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FSTAB(5)                      File Formats Manual                     FSTAB(5)

     fstab - file system table for devices, types, and mount points

     #include <fstab.h>

     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.  Lines beginning with "#" are comments.  The
     order of records in fstab is important because fsck(8), mount(8), and
     umount(8) sequentially iterate through fstab doing their respective

     Each configuration line/record in fstab has the format:
           fs_spec fs_file fs_vfstype fs_mntops fs_freq fs_passno

     The first field, (fs_spec), describes the block special device or remote
     file system to be mounted.  For file systems of type ffs, the special
     file name is the block special file name, and not the character special
     file name.  If a program needs the character special file name, the
     program must create it by appending a "r" after the last "/" in the
     special file name.  (Note that for some file systems, e.g., kernfs,
     procfs, and tmpfs, this field has no applicable use, and any string may
     be supplied as a placeholder.  It is present simply for consistency of
     argument number and order.)

     If the first field is of the form "NAME=<value>" then all the dk(4) wedge
     partitions are searched for one that has a wedge name equal to <value>
     and the device corresponding to it is selected.

     If the first field starts with the prefix "ROOT." the prefix is replaced
     with "/dev/[root_device]", where [root_device] is the value of the
     "kern.root_device" sysctl.

     The second field, (fs_file), describes the mount point for the file
     system.  For swap and dump partitions, this field should be specified as

     The third field, (fs_vfstype), describes the type of the file system.
     The system currently supports these file systems:

           adosfs    an AmigaDOS file system.

           cd9660    an ISO 9660 CD-ROM file system.

           ext2fs    an implementation of the Linux "Second Extended

           fdesc     an implementation of /dev/fd.

           ffs       a local UNIX file system.

           filecore  a file system for RISC OS.

           kernfs    various and sundry kernel statistics.

           lfs       a log-structured file-system.

           mfs       a local memory-based UNIX file system.

           msdos     an MS-DOS "FAT file system".

           nfs       a Sun Microsystems compatible "Network File System".

           ntfs      a file system used by Windows NT.  Still experimental.

           null      a loop-back file system, allowing parts of the system to
                     be viewed elsewhere.

           overlay   a demonstration of layered file systems.

           portal    a general file system interface, currently supports TCP
                     and FS mounts.

           procfs    a local file system of process information.

           ptyfs     a pseudo-terminal device file system.

           swap      a disk partition to be used for swapping and paging.

           tmpfs     an efficient memory file system.

           umap      a user and group re-mapping file system.

           union     a translucent file system.

           zfs       a ZFS file system.

     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.

     The option "auto" can be used in the "noauto" form to cause a file system
     not to be mounted automatically (with "mount -a" , or system boot time).

     If the options "userquota" and/or "groupquota" are specified, the file
     system is automatically processed by the quotacheck(8) command, and
     legacy 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:


     It is recommended to turn on the new, in-file system quota with tunefs(8)
     or at newfs(8) time, and to not use the "userquota" or "groupquota"
     options.  Migration of limits to the new in-file system quota can be
     handled via quotadump(8) and quotarestore(8).

     The option "rump" is used to mount the file system using a rump(3)
     userspace server instead of the kernel server.

     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" or "dp" then the special
     file is made available as a piece of swap or dump space by the swapctl(8)
     command towards the beginning of the system reboot procedure.  See
     swapctl(8) for more information on configuring swap and dump devices.
     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(8) will assume
     that the file system does not need to be dumped.

     The sixth field, (fs_passno), is used by the fsck(8) program to determine
     the order in which file system checks are done at reboot time.  The root
     file system should be specified with a fs_passno of 1, and other file
     systems should have a fs_passno of 2.  Filesystems within a drive will be
     checked sequentially, but file systems on different drives will be
     checked at the same time to use parallelism available in the hardware.
     If the sixth field is not present or zero, a value of zero is returned
     and fsck(8) will assume that the file system does not need to be checked.

     #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_DP        "dp"    /* dump 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;    /* type of file system */
             char    *fs_mntops;     /* comma separated mount options */
             char    *fs_type;       /* rw, ro, sw, or xx */
             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), and getfsfile(3).

     /etc/fstab  The location of fstab configuration file.

                 Some useful configuration examples.

     To use "NAME" on a non-GPT disk, use:

     NAME=sb2k5Root/a        /       ffs     rw,log           1 1
     NAME=sb2k5Root/b        none    swap    sw,dp            0 0

     For a gpt(8) disk, use:

     NAME=firstpartition     /       ffs     rw,log           1 1
     NAME=secondpartition    none    swap    sw,dp            0 0

     getfsent(3), getfsspecname(3), mount(8), swapctl(8)

     The fstab file format appeared in 4.0BSD.

NetBSD 9.99                     April 19, 2020                     NetBSD 9.99