FSTAB(5) FreeBSD File Formats Manual FSTAB(5)
NAME
fstab - static information about the file systems
SYNOPSIS
#include <fstab.h>
DESCRIPTION
The file fstab contains descriptive information about the various file
systems. fstab is only read by programs, and not written; it is the duty
of the system administrator to properly create and maintain this file.
Each file system is described on a separate line; fields on each line are
separated by tabs or spaces. The order of records in fstab is important
because fsck(8), mount(8), and umount(8) sequentially iterate through
fstab doing their thing.
The first field, (fs_spec), describes the special device or remote file
system to be mounted. The contents are decoded by the strunvis(3)
function. This allows using spaces or tabs in the device name which
would be interpreted as field separators otherwise.
The second field, (fs_file), describes the mount point for the file
system. For swap partitions, this field should be specified as "none".
The contents are decoded by the strunvis(3) function, as above.
The third field, (fs_vfstype), describes the type of the file system.
The system can support various file system types. Only the root, /usr,
and /tmp file systems need be statically compiled into the kernel;
everything else will be automatically loaded at mount time. (Exception:
the FFS cannot currently be demand-loaded.) Some people still prefer to
statically compile other file systems as well.
The fourth field, (fs_mntops), describes the mount options associated
with the file system. It is formatted as a comma separated list of
options. It contains at least the type of mount (see fs_type below) plus
any additional options appropriate to the file system type. See the
options flag (-o) in the mount(8) page and the file system specific page,
such as mount_nfs(8), for additional options that may be specified. All
options that can be given to the file system specific mount commands can
be used in fstab as well. They just need to be formatted a bit
differently. The arguments of the -o option can be used without the
preceding -o flag. Other options need both the file system specific flag
and its argument, separated by an equal sign. For example, mounting an
msdosfs(5) filesystem, the options
-o sync -o noatime -m 644 -M 755 -u foo -g bar
should be written as
sync,noatime,-m=644,-M=755,-u=foo,-g=bar
in the option field of fstab.
If the options "userquota" and/or "groupquota" are specified, the file
system is automatically processed by the quotacheck(8) command, and user
and/or group disk quotas are enabled with quotaon(8). By default, file
system quotas are maintained in files named quota.user and quota.group
which are located at the root of the associated file system. These
defaults may be overridden by putting an equal sign and an alternative
absolute pathname following the quota option. Thus, if the user quota
file for /tmp is stored in /var/quotas/tmp.user, this location can be
specified as:
userquota=/var/quotas/tmp.user
If the option "failok" is specified, the system will ignore any error
which happens during the mount of that filesystem, which would otherwise
cause the system to drop into single user mode. This option is
implemented by the mount(8) command and will not be passed to the kernel.
If the option "noauto" is specified, the file system will not be
automatically mounted at system startup. Note that, for network file
systems of third party types (i.e., types supported by additional
software not included in the base system) to be automatically mounted at
system startup, the extra_netfs_types rc.conf(5) variable must be used to
extend the rc(8) startup script's list of network file system types.
If the option "late" is specified, the file system will be automatically
mounted at a stage of system startup after remote mount points are
mounted. For more detail about this option, see the mount(8) manual
page.
If the option "update" is specified, it indicates that the status of an
already mounted file system should be changed accordingly. This allows,
for example, file systems mounted read-only to be upgraded read-write and
vice-versa. By default, an entry corresponding to a file systems that is
already mounted is going to be skipped over when processing fstab, unless
it's a root file system, in which case logic similar to "update" is
applied automatically.
The "update" option is typically used in conjunction with two fstab
files. The first fstab file is used to set up the initial set of file
systems. The second fstab file is then run to update the initial set of
file systems and to add additional file systems.
The type of the mount is extracted from the fs_mntops field and stored
separately in the fs_type field (it is not deleted from the fs_mntops
field). If fs_type is "rw" or "ro" then the file system whose name is
given in the fs_file field is normally mounted read-write or read-only on
the specified special file.
If fs_type is "sw" then the special file is made available as a piece of
swap space by the swapon(8) command at the end of the system reboot
procedure. For swap devices, the keyword "trimonce" triggers the
delivery of a BIO_DELETE command to the device. This command marks the
device's blocks as unused, except those that might store a disk label.
This marking can erase a crash dump. To delay swapon for a device until
after savecore has copied the crash dump to another location, use the
"late" option. For vnode-backed swap spaces, "file" is supported in the
fs_mntops field. When fs_spec is an md(4) device file ("md" or
"md[0-9]*") and "file" is specified in fs_mntopts, an md(4) device is
created with the specified file used as backing store, and then the new
device is used as swap space. Swap entries on .eli devices will cause
automatic creation of encrypted devices. The "ealgo", "aalgo", "keylen",
"notrim", and "sectorsize" options may be passed to control those geli(8)
parameters. The fields other than fs_spec and fs_type are unused. If
fs_type is specified as "xx" the entry is ignored. This is useful to
show disk partitions which are currently unused.
The fifth field, (fs_freq), is used for these file systems by the dump(8)
command to determine which file systems need to be dumped. If the fifth
field is not present, a value of zero is returned and dump will assume
that the file system does not need to be dumped. If the fifth field is
greater than 0, then it specifies the number of days between dumps for
this file system.
The sixth field, (fs_passno), is used by the fsck(8) and quotacheck(8)
programs to determine the order in which file system and quota checks are
done at reboot time. The fs_passno field can be any value between 0 and
`INT_MAX-1'.
The root file system should be specified with a fs_passno of 1, and other
file systems should have a fs_passno of 2 or greater. A file system with
a fs_passno value of 1 is always checked sequentially and be completed
before another file system is processed, and it will be processed before
all file systems with a larger fs_passno.
For any given value of fs_passno, file systems within a drive will be
checked sequentially, but file systems on different drives will be
checked at the same time to utilize parallelism available in the
hardware. Once all file system checks are complete for the current
fs_passno, the same process will start over for the next fs_passno.
If the sixth field is not present or is zero, a value of zero is returned
and fsck(8) and quotacheck(8) will assume that the file system does not
need to be checked.
The fs_passno field can be used to implement finer control when the
system utilities may determine that the file system resides on a
different physical device, when it actually does not, as with a ccd(4)
device. All file systems with a lower fs_passno value will be completed
before starting on file systems with a higher fs_passno value. E.g. all
file systems with a fs_passno of 2 will be completed before any file
systems with a fs_passno of 3 or greater are started. Gaps are allowed
between the different fs_passno values. E.g. file systems listed in
/etc/fstab may have fs_passno values such as 0, 1, 2, 15, 100, 200, 300,
and may appear in any order within /etc/fstab.
#define FSTAB_RW "rw" /* read/write device */
#define FSTAB_RQ "rq" /* read/write with quotas */
#define FSTAB_RO "ro" /* read-only device */
#define FSTAB_SW "sw" /* swap device */
#define FSTAB_XX "xx" /* ignore totally */
struct fstab {
char *fs_spec; /* block special device name */
char *fs_file; /* file system path prefix */
char *fs_vfstype; /* File system type, ufs, nfs */
char *fs_mntops; /* Mount options ala -o */
char *fs_type; /* FSTAB_* from fs_mntops */
int fs_freq; /* dump frequency, in days */
int fs_passno; /* pass number on parallel fsck */
};
The proper way to read records from fstab is to use the routines
getfsent(3), getfsspec(3), getfstype(3), and getfsfile(3).
FILES
/etc/fstab The file fstab resides in /etc.
EXAMPLES
# Device Mountpoint FStype Options Dump Pass#
#
# UFS file system.
/dev/da0p2 / ufs rw 1 1
#
# Swap space on a block device.
/dev/da0p1 none swap sw 0 0
#
# Swap space using a block device with GBDE/GELI encyption.
# aalgo, ealgo, keylen, sectorsize options are available
# for .eli devices.
/dev/da1p1.bde none swap sw 0 0
/dev/da1p2.eli none swap sw 0 0
#
# tmpfs.
tmpfs /tmp tmpfs rw,size=1g,mode=1777 0 0
#
# UFS file system on a swap-backed md(4). /dev/md10 is
# automatically created. If it is "md", a unit number
# will be automatically selected.
md10 /scratch mfs rw,-s1g 0 0
#
# Swap space on a vnode-backed md(4).
md11 none swap sw,file=/swapfile 0 0
#
# CDROM. "noauto" option is typically used because the
# media is removable.
/dev/cd0 /cdrom cd9660 ro,noauto 0 0
#
# NFS-exported file system. "serv" is an NFS server name
# or IP address.
serv:/export /nfs nfs rw,noinet6 0 0
SEE ALSO
getfsent(3), getvfsbyname(3), strunvis(3), ccd(4), dump(8), fsck(8),
geli(8), mount(8), quotacheck(8), quotaon(8), swapon(8), umount(8)
HISTORY
The fstab file format appeared in 4.0BSD.
FreeBSD 13.1-RELEASE-p6 April 14, 2014 FreeBSD 13.1-RELEASE-p6
man2web Home...