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Hub AI
Filesystem Hierarchy Standard AI simulator
(@Filesystem Hierarchy Standard_simulator)
Hub AI
Filesystem Hierarchy Standard AI simulator
(@Filesystem Hierarchy Standard_simulator)
Filesystem Hierarchy Standard
The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of Unix-like systems. It has been made popular by its use in Linux distributions, but it is used by other Unix-like systems as well. The latest version of the standard, version 3.0, was originally released on 3 June 2015 by the Linux Foundation. It was republished on 6 November 2025 by FreeDesktop, which has since assumed maintenance of the specification.
In the FHS, all files and directories appear under the root directory /, even if they are stored on different physical or virtual devices. Some of these directories only exist in a particular system if certain subsystems, such as the X Window System, are installed.
Most of these directories exist in all Unix-like operating systems and are generally used in much the same way; however, the descriptions here are those used specifically for the FHS and are not considered authoritative for platforms other than Linux.
Most Linux distributions follow the Filesystem Hierarchy Standard and declare it their own policy to maintain FHS compliance. GoboLinux and NixOS provide examples of intentionally non-compliant filesystem implementations.
Some distributions generally follow the standard but deviate from it in some areas. The FHS is a "trailing standard", and so documents common practices at a point in time. Of course, times change, and distribution goals and needs call for experimentation. Some common deviations include:
Modern Linux distributions include a /run directory as a temporary filesystem (tmpfs), which stores volatile runtime data, following the FHS version 3.0. According to the FHS version 2.3, such data were stored in /var/run, but this was a problem in some cases because this directory is not always available at early boot. As a result, these programs have had to resort to workarounds, such as using /dev/.udev, /dev/.mdadm, /dev/.systemd or /dev/.mount directories, even though the device directory is not intended for such data. Among other advantages, this makes the system easier to use normally with the root filesystem mounted read-only.
For example, below are the changes Debian made in its 2013 Wheezy release:
FHS was created as the FSSTND (short for "Filesystem Standard"), largely based on similar standards for other Unix-like operating systems, such as the Version 7 Unix hier(7) from 1979, the SunOS 4.x filesystem(7) and its successor, the Solaris filesystem(7), and the FreeBSD hier(7).
Filesystem Hierarchy Standard
The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of Unix-like systems. It has been made popular by its use in Linux distributions, but it is used by other Unix-like systems as well. The latest version of the standard, version 3.0, was originally released on 3 June 2015 by the Linux Foundation. It was republished on 6 November 2025 by FreeDesktop, which has since assumed maintenance of the specification.
In the FHS, all files and directories appear under the root directory /, even if they are stored on different physical or virtual devices. Some of these directories only exist in a particular system if certain subsystems, such as the X Window System, are installed.
Most of these directories exist in all Unix-like operating systems and are generally used in much the same way; however, the descriptions here are those used specifically for the FHS and are not considered authoritative for platforms other than Linux.
Most Linux distributions follow the Filesystem Hierarchy Standard and declare it their own policy to maintain FHS compliance. GoboLinux and NixOS provide examples of intentionally non-compliant filesystem implementations.
Some distributions generally follow the standard but deviate from it in some areas. The FHS is a "trailing standard", and so documents common practices at a point in time. Of course, times change, and distribution goals and needs call for experimentation. Some common deviations include:
Modern Linux distributions include a /run directory as a temporary filesystem (tmpfs), which stores volatile runtime data, following the FHS version 3.0. According to the FHS version 2.3, such data were stored in /var/run, but this was a problem in some cases because this directory is not always available at early boot. As a result, these programs have had to resort to workarounds, such as using /dev/.udev, /dev/.mdadm, /dev/.systemd or /dev/.mount directories, even though the device directory is not intended for such data. Among other advantages, this makes the system easier to use normally with the root filesystem mounted read-only.
For example, below are the changes Debian made in its 2013 Wheezy release:
FHS was created as the FSSTND (short for "Filesystem Standard"), largely based on similar standards for other Unix-like operating systems, such as the Version 7 Unix hier(7) from 1979, the SunOS 4.x filesystem(7) and its successor, the Solaris filesystem(7), and the FreeBSD hier(7).