DESCRIPTION
When, as is customary, the proc filesystem is mounted on /proc, you can find in the file /proc/filesystems which filesystems your kernel currently supports; see proc(5) for more details. There is also a legacy sysfs(2) system call (whose availability is controlled by the CONFIG_SYSFS_SYSCALL kernel build configuration option since Linux 3.15) that enables enumeration of the currently available filesystem types regardless of /proc availability and/or sanity.
If you need a currently unsupported filesystem, insert the corresponding kernel module or recompile the kernel.
In order to use a filesystem, you have to mount it; see mount(2) and mount(8).
The following list provides a short description of the available or historically available filesystems in the Linux kernel. See the kernel documentation for a comprehensive description of all options and limitations.
ext is an elaborate extension of the minix filesystem. It has been completely superseded by the second version of the extended filesystem (ext2) and has been removed from the kernel (in Linux 2.1.21). ext2 is a disk filesystem that was used by Linux for fixed disks as well as removable media. The second extended filesystem was designed as an extension of the extended filesystem (ext). See ext2(5). ext3 is a journaling version of the ext2 filesystem. It is easy to switch back and forth between ext2 and ext3. See ext3(5). ext4 is a set of upgrades to ext3 including substantial performance and reliability enhancements, plus large increases in volume, file, and directory size limits. See ext4(5). hpfs is the High Performance Filesystem, used in OS/2. This filesystem is read-only under Linux due to the lack of available documentation. iso9660 is a CD-ROM filesystem type conforming to the ISO 9660 standard.
High Sierra Linux supports High Sierra, the precursor to the ISO 9660 standard for CD-ROM filesystems. It is automatically recognized within the iso9660 filesystem support under Linux. Rock Ridge Linux also supports the System Use Sharing Protocol records specified by the Rock Ridge Interchange Protocol. They are used to further describe the files in the iso9660 filesystem to a UNIX host, and provide information such as long filenames, UID/GID, POSIX permissions, and devices. It is automatically recognized within the iso9660 filesystem support under Linux.
JFS is a journaling filesystem, developed by IBM, that was integrated into Linux 2.4.24. minix is the filesystem used in the Minix operating system, the first to run under Linux. It has a number of shortcomings, including a 64 MB partition size limit, short filenames, and a single timestamp. It remains useful for floppies and RAM disks. msdos is the filesystem used by DOS, Windows, and some OS/2 computers. msdos filenames can be no longer than 8 characters, followed by an optional period and 3 character extension. ncpfs is a network filesystem that supports the NCP protocol, used by Novell NetWare. It was removed from the kernel in Linux 4.17. To use ncpfs, you need special programs, which can be found at ftp://ftp.gwdg.de/pub/linux/misc/ncpfs. nfs is the network filesystem used to access disks located on remote computers. ntfs is the filesystem native to Microsoft Windows NT, supporting features like ACLs, journaling, encryption, and so on. proc is a pseudo filesystem which is used as an interface to kernel data structures rather than reading and interpreting /dev/kmem. In particular, its files do not take disk space. See proc(5). Reiserfs is a journaling filesystem, designed by Hans Reiser, that was integrated into Linux 2.4.1. smb is a network filesystem that supports the SMB protocol, used by Windows. See https://www.samba.org/samba/smbfs/. sysv is an implementation of the System V/Coherent filesystem for Linux. It implements all of Xenix FS, System V/386 FS, and Coherent FS. umsdos is an extended DOS filesystem used by Linux. It adds capability for long filenames, UID/GID, POSIX permissions, and special files (devices, named pipes, etc.) under the DOS filesystem, without sacrificing compatibility with DOS. tmpfs is a filesystem whose contents reside in virtual memory. Since the files on such filesystems typically reside in RAM, file access is extremely fast. See tmpfs(5). vfat is an extended FAT filesystem used by Microsoft Windows95 and Windows NT. vfat adds the capability to use long filenames under the MSDOS filesystem. XFS is a journaling filesystem, developed by SGI, that was integrated into Linux 2.4.20. xiafs was designed and implemented to be a stable, safe filesystem by extending the Minix filesystem code. It provides the basic most requested features without undue complexity. The xiafs filesystem is no longer actively developed or maintained. It was removed from the kernel in Linux 2.1.21.
SEE ALSO
Package name: core/man-pages Version: 6.04-1 Upstream: https://www.kernel.org/doc/man-pages/ Licenses: GPL, custom Manuals: /listing/core/man-pages/ Table of contents
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DESCRIPTION
The sysfs filesystem is a pseudo-filesystem which provides an interface to kernel data structures. (More precisely, the files and directories in sysfs provide a view of the kobject structures defined internally within the kernel.) The files under sysfs provide information about devices, kernel modules, filesystems, and other kernel components.
The sysfs filesystem is commonly mounted at /sys. Typically, it is mounted automatically by the system, but it can also be mounted manually using a command such as:
Many of the files in the sysfs filesystem are read-only, but some files are writable, allowing kernel variables to be changed. To avoid redundancy, symbolic links are heavily used to connect entries across the filesystem tree.
Files and directories
The following list describes some of the files and directories under the /sys hierarchy.
/sys/block This subdirectory contains one symbolic link for each block device that has been discovered on the system. The symbolic links point to corresponding directories under /sys/devices. /sys/bus This directory contains one subdirectory for each of the bus types in the kernel. Inside each of these directories are two subdirectories:
devices This subdirectory contains symbolic links to entries in /sys/devices that correspond to the devices discovered on this bus. drivers This subdirectory contains one subdirectory for each device driver that is loaded on this bus.
/sys/class This subdirectory contains a single layer of further subdirectories for each of the device classes that have been registered on the system (e.g., terminals, network devices, block devices, graphics devices, sound devices, and so on). Inside each of these subdirectories are symbolic links for each of the devices in this class. These symbolic links refer to entries in the /sys/devices directory. /sys/class/net Each of the entries in this directory is a symbolic link representing one of the real or virtual networking devices that are visible in the network namespace of the process that is accessing the directory. Each of these symbolic links refers to entries in the /sys/devices directory. /sys/dev This directory contains two subdirectories block/ and char/, corresponding, respectively, to the block and character devices on the system. Inside each of these subdirectories are symbolic links with names of the form major-ID:minor-ID, where the ID values correspond to the major and minor ID of a specific device. Each symbolic link points to the sysfs directory for a device. The symbolic links inside /sys/dev thus provide an easy way to look up the sysfs interface using the device IDs returned by a call to stat(2) (or similar). The following shell session shows an example from /sys/dev:
$ stat -c "%t %T" /dev/null 1 3 $ readlink /sys/dev/char/1\:3 ../../devices/virtual/mem/null $ ls -Fd /sys/devices/virtual/mem/null /sys/devices/virtual/mem/null/ $ ls -d1 /sys/devices/virtual/mem/null/* /sys/devices/virtual/mem/null/dev /sys/devices/virtual/mem/null/power/ /sys/devices/virtual/mem/null/subsystem@ /sys/devices/virtual/mem/null/uevent
/sys/devices This is a directory that contains a filesystem representation of the kernel device tree, which is a hierarchy of device structures within the kernel. /sys/firmware This subdirectory contains interfaces for viewing and manipulating firmware-specific objects and attributes. /sys/fs This directory contains subdirectories for some filesystems. A filesystem will have a subdirectory here only if it chose to explicitly create the subdirectory. /sys/fs/cgroup This directory conventionally is used as a mount point for a tmpfs(5) filesystem containing mount points for cgroups(7) filesystems. /sys/fs/smackfs The directory contains configuration files for the SMACK LSM. See the kernel source file Documentation/admin-guide/LSM/Smack.rst. /sys/hypervisor [To be documented] /sys/kernel This subdirectory contains various files and subdirectories that provide information about the running kernel. /sys/kernel/cgroup/ For information about the files in this directory, see cgroups(7). /sys/kernel/debug/tracing Mount point for the tracefs filesystem used by the kernel’s ftrace facility. (For information on ftrace, see the kernel source file Documentation/trace/ftrace.txt.) /sys/kernel/mm This subdirectory contains various files and subdirectories that provide information about the kernel’s memory management subsystem. /sys/kernel/mm/hugepages This subdirectory contains one subdirectory for each of the huge page sizes that the system supports. The subdirectory name indicates the huge page size (e.g., hugepages-2048kB). Within each of these subdirectories is a set of files that can be used to view and (in some cases) change settings associated with that huge page size. For further information, see the kernel source file Documentation/admin-guide/mm/hugetlbpage.rst. /sys/module This subdirectory contains one subdirectory for each module that is loaded into the kernel. The name of each directory is the name of the module. In each of the subdirectories, there may be following files:
coresize [to be documented] initsize [to be documented] initstate [to be documented] refcnt [to be documented] srcversion [to be documented] taint [to be documented] uevent [to be documented] version [to be documented]
drivers [To be documented] holders [To be documented] notes [To be documented] parameters This directory contains one file for each module parameter, with each file containing the value of the corresponding parameter. Some of these files are writable, allowing the sections This subdirectories contains files with information about module sections. This information is mainly used for debugging. [To be documented]