fstab (after ''
file systems table'') is a
system file
A system file in computers is a critical computer file without which a computer system may not operate correctly. These files may come as part of the operating system, a third-party device driver or other sources. Microsoft Windows and MS-DOS mark ...
commonly found in the directory
/etc
on
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
and
Unix-like
A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...
computer systems. The
/etc/fstab
file is used by utilities from the
util-linux
package (such as
mount
and
findmnt
), but it's not limited to them — it is also processed by
systemd
via
systemd-fstab-generator
for automatic mounting during boot. The fstab file typically lists all available disk
partitions and other types of file systems and data sources that may not necessarily be disk-based, and indicates how they are to be initialized or otherwise integrated into the larger
file system structure.
The fstab file is read by the
mount
Mount is often used as part of the name of specific mountains, e.g. Mount Everest.
Mount or Mounts may also refer to:
Places
* Mount, Cornwall, a village in Warleggan parish, England
* Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, ...
command, which happens automatically at boot time to determine the overall file system structure, and thereafter when a user executes the
mount
command to modify that structure. It is the duty of the
system administrator
An IT administrator, system administrator, sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as Server (computing), servers. The ...
to properly create and maintain the fstab file.
While fstab is used for basic system configuration, for other uses, it has been superseded by automatic mounting mechanisms.
The file has other names on some versions of
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
; for example, it is found at
/etc/vfstab
on
Solaris
Solaris is the Latin word for sun.
It may refer to:
Arts and entertainment Literature, television and film
* ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem
** ''Solaris'' (1968 film), directed by Boris Nirenburg
** ''Sol ...
systems.
Modern use
The fstab file is read by programs that work with disk partitions and other file systems and is not automatically maintained. Instead it is written by the system administrator or sometimes by an operating system installation program. However, some administration tools can automatically build and edit fstab, or act as graphical editors for it.
Modern Linux systems use
udev
udev (userspace ) is a device manager for the Linux kernel. As the successor of devfsd and hotplug, udev primarily manages device nodes in the directory. At the same time, udev also handles all user space events raised when hardware devices ...
as an
automounter
An automounter is any program or software facility which automatically mount (computing), mounts filesystems in response to access operations by user programs. An automounter system utility (Daemon (computer software), daemon under Unix), when not ...
to handle the
hot swapping
Hot swapping is the replacement or addition of components to a computer system without stopping, shutting down, or rebooting the system. Hot plugging describes only the addition of components to a running computer system. Components which ha ...
of devices (such as MP3 players or digital cameras) instead of relying on fstab. Programs such as
pmount allow ordinary users to
mount
Mount is often used as part of the name of specific mountains, e.g. Mount Everest.
Mount or Mounts may also refer to:
Places
* Mount, Cornwall, a village in Warleggan parish, England
* Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, ...
and unmount filesystems without a corresponding fstab entry; traditional Unix has always allowed privileged users (the
root user
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the ...
and users in the
wheel group) to mount or unmount devices without a corresponding fstab entry.
Example
The following is an example of an fstab file on a typical
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
system.
# device-spec mount-point fs-type options dump pass
LABEL=/ / ext4 defaults 1 1
/dev/sda6 none swap defaults 0 0
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
# Removable media
/dev/cdrom /mnt/cdrom udf,iso9660 noauto,owner,ro 0 0
# NTFS Windows 7 partition
/dev/sda1 /mnt/Windows ntfs-3g quiet,defaults,locale=en_US.utf8,umask=0,noexec 0 0
# Partition shared by Windows and Linux
/dev/sda7 /mnt/shared vfat umask=000 0 0
# Mounting tmpfs
tmpfs /mnt/tmpfschk tmpfs size=100m 0 0
# Mounting cifs
//cifs_name/store /store/pingu cifs credentials=/root/smbpass.txt 0 0
# Mounting NFS
nfs_name:/store /store nfs rw 0 0
The order of records in fstab is important because fsck(8), mount(8), and umount(8) sequentially iterate through fstab and mount in the order defined.
Blank lines and comment lines beginning with a "#" are ignored.
The space or tab-separated fields within each row must appear in a specific order:
# ''device-spec'' – The device name, label,
UUID
A Universally Unique Identifier (UUID) is a 128-bit nominal number, label used to uniquely identify objects in computer systems. The term Globally Unique Identifier (GUID) is also used, mostly in Microsoft systems.
When generated according to the ...
, or other means of specifying the partition or data source this entry refers to.
# ''mount-point'' – Where the contents of the device may be accessed after
mount
Mount is often used as part of the name of specific mountains, e.g. Mount Everest.
Mount or Mounts may also refer to:
Places
* Mount, Cornwall, a village in Warleggan parish, England
* Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, ...
ing; for
swap partitions or files, this is set to
none
.
# ''fs-type'' – The type of file system to be mounted.
# ''options'' – Options describing various other aspects of the file system, such as whether it is automatically mounted at boot, which users may mount or access it, whether it may be written to or only read from, its size, and so forth; the special option
defaults
refers to a pre-determined set of options depending on the file system type.
# ''dump'' – A number indicating whether and how often the file system should be
backed up by the
dump
Deoxyuridine monophosphate (dUMP), also known as deoxyuridylic acid or deoxyuridylate in its conjugate acid and conjugate base forms, respectively, is a deoxynucleotide.
It is an intermediate in the metabolism of deoxyribonucleotides. Biosynthes ...
program; a zero indicates the file system will never be automatically backed up.
# ''pass'' – A number indicating the order in which the
fsck
The system utility fsck (''file system check'') is a tool for checking the consistency of a file system in Unix and Unix-like operating systems, such as Linux
Linux ( ) is a family of open source Unix-like operating systems based on the L ...
program will check the devices for errors at boot time:
::
Missing values in the last two fields are interpreted as zeros. If necessary,
space character
A whitespace character is a character data element that represents white space when text is
rendered for display by a computer.
For example, a ''space'' character (, ASCII 32) represents blank space such as a word divider in a Western scri ...
s in the first, second, and fourth fields are indicated by .
Options common to all filesystems
;
auto
/
noauto
: With the
auto
option, the device will be mounted automatically at bootup or when the mount -a command is issued.
auto
is the default option. For the device not to be mounted automatically, the
noauto
option is used in /etc/fstab. With
noauto
, the device can be only mounted explicitly.
;
dev
/
nodev
: Controls behavior of the interpretation of block special devices on the filesystem.
;
exec
/
noexec
:
exec
lets binaries that are on the partition be executed, whereas
noexec
is the opposite.
noexec
might be useful for a partition that contains no binaries, like /var, or contains binaries the user may not want to execute on the system, or that cannot even be executed on the system, as might be the case of a Windows partition.
;
rw
/
ro
: Mount the filesystem in either read write or read only mode. Explicitly defining a file system as
rw
can alleviate some problems in file systems that default to read only, as can be the case with floppies or
NTFS
NT File System (NTFS) (commonly called ''New Technology File System'') is a proprietary journaling file system developed by Microsoft in the 1990s.
It was developed to overcome scalability, security and other limitations with File Allocation Tabl ...
partitions.
;
sync
/
async
: How the input and output to the filesystem should be done.
sync
means it is done synchronously. Looking at the example fstab, this is the option used with the floppy. This means that when, for example, a file is copied to the floppy, the changes are physically written to the floppy at the same time copy command is issued.
;
suid
/
nosuid
: Controls the behavior of the operation of
suid, and
sgid bits.
;
user
/
users
/
nouser
:
user
permits any user to mount the filesystem. This automatically implies
noexec
,
nosuid
,
nodev
unless explicitly overridden. If
nouser
is specified, only
root
In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...
can mount the filesystem. If
users
is specified, every user in group ''users'' will be able to unmount the volume.
;
defaults
: Use default settings. Default settings are defined per file system at the file system level. For
ext3
ext3, or third extended filesystem, is a journaling file system, journaled file system that is commonly used with the Linux kernel. It used to be the default file system for many popular Linux distributions but generally has been supplanted by ...
file systems these can be set with the ''tune2fs'' command. The normal default for
ext3
ext3, or third extended filesystem, is a journaling file system, journaled file system that is commonly used with the Linux kernel. It used to be the default file system for many popular Linux distributions but generally has been supplanted by ...
file systems is equivalent to
rw,suid,dev,exec,auto,nouser,async
. Modern Red Hat based systems set
ACL support as default on the root file system but not on user-created ext3 filesystems. Some file systems such as
XFS
XFS is a high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; a ...
enable ACLs by default. Default file system mount attributes can be overridden in /etc/fstab.
;
owner
(Linux-specific)
: Permit the owner of device to mount.
;
nofail
: Do not stop system boot if disk mount failed.
;
atime
/
noatime
/
relatime
/
strictatime
(Linux-specific)
:The Unix
stat structure records when files are last accessed (''atime''), modified (mtime), and changed (''ctime''). One result is that
atime is written every time a file is read, which has been heavily criticized for causing performance degradation and increased wear. However, atime is used by some applications and desired by some users, and thus is configurable as atime ''(update on access)'', noatime ''(do not update)'', or (in Linux) relatime ''(update atime if older than mtime)''. Through Linux 2.6.29, ''atime'' was the default; as of 2.6.30, ''relatime'' is the default.
Linux 2 6 30
at Linux Kernel Newbies
Filesystem-specific options
There are many options for the specific filesystems supported by mount
. Listed below are some of the more commonly used. The full list may be found in the documentation for mount. Note that these are for Linux; traditional Unix-like
A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...
systems have generally provided similar functionality but with slightly different syntax or forms.
ext2
; check= one, normal, strict/code>
: Sets the fsck checking level.
; debug
: Print debugging info on each remount.
; sb=n
: n
is the block
Block or blocked may refer to:
Arts, entertainment and media Broadcasting
* Block programming, the result of a programming strategy in broadcasting
* W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...
which should be used as the super-block for the filesystem.
FAT-only
; check= (elaxed), n(ormal), s(trict)/code>
: Policy for allowed filenames. See mount(8)
.
; conv= (inary), t(ext), a(uto)/code>
: Performs DOS <=> UNIX text file conversions automatically. See mount(8)
.
FAT, NTFS
; windows_names
: Linux filesystems have a larger set of allowed characters in filenames. windows_names
restricts the set of allowed characters for the volume to only those acceptable by Windows; though FAT/NTFS are the most common use cases, this feature is not specifically restricted to those filesystem types.
; uid=n
, gid=n
: Sets the user identifier ( uid), and group identifier ( gid) for all files on the filesystem.
; umask=nnn, dmask=nnn, fmask=nnn
: Controls masking of filesystem nodes.
::
More detailed information about the fstab file can be found in the man page
A man page (short for manual page) is a form of software documentation found on Unix and Unix-like operating systems. Topics covered include programs, system libraries, system calls, and sometimes local system details. The local host administr ...
fo
Linux fstab
for other systems see below.
NFS
; addr=ip
: ip
is a valid IP address
An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...
.
See also
* mount (computing)
Mounting is a process by which a computer's operating system makes Computer file, files and Directory (computing), directories on a Computer data storage, storage device (such as Hard disk drive, hard drive, CD-ROM, or network share) available f ...
* mount (Unix)
In computing, mount is a command in various operating systems. Before a user can access a file on a Unix-like machine, the file system on the device which contains the file needs to be mounted with the mount command. Frequently mount is used fo ...
* mtab
The mtab (mounted file systems table) file is a system information file, commonly found on Unix-like
A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although ...
References
External links
*
*
*
*
fstab man page
from Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
*
fstab (5)
- on
Ubuntu Manpage Repository
Kfstab
{{unix commands
Configuration files
Unix file system technology