTP) devices. |
| smbnetfs | net-fs/smbnetfs | A FUSE filesystem for SMB shares. |
| SSHFS | net-fs/sshfs | Implements FUSE to mount filesystems in user space. |
| squashfuse | sys-fs/squashfuse | Mount SquashFS archives using FUSE. |
Usage
Mounting
Filesystems can be mounted in several ways:
- mount - The command used to mount filesystems. Requires administrative privileges or entries in /etc/fstab.
- /etc/fstab - Contains descriptive information about the filesystems the system can mount.
- Removable media - Mount on file demand.
- Udevil - A small auto-mount utility with little dependencies.
- AutoFS - Automatic mount on file access.
See also
- Bcache — a Linux kernel block layer cache.
- Filesystem security — one of the basic means to harden a system.
- Filesystem in Userspace — a way for users to mount file systems without needing special permissions
- Filesystems in Handbook AMD64
External resources
- Linux Sea, by Sven Vermeulen, chapter about filesystems
- Bitrot and atomic COWs: Inside “next-gen” filesystems (Ars Technica)
- A Study of Linux File System Evolution (PDF document from USENIX)