File systems

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From Wikipedia:

In computing, a file system (or filesystem) is used to control how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops and the next begins. By separating the data into pieces and giving each piece a name, the information is easily isolated and identified.
Taking its name from the way paper-based information systems are named, each group of data is called a "file". The structure and logic rules used to manage the groups of information and their names is called a "file system".

Individual drive partitions can be setup using one of the many different available filesystems. Each has its own advantages, disadvantages, and unique idiosyncrasies. A brief overview of supported filesystems follows; the links are to Wikipedia pages that provide much more information.

Create a file system

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Reason: It is also possible to create a file system on an actual file, e.g. to access VMs from the host (Discuss in Talk:File systems#)
Note: A drive must be partitioned before creating file systems.

Identify the device where the file system will be created, for example with lsblk:

$ lsblk -f

File systems are usually created on a partition, but they can also be created inside of logical containers like LVM, RAID, or dm-crypt.

To create a new file system on a partition, the existing file system located on the partition must not be mounted. If the partition you want to format contains a mounted filesystem, it will show up in the MOUNTPOINT column of lsblk.

To unmount it, you can use umount on the directory where the filesystem was mounted to:

# umount /mountpoint

To create a new file system of type fstype on a partition do:

Warning: After creating a new filesystem, data previously stored on this partition can likely not be recovered. Make a backup of any data you want to keep.
# mkfs.fstype /dev/partition

See the article in #Types of file systems corresponding to file system you wish to create for the exact command as well as userspace utilities you may wish to install for a particular file system.

For example, to create a new file system of type ext4 on a partition, run:

# mkfs.ext4 /dev/partition

Types of file systems

See also w:Comparison_of_file_systems.

  • Btrfs — the B-tree file system is "a new copy on write (CoW) filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, repair and easy administration." [1] It has been merged into the mainline kernel Btrfs and has a stable filesystem disk format. [2] || btrfs-progs
  • VFATVirtual File Allocation Table is technically simple and supported by virtually all existing operating systems. This makes it a useful format for solid-state memory cards and a convenient way to share data between operating systems. VFAT supports long file names. || dosfstools
  • exFATMicrosoft file system optimized for flash drives. Like NTFS, exFAT can pre-allocate disk space for a file by just marking arbitrary space on disk as 'allocated'. || exfat-utils
  • F2FSFlash-Friendly File System is a flash file system created by Kim Jaegeuk (Hangul: 김재극) at Samsung for the Linux operating system kernel. The motivation for F2FS was to build a file system which takes into account the characteristics of NAND flash memory-based storage devices (such as solid-state disks, eMMC, and SD cards). || f2fs-tools
  • extSecond Extended Filesystem does not have journaling support or barriers. Lack of journaling can result in data loss in the event of a power failure or system crash. When used on larger partitions, file/system checks may take a long time. An ext2 filesystem can be converted to ext3. Third Extended Filesystem is essentially the ext2 system with journaling support and write barriers. It is backward compatible with ext2. Fourth Extended Filesystem is a newer filesystem that is also compatible with ext2 and ext3. It provides support for volumes with sizes up to 1 exabyte (i.e. 1,048,576 terabytes) and files sizes up to 16 terabytes. It increases the 32,000 subdirectory limit in ext3 to unlimited. It also offers online defragmentation capability. || e2fsprogs
  • HFSHierarchical File System is a proprietary file system developed by Apple Inc. for use in computer systems running Mac OS. || hfsprogs
  • JFS — IBM's Journaled File System was the first filesystem to offer journaling. It was developed in the IBM AIX® operating system before being ported to GNU/Linux. || jfsutils
  • NILFS2New Implementation of a Log-structured File System was developed by NTT. It records all data in a continuous log-like format that is only appended to and never overwritten. It is designed to reduce seek times and minimize the type of data loss that occurs after a crash with conventional Linux filesystems. || nilfs-utils
  • NTFSFile system used by Windows. NTFS has several technical improvements over FAT and HPFS (High Performance File System), such as improved support for metadata, and the use of advanced data structures to improve performance, reliability, and disk space utilization, plus additional extensions, such as security access control lists (ACL) and file system journaling. || ntfs-3g
  • Reiser4Successor to the ReiserFS file system, developed from scratch by Namesys and sponsored by DARPA as well as Linspire, it uses B*-trees in conjunction with the dancing tree balancing approach, in which underpopulated nodes will not be merged until a flush to disk except under memory pressure or when a transaction completes. Such a system also allows Reiser4 to create files and directories without having to waste time and space through fixed blocks. || reiser4progsAUR
  • ReiserFSHans Reiser's high-performance journaling FS (v3) is touted as very fast, especially when dealing with many small files. ReiserFS is fast at formatting, yet comparatively slow at mounting. ReiserFSv3 is not being actively developed at this time. Generally regarded as a good choice for /var. || reiserfsprogs
  • XFSEarly journaling filesystem originally developed by Silicon Graphics for the IRIX operating system and ported to GNU/Linux. It provides very fast throughput on large files and filesystems and is very fast at formatting and mounting. Comparative benchmark testing has shown it to be slower when dealing with many small files. XFS is very mature and offers online defragmentation capability. || xfsprogs
  • ZFSCombined file system and logical volume manager designed by Sun Microsystems. The features of ZFS include protection against data corruption, support for high storage capacities, integration of the concepts of filesystem and volume management, snapshots and copy-on-write clones, continuous integrity checking and automatic repair, RAID-Z and native NFSv4 ACLs. || zfs-linuxAUR, zfs-linux-gitAUR


All the above filesystems with the exception of ext2, FAT16/32, use journaling. Journaling provides fault-resilience by logging changes before they are committed to the filesystem. In the event of a system crash or power failure, such file systems are faster to bring back online and less likely to become corrupted. The logging takes place in a dedicated area of the filesystem.

Not all journaling techniques are the same. Ext3 and ext4 offer data-mode journaling, which logs both data and meta-data, as well as possibility to journal only meta-data changes. Data-mode journaling comes with a speed penalty and is not enabled by default. In the same vein, Reiser4 offers so-called "transaction models", which include pure journaling (equivalent to ext4's data-mode journaling), pure Copy-on-Write approach (equivalent to btrfs' default) and a combined approach which heuristically alternates between the two former. It should be noted that reiser4 does not provide an equivalent to ext4's default journaling behavior (meta-data only).

The other filesystems provide ordered-mode journaling, which only logs meta-data. While all journaling will return a filesystem to a valid state after a crash, data-mode journaling offers the greatest protection against corruption and data loss. There is a compromise in system performance, however, because data-mode journaling does two write operations: first to the journal and then to the disk. The trade-off between system speed and data safety should be considered when choosing the filesystem type.

FUSE-based file systems

Filesystem in Userspace (FUSE) is a mechanism for Unix-like operating systems that lets non-privileged users create their own file systems without editing kernel code. This is achieved by running file system code in user space, while the FUSE kernel module provides only a "bridge" to the actual kernel interfaces.

Some FUSE-based file systems:

  • acd-fuse — FUSE filesystem driver for Amazon's Cloud Drive. || acdfuse-gitAUR[broken link: archived in aur-mirror]
  • adbfs-git — Mount an Android device filesystem. || adbfs-gitAUR
  • cddfs — Mount audio CDs. || cddfsAUR[broken link: archived in aur-mirror]
  • fuseiso — Mount an ISO as a regular user. || fuseiso
  • vdfuse — Mounting VirtualBox disk images (VDI/VMDK/VHD). || vdfuseAUR
  • wiifuse — Mount a Gamecube or Wii DVD disc image read-only. || wiifuseAUR[broken link: archived in aur-mirror]
  • xbfuse-git — Mount an Xbox (360) ISO. || xbfuse-gitAUR
  • xmlfs — Represent an XML file as a directory structure for easy access. || xmlfsAUR || zfs-fuseAUR[broken link: archived in aur-mirror]
  • EncFS — EncFS is a userspace stackable cryptographic file-system. || encfs
  • gitfs — gitfs is a FUSE file system that fully integrates with git. || gitfsAUR

See Wikipedia:Filesystem in Userspace#Example uses for more.

Special purpose file systems

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Reason: Ambiguous section name, c.f. [3]. (Discuss in Talk:File systems#)
  • CramFSCompressed ROM filesystem is a read only filesystem designed with simplicity and efficiency in mind. Its maximum file size is less 16MB and the maximum file system size is around 272MB. || util-linux
  • eCryptfsEnterprise Cryptographic Filesystem is a package of disk encryption software for Linux. It is implemented as a POSIX-compliant filesystem-level encryption layer, aiming to offer functionality similar to that of GnuPG at the operating system level. || ecryptfs-utils
  • SquashFSSquashFS is a compressed read only filesystem. SquashFS compresses files, inodes and directories, and supports block sizes up to 1 MB for greater compression. || squashfs-tools