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diff --git a/mount/mount.8 b/mount/mount.8 new file mode 100644 index 0000000..d64aa2b --- /dev/null +++ b/mount/mount.8 @@ -0,0 +1,2614 @@ +.\" Copyright (c) 1996-2004 Andries Brouwer +.\" +.\" This page is somewhat derived from a page that was +.\" (c) 1980, 1989, 1991 The Regents of the University of California +.\" and had been heavily modified by Rik Faith and myself. +.\" (Probably no BSD text remains.) +.\" Fragments of text were written by Werner Almesberger, Remy Card, +.\" Stephen Tweedie and Eric Youngdale. +.\" +.\" This is free documentation; you can redistribute it and/or +.\" modify it under the terms of the GNU General Public License as +.\" published by the Free Software Foundation; either version 2 of +.\" the License, or (at your option) any later version. +.\" +.\" The GNU General Public License's references to "object code" +.\" and "executables" are to be interpreted as the output of any +.\" document formatting or typesetting system, including +.\" intermediate and printed output. +.\" +.\" This manual is distributed in the hope that it will be useful, +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +.\" GNU General Public License for more details. +.\" +.\" You should have received a copy of the GNU General Public +.\" License along with this manual; if not, write to the Free +.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, +.\" USA. +.\" +.\" 960705, aeb: version for mount-2.7g +.\" 970114, aeb: xiafs and ext are dead; romfs is new +.\" 970623, aeb: -F option +.\" 970914, reg: -s option +.\" 981111, K.Garloff: /etc/filesystems +.\" 990111, aeb: documented /sbin/mount.smbfs +.\" 990730, Yann Droneaud <lch@multimania.com>: updated page +.\" 991214, Elrond <Elrond@Wunder-Nett.org>: added some docs on devpts +.\" 010714, Michael K. Johnson <johnsonm@redhat.com> added -O +.\" 010725, Nikita Danilov <NikitaDanilov@Yahoo.COM>: reiserfs options +.\" 011124, Karl Eichwalder <ke@gnu.franken.de>: tmpfs options +.\" +.TH MOUNT 8 "2004-12-16" "Linux 2.6" "Linux Programmer's Manual" +.SH NAME +mount \- mount a filesystem +.SH SYNOPSIS +.B mount +.RB [ \-lhV ] +.LP +.BI "mount \-a +.RB [ \-fFnrsvw ] +.RB [ \-t +.IR vfstype ] +.RB [ \-O +.IR optlist ] +.LP +.B mount +.RB [ \-fnrsvw ] +.RB [ \-o +.IR option [ \fB,\fPoption ]...] +.IR device | dir +.LP +.B mount +.RB [ \-fnrsvw ] +.RB [ \-t +.IB vfstype ] +.RB [ \-o +.IR options ] +.I device dir +.SH DESCRIPTION +All files accessible in a Unix system are arranged in one big +tree, the file hierarchy, rooted at +.BR / . +These files can be spread out over several devices. The +.B mount +command serves to attach the filesystem found on some device +to the big file tree. Conversely, the +.BR umount (8) +command will detach it again. + +The standard form of the +.B mount +command, is +.RS + +.br +.BI "mount \-t" " type device dir" +.br + +.RE +This tells the kernel to attach the filesystem found on +.I device +(which is of type +.IR type ) +at the directory +.IR dir . +The previous contents (if any) and owner and mode of +.I dir +become invisible, and as long as this filesystem remains mounted, +the pathname +.I dir +refers to the root of the filesystem on +.IR device . + +.B The listing and help. +.RS +Three forms of invocation do not actually mount anything: +.TP +.B "mount \-h" +prints a help message +.TP +.B "mount \-V" +prints a version string +.TP +.BR "mount " [ -l "] [" "-t \fItype\fP" ] +lists all mounted filesystems (of type +.IR type ). +The option \-l adds the labels in this listing. +See below. +.RE + +.B The bind mounts. +.RS +.\" In fact since 2.3.99. At first the syntax was mount -t bind. +Since Linux 2.4.0 it is possible to remount part of the +file hierarchy somewhere else. The call is +.RS +.br +.B mount --bind +.I olddir newdir +.RE +or shortoption +.RS +.br +.B mount -B +.I olddir newdir +.RE +or fstab entry is: +.RS +.br +.I /olddir +.I /newdir +.B none bind +.RE + +After this call the same contents is accessible in two places. +One can also remount a single file (on a single file). + +This call attaches only (part of) a single filesystem, not possible +submounts. The entire file hierarchy including submounts is attached +a second place using +.RS +.br +.B mount --rbind +.I olddir newdir +.RE +or shortoption +.RS +.br +.B mount -R +.I olddir newdir +.RE +.\" available since Linux 2.4.11. + +Note that the filesystem mount options will remain the same as those +on the original mount point, and cannot be changed by passing the -o +option along with --bind/--rbind. +.RE + +.B The move operation. +.RS +Since Linux 2.5.1 it is possible to atomically move a mounted tree +to another place. The call is +.RS +.br +.B mount --move +.I olddir newdir +.RE +or shortoption +.RS +.br +.B mount -M +.I olddir newdir +.RE +.RE + +.B The shared subtrees operations. +.RS +Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, +private, slave or unbindable. A shared mount provides ability to create mirrors +of that mount such that mounts and umounts within any of the mirrors propagate +to the other mirror. A slave mount receives propagation from its master, but +any not vice-versa. A private mount carries no propagation abilities. A +unbindable mount is a private mount which cannot cloned through a bind +operation. Detailed semantics is documented in Documentation/sharedsubtree.txt +file in the kernel source tree. + +.RS +.nf +.BI "mount --make-shared " mountpoint +.BI "mount --make-slave " mountpoint +.BI "mount --make-private " mountpoint +.BI "mount --make-unbindable " mountpoint +.fi +.RE + +The following commands allows one to recursively change the type of all the +mounts under a given mountpoint. + +.RS +.nf +.BI "mount --make-rshared " mountpoint +.BI "mount --make-rslave " mountpoint +.BI "mount --make-rprivate " mountpoint +.BI "mount --make-runbindable " mountpoint +.fi +.RE +.RE +.RE + +.B The device indication. +.RS +Most devices are indicated by a file name (of a block special device), like +.IR /dev/sda1 , +but there are other possibilities. For example, in the case of an NFS mount, +.I device +may look like +.IR knuth.cwi.nl:/dir . +It is possible to indicate a block special device using its +volume +.B LABEL +or +.B UUID +(see the \-L and \-U options below). + +.B The device indication. +.RS +Most devices are indicated by a file name (of a block special device), like +.IR /dev/sda1 , +but there are other possibilities. For example, in the case of an NFS mount, +.I device +may look like +.IR knuth.cwi.nl:/dir . +It is possible to indicate a block special device using its +volume +.B LABEL +or +.B UUID +(see the \-L and \-U options below). + +The +.I proc +filesystem is not associated with a special device, and when +mounting it, an arbitrary keyword, such as +.I proc +can be used instead of a device specification. +(The customary choice +.I none +is less fortunate: the error message `none busy' from +.B umount +can be confusing.) +.RE + +.B The /etc/fstab, /etc/mtab and /proc/mounts files. +.RS +The file +.I /etc/fstab +(see +.BR fstab (5)), +may contain lines describing what devices are usually +mounted where, using which options. +.LP +The command +.RS +.sp +.B mount \-a +.RB [ \-t +.IR type ] +.RB [ \-O +.IR optlist ] +.sp +.RE +(usually given in a bootscript) causes all filesystems mentioned in +.I fstab +(of the proper type and/or having or not having the proper options) +to be mounted as indicated, except for those whose line contains the +.B noauto +keyword. Adding the +.B \-F +option will make mount fork, so that the +filesystems are mounted simultaneously. +.LP +When mounting a filesystem mentioned in +.IR fstab +or +.IR mtab , +it suffices to give only the device, or only the mount point. + + +The programs +.B mount +and +.B umount +maintain a list of currently mounted filesystems in the file +.IR /etc/mtab . +If no arguments are given to +.BR mount , +this list is printed. + +When the +.I proc +filesystem is mounted (say at +.IR /proc ), +the files +.I /etc/mtab +and +.I /proc/mounts +have very similar contents. The former has somewhat +more information, such as the mount options used, +but is not necessarily up-to-date (cf. the +.B \-n +option below). It is possible to replace +.I /etc/mtab +by a symbolic link to +.IR /proc/mounts , +and especially when you have very large numbers of mounts +things will be much faster with that symlink, +but some information is lost that way, and in particular +working with the loop device will be less convenient, +and using the "user" option will fail. +.RE + +.B The non-superuser mounts. +.RS +Normally, only the superuser can mount filesystems. +However, when +.I fstab +contains the +.B user +option on a line, anybody can mount the corresponding system. +.LP +Thus, given a line +.RS +.sp +.B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide" +.sp +.RE +any user can mount the iso9660 filesystem found on his CDROM +using the command +.RS +.sp +.B "mount /dev/cdrom" +.sp +.RE +or +.RS +.sp +.B "mount /cd" +.sp +.RE +For more details, see +.BR fstab (5). +Only the user that mounted a filesystem can unmount it again. +If any user should be able to unmount, then use +.B users +instead of +.B user +in the +.I fstab +line. +The +.B owner +option is similar to the +.B user +option, with the restriction that the user must be the owner +of the special file. This may be useful e.g. for +.I /dev/fd +if a login script makes the console user owner of this device. +The +.B group +option is similar, with the restriction that the user must be +member of the group of the special file. +.RE + +.SH COMMAND LINE OPTIONS +The full set of mount options used by an invocation of +.B mount +is determined by first extracting the +mount options for the filesystem from the +.I fstab +table, then applying any options specified by the +.B \-o +argument, and finally applying a +.BR \-r " or " \-w +option, when present. + +Command line options available for the +.B mount +command: +.TP +.B \-V +Output version. +.TP +.B \-h +Print a help message. +.TP +.B \-v +Verbose mode. +.TP +.B \-a +Mount all filesystems (of the given types) mentioned in +.IR fstab . +.TP +.B \-F +(Used in conjunction with +.BR \-a .) +Fork off a new incarnation of mount for each device. +This will do the mounts on different devices or different NFS servers +in parallel. +This has the advantage that it is faster; also NFS timeouts go in +parallel. A disadvantage is that the mounts are done in undefined order. +Thus, you cannot use this option if you want to mount both +.I /usr +and +.IR /usr/spool . +.TP +.B \-f +Causes everything to be done except for the actual system call; if it's not +obvious, this ``fakes'' mounting the filesystem. This option is useful in +conjunction with the +.B \-v +flag to determine what the +.B mount +command is trying to do. It can also be used to add entries for devices +that were mounted earlier with the -n option. The -f option checks for +existing record in /etc/mtab and fails when the record already +exists (with regular non-fake mount, this check is done by kernel). +.TP +.B \-i +Don't call the /sbin/mount.<filesystem> helper even if it exists. +.TP +.B \-l +Add the labels in the mount output. Mount must have +permission to read the disk device (e.g. be suid root) for this to work. +One can set such a label for ext2, ext3 or ext4 using the +.BR e2label (8) +utility, or for XFS using +.BR xfs_admin (8), +or for reiserfs using +.BR reiserfstune (8). +.TP +.B \-n +Mount without writing in +.IR /etc/mtab . +This is necessary for example when +.I /etc +is on a read-only filesystem. +.TP +.BI \-p " num" +In case of a loop mount with encryption, read the passphrase from +file descriptor +.I num +instead of from the terminal. +.TP +.B \-s +Tolerate sloppy mount options rather than failing. This will ignore +mount options not supported by a filesystem type. Not all filesystems +support this option. This option exists for support of the Linux +autofs\-based automounter. +.TP +.B \-r +Mount the filesystem read-only. A synonym is +.BR "\-o ro" . + +Note that, depending on the filesystem type, state and kernel behavior, the +system may still write to the device. For example, Ext3 or ext4 will replay its +journal if the filesystem is dirty. To prevent this kind of write access, you +may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or +set the block device to read-only mode, see command +.BR blockdev (8). +.TP +.B \-w +Mount the filesystem read/write. This is the default. A synonym is +.BR "\-o rw" . +.TP +.BI \-L " label" +Mount the partition that has the specified +.IR label . +.TP +.BI \-U " uuid" +Mount the partition that has the specified +.IR uuid . +These two options require the file +.I /proc/partitions +(present since Linux 2.1.116) to exist. +.TP +.BI \-t " vfstype" +The argument following the +.B \-t +is used to indicate the filesystem type. The filesystem types which are +currently supported include: +.IR adfs , +.IR affs , +.IR autofs , +.IR cifs , +.IR coda , +.IR coherent , +.IR cramfs , +.IR debugfs , +.IR devpts , +.IR efs , +.IR ext , +.IR ext2 , +.IR ext3 , +.IR ext4 , +.IR hfs , +.IR hfsplus , +.IR hpfs , +.IR iso9660 , +.IR jfs , +.IR minix , +.IR msdos , +.IR ncpfs , +.IR nfs , +.IR nfs4 , +.IR ntfs , +.IR proc , +.IR qnx4 , +.IR ramfs , +.IR reiserfs , +.IR romfs , +.IR smbfs , +.IR sysv , +.IR tmpfs , +.IR udf , +.IR ufs , +.IR umsdos , +.IR usbfs , +.IR vfat , +.IR xenix , +.IR xfs , +.IR xiafs . +Note that coherent, sysv and xenix are equivalent and that +.I xenix +and +.I coherent +will be removed at some point in the future \(em use +.I sysv +instead. Since kernel version 2.1.21 the types +.I ext +and +.I xiafs +do not exist anymore. Earlier, +.I usbfs +was known as +.IR usbdevfs . +Note, the real list of all supported filesystems depends on your +kernel. + +For most types all the +.B mount +program has to do is issue a simple +.IR mount (2) +system call, and no detailed knowledge of the filesystem type is required. +For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) ad hoc code is +necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems +have a separate mount program. In order to make it possible to +treat all types in a uniform way, mount will execute the program +.BI /sbin/mount. TYPE +(if that exists) when called with type +.IR TYPE . +Since various versions of the +.B smbmount +program have different calling conventions, +.B /sbin/mount.smbfs +may have to be a shell script that sets up the desired call. + +If no +.B \-t +option is given, or if the +.B auto +type is specified, mount will try to guess the desired type. +Mount uses the blkid or volume_id library for guessing the filesystem +type; if that does not turn up anything that looks familiar, +mount will try to read the file +.IR /etc/filesystems , +or, if that does not exist, +.IR /proc/filesystems . +All of the filesystem types listed there will be tried, +except for those that are labeled "nodev" (e.g., +.IR devpts , +.I proc +and +.IR nfs ). +If +.I /etc/filesystems +ends in a line with a single * only, mount will read +.I /proc/filesystems +afterwards. + +The +.B auto +type may be useful for user-mounted floppies. +Creating a file +.I /etc/filesystems +can be useful to change the probe order (e.g., to try vfat before msdos +or ext3 before ext2) or if you use a kernel module autoloader. +Warning: the probing uses a heuristic (the presence of appropriate `magic'), +and could recognize the wrong filesystem type, possibly with catastrophic +consequences. If your data is valuable, don't ask +.B mount +to guess. + +More than one type may be specified in a comma separated +list. The list of filesystem types can be prefixed with +.B no +to specify the filesystem types on which no action should be taken. +(This can be meaningful with the +.B \-a +option.) + +For example, the command: +.RS +.RS +.B "mount \-a \-t nomsdos,ext" +.RE +mounts all filesystems except those of type +.I msdos +and +.IR ext . +.RE +.TP +.B \-O +Used in conjunction with +.BR \-a , +to limit the set of filesystems to which the +.B \-a +is applied. Like +.B \-t +in this regard except that it is useless except in the context of +.BR \-a . +For example, the command: +.RS +.RS +.sp +.B "mount \-a \-O no_netdev" +.sp +.RE +mounts all filesystems except those which have the option +.I _netdev +specified in the options field in the +.I /etc/fstab +file. + +It is different from +.B \-t +in that each option is matched exactly; a leading +.B no +at the beginning of one option does not negate the rest. + +The +.B \-t +and +.B \-O +options are cumulative in effect; that is, the command +.RS +.sp +.B "mount \-a \-t ext2 \-O _netdev" +.sp +.RE +mounts all ext2 filesystems with the _netdev option, not all filesystems +that are either ext2 or have the _netdev option specified. +.RE +.TP +.B \-o +Options are specified with a +.B \-o +flag followed by a comma separated string of options. For example: +.RS +.RS +.B "mount LABEL=mydisk \-o noatime,nouser" +.RE + +For more details, see +.B FILESYSTEM INDEPENDENT MOUNT OPTIONS +and +.B FILESYSTEM SPECIFIC MOUNT OPTIONS +sections. +.RE +.TP +.B \-B, \-\-bind +Remount a subtree somewhere else (so that its contents are available +in both places). See above. +.TP +.B \-R, \-\-rbind +Remount a subtree and all possible submounts somewhere else (so that its +contents are available in both places). See above. +.TP +.B \-M, \-\-move +Move a subtree to some other place. See above. +.RE + +.SH FILESYSTEM INDEPENDENT MOUNT OPTIONS +Some of these options are only useful when they appear in the +.I /etc/fstab +file. + +Some of these options could be enabled or disabled by default +in the system kernel. To check the current setting see the options +in /proc/mounts. + +The following options apply to any filesystem that is being +mounted (but not every filesystem actually honors them - e.g., the +.B sync +option today has effect only for ext2, ext3, fat, vfat and ufs): + +.TP +.B async +All I/O to the filesystem should be done asynchronously. (See also the +.B sync +option.) +.TP +.B atime +Update inode access time for each access. See also the +.B strictatime +mount option. +.TP +.B noatime +Do not update inode access times on this filesystem (e.g, for faster +access on the news spool to speed up news servers). +.TP +.B auto +Can be mounted with the +.B \-a +option. +.TP +.B noauto +Can only be mounted explicitly (i.e., the +.B \-a +option will not cause the filesystem to be mounted). +.TP +\fBcontext=\fP\fIcontext\fP, \fBfscontext=\fP\fIcontext\fP, \fBdefcontext=\fP\fIcontext\fP and \fBrootcontext=\fP\fIcontext\fP +The +.BR context= +option is useful when mounting filesystems that do not support +extended attributes, such as a floppy or hard disk formatted with VFAT, or +systems that are not normally running under SELinux, such as an ext3 formatted +disk from a non-SELinux workstation. You can also use +.BR context= +on filesystems you do not trust, such as a floppy. It also helps in compatibility with +xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where +xattrs are supported, you can save time not having to label every file by +assigning the entire disk one security context. + +A commonly used option for removable media is +.BR context=system_u:object_r:removable_t . + +Two other options are +.BR fscontext= +and +.BR defcontext= , +both of which are mutually exclusive of the context option. This means you +can use fscontext and defcontext with each other, but neither can be used with +context. + +The +.BR fscontext= +option works for all filesystems, regardless of their xattr +support. The fscontext option sets the overarching filesystem label to a +specific security context. This filesystem label is separate from the +individual labels on the files. It represents the entire filesystem for +certain kinds of permission checks, such as during mount or file creation. +Individual file labels are still obtained from the xattrs on the files +themselves. The context option actually sets the aggregate context that +fscontext provides, in addition to supplying the same label for individual +files. + +You can set the default security context for unlabeled files using +.BR defcontext= +option. This overrides the value set for unlabeled files in the policy and requires a +filesystem that supports xattr labeling. + +The +.BR rootcontext= +option allows you to explicitly label the root inode of a FS being mounted +before that FS or inode because visable to userspace. This was found to be +useful for things like stateless linux. + +For more details, see +.BR selinux (8) + +.TP +.B defaults +Use default options: +.BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async. +.TP +.B dev +Interpret character or block special devices on the filesystem. +.TP +.B nodev +Do not interpret character or block special devices on the file +system. +.TP +.B diratime +Update directory inode access times on this filesystem. This is the default. +.TP +.B nodiratime +Do not update directory inode access times on this filesystem. +.TP +.B dirsync +All directory updates within the filesystem should be done synchronously. +This affects the following system calls: creat, link, unlink, symlink, +mkdir, rmdir, mknod and rename. +.TP +.B exec +Permit execution of binaries. +.TP +.B noexec +Do not allow direct execution of any binaries on the mounted filesystem. +(Until recently it was possible to run binaries anyway using a command like +/lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.) +.TP +.B group +Allow an ordinary (i.e., non-root) user to mount the filesystem if one +of his groups matches the group of the device. +This option implies the options +.BR nosuid " and " nodev +(unless overridden by subsequent options, as in the option line +.BR group,dev,suid ). +.TP +.B encryption +Specifies an encryption algorithm to use. Used in conjunction with the +.BR loop " option." +.TP +.B keybits +Specifies the key size to use for an encryption algorithm. Used in conjunction +with the +.BR loop " and " encryption " options." +.B nofail +Do not report errors for this device if it does not exist. +.B iversion +Every time the inode is modified, the i_version field will be incremented. +.TP +.B noiversion +Do not increment the i_version inode field. +.TP +.B mand +Allow mandatory locks on this filesystem. See +.BR fcntl (2). +.TP +.B nomand +Do not allow mandatory locks on this filesystem. +.TP +.B _netdev +The filesystem resides on a device that requires network access +(used to prevent the system from attempting to mount these filesystems +until the network has been enabled on the system). +.TP +.B nofail +Do not report errors for this device if it does not exist. +.TP +.B relatime +Update inode access times relative to modify or change time. Access +time is only updated if the previous access time was earlier than the +current modify or change time. (Similar to noatime, but doesn't break +mutt or other applications that need to know if a file has been read +since the last time it was modified.) +.TP +.B norelatime +Do not use +.B relatime +feature. See also the +.B strictatime +mount option. +.TP +.B strictatime +Allows to explicitly requesting full atime updates. This makes it +possible for kernel to defaults to +.B relatime +or +.B noatime +but still allow userspace to override it. For more details about the default +system mount options see /proc/mounts. +.TP +.B nostrictatime +Use the kernel's default behaviour for inode access time updates. +.TP +.B suid +Allow set-user-identifier or set-group-identifier bits to take +effect. +.TP +.B nosuid +Do not allow set-user-identifier or set-group-identifier bits to take +effect. (This seems safe, but is in fact rather unsafe if you have +suidperl(1) installed.) +.TP +.B owner +Allow an ordinary (i.e., non-root) user to mount the filesystem if he +is the owner of the device. +This option implies the options +.BR nosuid " and " nodev +(unless overridden by subsequent options, as in the option line +.BR owner,dev,suid ). +.TP +.B remount +Attempt to remount an already-mounted filesystem. This is commonly +used to change the mount flags for a filesystem, especially to make a +readonly filesystem writeable. It does not change device or mount point. + +The remount functionality follows the standard way how the mount command works +with options from fstab. It means the mount command doesn't read fstab (or +mtab) only when a +.IR device +and +.IR dir +are fully specified. + +.BR "mount -o remount,rw /dev/foo /dir" + +After this call all old mount options are replaced and arbitrary stuff from +fstab is ignored, except the loop= option which is internally generated and +maintained by the mount command. + +.BR "mount -o remount,rw /dir" + +After this call mount reads fstab (or mtab) and merges these options with +options from command line ( +.B -o +). +.TP +.B ro +Mount the filesystem read-only. +.TP +.B rw +Mount the filesystem read-write. +.TP +.B sync +All I/O to the filesystem should be done synchronously. In case of media with limited number of write cycles +(e.g. some flash drives) "sync" may cause life-cycle shortening. +.TP +.B user +Allow an ordinary user to mount the filesystem. +The name of the mounting user is written to mtab so that he can unmount +the filesystem again. +This option implies the options +.BR noexec ", " nosuid ", and " nodev +(unless overridden by subsequent options, as in the option line +.BR user,exec,dev,suid ). +.TP +.B nouser +Forbid an ordinary (i.e., non-root) user to mount the filesystem. +This is the default. +.TP +.B users +Allow every user to mount and unmount the filesystem. +This option implies the options +.BR noexec ", " nosuid ", and " nodev +(unless overridden by subsequent options, as in the option line +.BR users,exec,dev,suid ). + +.SH "FILESYSTEM SPECIFIC MOUNT OPTIONS" +The following options apply only to certain filesystems. +We sort them by filesystem. They all follow the +.B \-o +flag. + +What options are supported depends a bit on the running kernel. +More info may be found in the kernel source subdirectory +.IR Documentation/filesystems . + +.SH "Mount options for adfs" +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +Set the owner and group of the files in the filesystem (default: uid=gid=0). +.TP +\fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP +Set the permission mask for ADFS 'owner' permissions and 'other' permissions, +respectively (default: 0700 and 0077, respectively). +See also +.IR /usr/src/linux/Documentation/filesystems/adfs.txt . +.SH "Mount options for affs" +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +Set the owner and group of the root of the filesystem (default: uid=gid=0, +but with option +.B uid +or +.B gid +without specified value, the uid and gid of the current process are taken). +.TP +\fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP +Set the owner and group of all files. +.TP +.BI mode= value +Set the mode of all files to +.IR value " & 0777" +disregarding the original permissions. +Add search permission to directories that have read permission. +The value is given in octal. +.TP +.B protect +Do not allow any changes to the protection bits on the filesystem. +.TP +.B usemp +Set uid and gid of the root of the filesystem to the uid and gid +of the mount point upon the first sync or umount, and then +clear this option. Strange... +.TP +.B verbose +Print an informational message for each successful mount. +.TP +.BI prefix= string +Prefix used before volume name, when following a link. +.TP +.BI volume= string +Prefix (of length at most 30) used before '/' when following a symbolic link. +.TP +.BI reserved= value +(Default: 2.) Number of unused blocks at the start of the device. +.TP +.BI root= value +Give explicitly the location of the root block. +.TP +.BI bs= value +Give blocksize. Allowed values are 512, 1024, 2048, 4096. +.TP +.BR grpquota | noquota | quota | usrquota +These options are accepted but ignored. +(However, quota utilities may react to such strings in +.IR /etc/fstab .) + +.SH "Mount options for cifs" +See the options section of the +.BR mount.cifs (8) +man page (smbfs package must be installed). + +.SH "Mount options for coherent" +None. + +.SH "Mount options for debugfs" +The debugfs filesystem is a pseudo filesystem, traditionally mounted on +.IR /sys/kernel/debug . +.\" or just /debug +.\" present since 2.6.11 +There are no mount options. + +.SH "Mount options for devpts" +The devpts filesystem is a pseudo filesystem, traditionally mounted on +.IR /dev/pts . +In order to acquire a pseudo terminal, a process opens +.IR /dev/ptmx ; +the number of the pseudo terminal is then made available to the process +and the pseudo terminal slave can be accessed as +.IR /dev/pts/ <number>. +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +This sets the owner or the group of newly created PTYs to +the specified values. When nothing is specified, they will +be set to the UID and GID of the creating process. +For example, if there is a tty group with GID 5, then +.B gid=5 +will cause newly created PTYs to belong to the tty group. +.TP +.BI mode= value +Set the mode of newly created PTYs to the specified value. +The default is 0600. +A value of +.B mode=620 +and +.B gid=5 +makes "mesg y" the default on newly created PTYs. +.TP +\fBnewinstance +Create a private instance of devpts filesystem, such that +indices of ptys allocated in this new instance are +independent of indices created in other instances of devpts. + +All mounts of devpts without this +.B newinstance +option share the same set of pty indices (i.e legacy mode). +Each mount of devpts with the +.B newinstance +option has a private set of pty indices. + +This option is mainly used to support containers in the +linux kernel. It is implemented in linux kernel versions +starting with 2.6.29. Further, this mount option is valid +only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the +kernel configuration. + +To use this option effectively, +.IR /dev/ptmx +must be a symbolic link to +.IR pts/ptmx. +See +.IR Documentation/filesystems/devpts.txt +in the linux kernel source tree for details. +.TP +.BI ptmxmode= value + +Set the mode for the new +.IR ptmx +device node in the devpts filesystem. + +With the support for multiple instances of devpts (see +.B newinstance +option above), each instance has a private +.IR ptmx +node in the root of the devpts filesystem (typically +.IR /dev/pts/ptmx). + +For compatibility with older versions of the kernel, the +default mode of the new +.IR ptmx +node is 0000. +.BI ptmxmode= value +specifies a more useful mode for the +.IR ptmx +node and is highly recommended when the +.B newinstance +option is specified. + +This option is only implemented in linux kernel versions +starting with 2.6.29. Further this option is valid only if +CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel +configuration. + +.SH "Mount options for ext" +None. +Note that the `ext' filesystem is obsolete. Don't use it. +Since Linux version 2.1.21 extfs is no longer part of the kernel source. + +.SH "Mount options for ext2" +The `ext2' filesystem is the standard Linux filesystem. +.\" Due to a kernel bug, it may be mounted with random mount options +.\" (fixed in Linux 2.0.4). +Since Linux 2.5.46, for most mount options the default +is determined by the filesystem superblock. Set them with +.BR tune2fs (8). +.TP +.BR acl | noacl +Support POSIX Access Control Lists (or not). +.\" requires CONFIG_EXT2_FS_POSIX_ACL +.TP +.BR bsddf | minixdf +Set the behaviour for the +.I statfs +system call. The +.B minixdf +behaviour is to return in the +.I f_blocks +field the total number of blocks of the filesystem, while the +.B bsddf +behaviour (which is the default) is to subtract the overhead blocks +used by the ext2 filesystem and not available for file storage. Thus +.nf + +% mount /k -o minixdf; df /k; umount /k +Filesystem 1024-blocks Used Available Capacity Mounted on +/dev/sda6 2630655 86954 2412169 3% /k +% mount /k -o bsddf; df /k; umount /k +Filesystem 1024-blocks Used Available Capacity Mounted on +/dev/sda6 2543714 13 2412169 0% /k + +.fi +(Note that this example shows that one can add command line options +to the options given in +.IR /etc/fstab .) + +.TP +.BR check= { none | nocheck } +No checking is done at mount time. This is the default. This is fast. +It is wise to invoke +.BR e2fsck (8) +every now and then, e.g. at boot time. +.TP +.B debug +Print debugging info upon each (re)mount. +.TP +.BR errors= { continue | remount-ro | panic } +Define the behaviour when an error is encountered. +(Either ignore errors and just mark the filesystem erroneous and continue, +or remount the filesystem read-only, or panic and halt the system.) +The default is set in the filesystem superblock, and can be +changed using +.BR tune2fs (8). +.TP +.BR grpid | bsdgroups " and " nogrpid | sysvgroups +These options define what group id a newly created file gets. +When +.BR grpid +is set, it takes the group id of the directory in which it is created; +otherwise (the default) it takes the fsgid of the current process, unless +the directory has the setgid bit set, in which case it takes the gid +from the parent directory, and also gets the setgid bit set +if it is a directory itself. +.TP +.BR grpquota | noquota | quota | usrquota +These options are accepted but ignored. +.TP +.BR nobh +Do not attach buffer_heads to file pagecache. (Since 2.5.49.) +.TP +.BR nouid32 +Disables 32-bit UIDs and GIDs. This is for interoperability with older +kernels which only store and expect 16-bit values. +.TP +.BR oldalloc " or " orlov +Use old allocator or Orlov allocator for new inodes. Orlov is default. +.TP +\fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP +The ext2 filesystem reserves a certain percentage of the available +space (by default 5%, see +.BR mke2fs (8) +and +.BR tune2fs (8)). +These options determine who can use the reserved blocks. +(Roughly: whoever has the specified uid, or belongs to the specified group.) +.TP +.BI sb= n +Instead of block 1, use block +.I n +as superblock. This could be useful when the filesystem has been damaged. +(Earlier, copies of the superblock would be made every 8192 blocks: in +block 1, 8193, 16385, ... (and one got thousands of copies on +a big filesystem). Since version 1.08, +.B mke2fs +has a \-s (sparse superblock) option to reduce the number of backup +superblocks, and since version 1.15 this is the default. Note +that this may mean that ext2 filesystems created by a recent +.B mke2fs +cannot be mounted r/w under Linux 2.0.*.) +The block number here uses 1k units. Thus, if you want to use logical +block 32768 on a filesystem with 4k blocks, use "sb=131072". +.TP +.BR user_xattr | nouser_xattr +Support "user." extended attributes (or not). +.\" requires CONFIG_EXT2_FS_XATTR + + +.SH "Mount options for ext3" +The ext3 filesystem is a version of the ext2 filesystem which has been +enhanced with journalling. It supports the same options as ext2 as +well as the following additions: +.\" .TP +.\" .BR abort +.\" Mount the filesystem in abort mode, as if a fatal error has occurred. +.TP +.BR journal=update +Update the ext3 filesystem's journal to the current format. +.TP +.BR journal=inum +When a journal already exists, this option is ignored. Otherwise, it +specifies the number of the inode which will represent the ext3 filesystem's +journal file; ext3 will create a new journal, overwriting the old contents +of the file whose inode number is +.IR inum . +.TP +.BR noload +Do not load the ext3 filesystem's journal on mounting. +.TP +.BR data= { journal | ordered | writeback } +Specifies the journalling mode for file data. Metadata is always journaled. +To use modes other than +.B ordered +on the root filesystem, pass the mode to the kernel as boot parameter, e.g. +.IR rootflags=data=journal . +.RS +.TP +.B journal +All data is committed into the journal prior to being written into the +main filesystem. +.TP +.B ordered +This is the default mode. All data is forced directly out to the main file +system prior to its metadata being committed to the journal. +.TP +.B writeback +Data ordering is not preserved - data may be written into the main +filesystem after its metadata has been committed to the journal. +This is rumoured to be the highest-throughput option. It guarantees +internal filesystem integrity, however it can allow old data to appear +in files after a crash and journal recovery. +.RE +.TP +.BR barrier=0 " / " barrier=1 " +This enables/disables barriers. barrier=0 disables it, barrier=1 enables it. +The ext3 filesystem does not enable write barriers by default. +.TP +.BI commit= nrsec +Sync all data and metadata every +.I nrsec +seconds. The default value is 5 seconds. Zero means default. +.TP +.BR user_xattr +Enable Extended User Attributes. See the +.BR attr (5) +manual page. +.TP +.BR acl +Enable POSIX Access Control Lists. See the +.BR acl (5) +manual page. + +.SH "Mount options for ext4" +The ext4 filesystem is an an advanced level of the ext3 filesystem which +incorporates scalability and reliability enhancements for supporting large +filesystem. + +The options +.B journal_dev, noload, data, commit, orlov, oldalloc, [no]user_xattr +.B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid +.B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota, usrquota +and +.B [no]bh +are backwardly compatible with ext3 or ext2. +.TP +.BR journal_checksum +Enable checksumming of the journal transactions. This will allow the recovery +code in e2fsck and the kernel to detect corruption in the kernel. It is a +compatible change and will be ignored by older kernels. +.TP +.BR journal_async_commit +Commit block can be written to disk without waiting for descriptor blocks. If +enabled older kernels cannot mount the device. This will enable +'journal_checksum' internally. +.TP +.BR journal=update +Update the ext4 filesystem's journal to the current format. +.TP +.BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier +This enables/disables the use of write barriers in the jbd code. barrier=0 +disables, barrier=1 enables. This also requires an IO stack which can support +barriers, and if jbd gets an error on a barrier write, it will disable again +with a warning. Write barriers enforce proper on-disk ordering of journal +commits, making volatile disk write caches safe to use, at some performance +penalty. If your disks are battery-backed in one way or another, disabling +barriers may safely improve performance. The mount options "barrier" and +"nobarrier" can also be used to enable or disable barriers, for consistency +with other ext4 mount options. + +The ext4 filesystem enables write barriers by default. +.TP +.BI inode_readahead= n +This tuning parameter controls the maximum number of inode table blocks that +ext4's inode table readahead algorithm will pre-read into the buffer cache. +The default value is 32 blocks. +.TP +.BI stripe= n +Number of filesystem blocks that mballoc will try to use for allocation size +and alignment. For RAID5/6 systems this should be the number of data disks * +RAID chunk size in filesystem blocks. +.TP +.BR delalloc +Deferring block allocation until write-out time. +.TP +.BR nodelalloc +Disable delayed allocation. Blocks are allocation when data is copied from user +to page cache. +.TP +.BI max_batch_time= usec +Maximum amount of time ext4 should wait for additional filesystem operations to +be batch together with a synchronous write operation. Since a synchronous +write operation is going to force a commit and then a wait for the I/O +complete, it doesn't cost much, and can be a huge throughput win, we wait for a +small amount of time to see if any other transactions can piggyback on the +synchronous write. The algorithm used is designed to automatically tune for +the speed of the disk, by measuring the amount of time (on average) that it +takes to finish committing a transaction. Call this time the "commit time". +If the time that the transactoin has been running is less than the commit time, +ext4 will try sleeping for the commit time to see if other operations will join +the transaction. The commit time is capped by the max_batch_time, which +defaults to 15000us (15ms). This optimization can be turned off entirely by +setting max_batch_time to 0. +.TP +.BI min_batch_time= usec +This parameter sets the commit time (as described above) to be at least +min_batch_time. It defaults to zero microseconds. Increasing this parameter +may improve the throughput of multi-threaded, synchronous workloads on very +fast disks, at the cost of increasing latency. +.TP +.BI journal_ioprio= prio +The I/O priority (from 0 to 7, where 0 is the highest priorty) which should be +used for I/O operations submitted by kjournald2 during a commit operation. +This defaults to 3, which is a slightly higher priority than the default I/O +priority. +.TP +.BR auto_da_alloc | noauto_da_alloc +Many broken applications don't use fsync() when noauto_da_alloc +replacing existing files via patterns such as + +fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo") + +or worse yet + +fd = open("foo", O_TRUNC)/write(fd,..)/close(fd). + +If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and +replace-via-truncate patterns and force that any delayed allocation blocks are +allocated such that at the next journal commit, in the default data=ordered +mode, the data blocks of the new file are forced to disk before the rename() +operation is commited. This provides roughly the same level of guarantees as +ext3, and avoids the "zero-length" problem that can happen when a system +crashes before the delayed allocation blocks are forced to disk. + +.SH "Mount options for fat" +(Note: +.I fat +is not a separate filesystem, but a common part of the +.IR msdos , +.I umsdos +and +.I vfat +filesystems.) +.TP +.BR blocksize= { 512 | 1024 | 2048 } +Set blocksize (default 512). This option is obsolete. +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +Set the owner and group of all files. +(Default: the uid and gid of the current process.) +.TP +.BI umask= value +Set the umask (the bitmask of the permissions that are +.B not +present). The default is the umask of the current process. +The value is given in octal. +.TP +.BI dmask= value +Set the umask applied to directories only. +The default is the umask of the current process. +The value is given in octal. +.\" Present since Linux 2.5.43. +.TP +.BI fmask= value +Set the umask applied to regular files only. +The default is the umask of the current process. +The value is given in octal. +.\" Present since Linux 2.5.43. +.TP +.BI allow_utime= value +This option controls the permission check of mtime/atime. +.RS +.TP +.B 20 +If current process is in group of file's group ID, you can change timestamp. +.TP +.B 2 +Other users can change timestamp. +.PP +The default is set from `dmask' option. (If the directory is writable, +.B utime(2) +is also allowed. I.e. ~dmask & 022) + +Normally +.B utime(2) +checks current process is owner of the file, or it has +CAP_FOWNER capability. But FAT filesystem doesn't have uid/gid on disk, so +normal check is too unflexible. With this option you can relax it. +.RE +.TP +.BI check= value +Three different levels of pickyness can be chosen: +.RS +.TP +.BR r [ elaxed ] +Upper and lower case are accepted and equivalent, long name parts are +truncated (e.g. +.I verylongname.foobar +becomes +.IR verylong.foo ), +leading and embedded spaces are accepted in each name part (name and extension). +.TP +.BR n [ ormal ] +Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are +rejected. This is the default. +.TP +.BR s [ trict ] +Like "normal", but names may not contain long parts and special characters +that are sometimes used on Linux, but are not accepted by MS-DOS are +rejected. (+, =, spaces, etc.) +.RE +.TP +.BI codepage= value +Sets the codepage for converting to shortname characters on FAT +and VFAT filesystems. By default, codepage 437 is used. +.TP +.BR conv= {b [ inary ]| t [ ext ]| a [ uto ]} +The +.I fat +filesystem can perform CRLF<-->NL (MS-DOS text format to UNIX text +format) conversion in the kernel. The following conversion modes are +available: +.RS +.TP +.B binary +no translation is performed. This is the default. +.TP +.B text +CRLF<-->NL translation is performed on all files. +.TP +.B auto +CRLF<-->NL translation is performed on all files that don't have a +"well-known binary" extension. The list of known extensions can be found at +the beginning of +.I fs/fat/misc.c +(as of 2.0, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj, +lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz, +gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi). +.PP +Programs that do computed lseeks won't like in-kernel text conversion. +Several people have had their data ruined by this translation. Beware! + +For filesystems mounted in binary mode, a conversion tool +(fromdos/todos) is available. This option is obsolete. +.RE +.TP +.BI cvf_format= module +Forces the driver to use the CVF (Compressed Volume File) module +.RI cvf_ module +instead of auto-detection. If the kernel supports kmod, the +cvf_format=xxx option also controls on-demand CVF module loading. +This option is obsolete. +.TP +.BI cvf_option= option +Option passed to the CVF module. This option is obsolete. +.TP +.B debug +Turn on the +.I debug +flag. A version string and a list of filesystem parameters will be +printed (these data are also printed if the parameters appear to be +inconsistent). +.TP +.BR fat= {12 | 16 | 32 } +Specify a 12, 16 or 32 bit fat. This overrides +the automatic FAT type detection routine. Use with caution! +.TP +.BI iocharset= value +Character set to use for converting between 8 bit characters +and 16 bit Unicode characters. The default is iso8859-1. +Long filenames are stored on disk in Unicode format. +.TP +.BI tz=UTC +This option disables the conversion of timestamps +between local time (as used by Windows on FAT) and UTC +(which Linux uses internally). This is particuluarly +useful when mounting devices (like digital cameras) +that are set to UTC in order to avoid the pitfalls of +local time. +.TP +.B quiet +Turn on the +.I quiet +flag. Attempts to chown or chmod files do not return errors, +although they fail. Use with caution! +.TP +.B showexec +If set, the execute permission bits of the file will be allowed only if +the extension part of the name is .EXE, .COM, or .BAT. Not set by default. +.TP +.B sys_immutable +If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. +Not set by default. +.TP +.B flush +If set, the filesystem will try to flush to disk more early than normal. +Not set by default. +.TP +.B usefree +Use the "free clusters" value stored on FSINFO. It'll +be used to determine number of free clusters without +scanning disk. But it's not used by default, because +recent Windows don't update it correctly in some +case. If you are sure the "free clusters" on FSINFO is +correct, by this option you can avoid scanning disk. +.TP +.BR dots ", " nodots ", " dotsOK= [ yes | no ] +Various misguided attempts to force Unix or DOS conventions +onto a FAT filesystem. + +.SH "Mount options for hfs" +.TP +.BI creator= cccc ", type=" cccc +Set the creator/type values as shown by the MacOS finder +used for creating new files. Default values: '????'. +.TP +.BI uid= n ", gid=" n +Set the owner and group of all files. +(Default: the uid and gid of the current process.) +.TP +.BI dir_umask= n ", file_umask=" n ", umask=" n +Set the umask used for all directories, all regular files, or all +files and directories. Defaults to the umask of the current process. +.TP +.BI session= n +Select the CDROM session to mount. +Defaults to leaving that decision to the CDROM driver. +This option will fail with anything but a CDROM as underlying device. +.TP +.BI part= n +Select partition number n from the device. +Only makes sense for CDROMS. +Defaults to not parsing the partition table at all. +.TP +.B quiet +Don't complain about invalid mount options. + +.SH "Mount options for hpfs" +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +Set the owner and group of all files. (Default: the uid and gid +of the current process.) +.TP +.BI umask= value +Set the umask (the bitmask of the permissions that are +.B not +present). The default is the umask of the current process. +The value is given in octal. +.TP +.BR case= { lower | asis } +Convert all files names to lower case, or leave them. +(Default: +.BR case=lower .) +.TP +.BR conv= { binary | text | auto } +For +.BR conv=text , +delete some random CRs (in particular, all followed by NL) +when reading a file. +For +.BR conv=auto , +choose more or less at random between +.BR conv=binary " and " conv=text . +For +.BR conv=binary , +just read what is in the file. This is the default. +.TP +.B nocheck +Do not abort mounting when certain consistency checks fail. + +.SH "Mount options for iso9660" +ISO 9660 is a standard describing a filesystem structure to be used +on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the +.I udf +filesystem.) + +Normal +.I iso9660 +filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename +length), and in addition all characters are in upper case. Also there is +no field for file ownership, protection, number of links, provision for +block/character devices, etc. + +Rock Ridge is an extension to iso9660 that provides all of these unix like +features. Basically there are extensions to each directory record that +supply all of the additional information, and when Rock Ridge is in use, +the filesystem is indistinguishable from a normal UNIX filesystem (except +that it is read-only, of course). +.TP +.B norock +Disable the use of Rock Ridge extensions, even if available. Cf.\& +.BR map . +.TP +.B nojoliet +Disable the use of Microsoft Joliet extensions, even if available. Cf.\& +.BR map . +.TP +.BR check= { r [ elaxed ]| s [ trict ]} +With +.BR check=relaxed , +a filename is first converted to lower case before doing the lookup. +This is probably only meaningful together with +.B norock +and +.BR map=normal . +(Default: +.BR check=strict .) +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +Give all files in the filesystem the indicated user or group id, +possibly overriding the information found in the Rock Ridge extensions. +(Default: +.BR uid=0,gid=0 .) +.TP +.BR map= { n [ ormal ]| o [ ff ]| a [ corn ]} +For non-Rock Ridge volumes, normal name translation maps upper +to lower case ASCII, drops a trailing `;1', and converts `;' to `.'. +With +.B map=off +no name translation is done. See +.BR norock . +(Default: +.BR map=normal .) +.B map=acorn +is like +.BR map=normal +but also apply Acorn extensions if present. +.TP +.BI mode= value +For non-Rock Ridge volumes, give all files the indicated mode. +(Default: read permission for everybody.) +Since Linux 2.1.37 one no longer needs to specify the mode in +decimal. (Octal is indicated by a leading 0.) +.TP +.B unhide +Also show hidden and associated files. +(If the ordinary files and the associated or hidden files have +the same filenames, this may make the ordinary files inaccessible.) +.TP +.BR block= { 512 | 1024 | 2048 } +Set the block size to the indicated value. +(Default: +.BR block=1024 .) +.TP +.BR conv= { a [ uto ]| b [ inary ]| m [ text ]| t [ ext ]} +(Default: +.BR conv=binary .) +Since Linux 1.3.54 this option has no effect anymore. +(And non-binary settings used to be very dangerous, +possibly leading to silent data corruption.) +.TP +.B cruft +If the high byte of the file length contains other garbage, +set this mount option to ignore the high order bits of the file length. +This implies that a file cannot be larger than 16MB. +.TP +.BI session= x +Select number of session on multisession CD. (Since 2.3.4.) +.TP +.BI sbsector= xxx +Session begins from sector xxx. (Since 2.3.4.) +.LP +The following options are the same as for vfat and specifying them only makes +sense when using discs encoded using Microsoft's Joliet extensions. +.TP +.BI iocharset= value +Character set to use for converting 16 bit Unicode characters on CD +to 8 bit characters. The default is iso8859-1. +.TP +.B utf8 +Convert 16 bit Unicode characters on CD to UTF-8. + +.SH "Mount options for jfs" +.TP +.BI iocharset= name +Character set to use for converting from Unicode to ASCII. The default is +to do no conversion. Use +.B iocharset=utf8 +for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in +the kernel +.I ".config" +file. +.TP +.BI resize= value +Resize the volume to +.I value +blocks. JFS only supports growing a volume, not shrinking it. This option +is only valid during a remount, when the volume is mounted read-write. The +.B resize +keyword with no value will grow the volume to the full size of the partition. +.TP +.B nointegrity +Do not write to the journal. The primary use of this option is to allow +for higher performance when restoring a volume from backup media. The +integrity of the volume is not guaranteed if the system abnormally abends. +.TP +.B integrity +Default. Commit metadata changes to the journal. Use this option to remount +a volume where the +.B nointegrity +option was previously specified in order to restore normal behavior. +.TP +.BR errors= { continue | remount-ro | panic } +Define the behaviour when an error is encountered. +(Either ignore errors and just mark the filesystem erroneous and continue, +or remount the filesystem read-only, or panic and halt the system.) +.TP +.BR noquota | quota | usrquota | grpquota +These options are accepted but ignored. + +.SH "Mount options for minix" +None. + +.SH "Mount options for msdos" +See mount options for fat. +If the +.I msdos +filesystem detects an inconsistency, it reports an error and sets the file +system read-only. The filesystem can be made writeable again by remounting +it. + +.SH "Mount options for ncpfs" +Just like +.IR nfs ", the " ncpfs +implementation expects a binary argument (a +.IR "struct ncp_mount_data" ) +to the mount system call. This argument is constructed by +.BR ncpmount (8) +and the current version of +.B mount +(2.12) does not know anything about ncpfs. + +.SH "Mount options for nfs and nfs4" +See the options section of the +.BR nfs (5) +man page (nfs-common package must be installed). + +The +.IR nfs " and " nfs4 +implementation expects a binary argument (a +.IR "struct nfs_mount_data" ) +to the mount system call. This argument is constructed by +.BR mount.nfs (8) +and the current version of +.B mount +(2.13) does not know anything about nfs and nfs4. + +.SH "Mount options for ntfs" +.TP +.BI iocharset= name +Character set to use when returning file names. +Unlike VFAT, NTFS suppresses names that contain +unconvertible characters. Deprecated. +.\" since 2.5.11 +.TP +.BI nls= name +New name for the option earlier called +.IR iocharset . +.\" since 2.5.11 +.TP +.BR utf8 +Use UTF-8 for converting file names. +.TP +.BR uni_xlate= { 0 | 1 | 2 } +For 0 (or `no' or `false'), do not use escape sequences +for unknown Unicode characters. +For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences +starting with ":". Here 2 give a little-endian encoding +and 1 a byteswapped bigendian encoding. +.TP +.B posix=[0|1] +If enabled (posix=1), the filesystem distinguishes between +upper and lower case. The 8.3 alias names are presented as +hard links instead of being suppressed. This option is obsolete. +.TP +\fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP +Set the file permission on the filesystem. +The umask value is given in octal. +By default, the files are owned by root and not readable by somebody else. + +.SH "Mount options for proc" +.TP +\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP +These options are recognized, but have no effect as far as I can see. + +.SH "Mount options for ramfs" +Ramfs is a memory based filesystem. Mount it and you have it. Unmount it +and it is gone. Present since Linux 2.3.99pre4. +There are no mount options. + +.SH "Mount options for reiserfs" +Reiserfs is a journaling filesystem. +.TP +.BR conv +Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, +using the 3.6 format for newly created objects. This filesystem will no +longer be compatible with reiserfs 3.5 tools. +.TP +.BR hash= { rupasov | tea | r5 | detect } +Choose which hash function reiserfs will use to find files within directories. +.RS +.TP +.B rupasov +A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, +mapping lexicographically close file names to close hash values. +This option should not be used, as it causes a high probability of hash +collisions. +.TP +.B tea +A Davis-Meyer function implemented by Jeremy Fitzhardinge. +It uses hash permuting bits in the name. It gets high randomness +and, therefore, low probability of hash collisions at some CPU cost. +This may be used if EHASHCOLLISION errors are experienced with the r5 hash. +.TP +.B r5 +A modified version of the rupasov hash. It is used by default and is +the best choice unless the filesystem has huge directories and +unusual file-name patterns. +.TP +.B detect +Instructs +.IR mount +to detect which hash function is in use by examining +the filesystem being mounted, and to write this information into +the reiserfs superblock. This is only useful on the first mount of +an old format filesystem. +.RE +.TP +.BR hashed_relocation +Tunes the block allocator. This may provide performance improvements +in some situations. +.TP +.BR no_unhashed_relocation +Tunes the block allocator. This may provide performance improvements +in some situations. +.TP +.BR noborder +Disable the border allocator algorithm invented by Yury Yu. Rupasov. +This may provide performance improvements in some situations. +.TP +.BR nolog +Disable journalling. This will provide slight performance improvements in +some situations at the cost of losing reiserfs's fast recovery from crashes. +Even with this option turned on, reiserfs still performs all journalling +operations, save for actual writes into its journalling area. Implementation +of +.IR nolog +is a work in progress. +.TP +.BR notail +By default, reiserfs stores small files and `file tails' directly into its +tree. This confuses some utilities such as +.BR LILO (8). +This option is used to disable packing of files into the tree. +.TP +.BR replayonly +Replay the transactions which are in the journal, but do not actually +mount the filesystem. Mainly used by +.IR reiserfsck . +.TP +.BI resize= number +A remount option which permits online expansion of reiserfs partitions. +Instructs reiserfs to assume that the device has +.I number +blocks. +This option is designed for use with devices which are under logical +volume management (LVM). +There is a special +.I resizer +utility which can be obtained from +.IR ftp://ftp.namesys.com/pub/reiserfsprogs . +.TP +.BR user_xattr +Enable Extended User Attributes. See the +.BR attr (5) +manual page. +.TP +.BR acl +Enable POSIX Access Control Lists. See the +.BR acl (5) +manual page. + +.SH "Mount options for romfs" +None. + +.SH "Mount options for smbfs" +Just like +.IR nfs ", the " smbfs +implementation expects a binary argument (a +.IR "struct smb_mount_data" ) +to the mount system call. This argument is constructed by +.BR smbmount (8) +and the current version of +.B mount +(2.12) does not know anything about smbfs. + +.SH "Mount options for sysv" +None. + +.SH "Mount options for tmpfs" +.TP +.BI size= nbytes +Override default maximum size of the filesystem. +The size is given in bytes, and rounded up to entire pages. +The default is half of the memory. The size parameter also accepts a suffix % +to limit this tmpfs instance to that percentage of your physical RAM: +the default, when neither size nor nr_blocks is specified, is size=50% +.TP +.B nr_blocks= +The same as size, but in blocks of PAGE_CACHE_SIZE +.TP +.B nr_inodes= +The maximum number of inodes for this instance. The default +is half of the number of your physical RAM pages, or (on a +machine with highmem) the number of lowmem RAM pages, +whichever is the lower. +.PP +The tmpfs mount options for sizing ( +.BR size , +.BR nr_blocks , +and +.BR nr_inodes ) +accept a suffix +.BR k , +.B m +or +.B g +for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount. + +.TP +.B mode= +Set initial permissions of the root directory. +.TP +.B uid= +The user id. +.TP +.B gid= +The group id. +.TP +.B mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList] +Set the NUMA memory allocation policy for all files in that +instance (if the kernel CONFIG_NUMA is enabled) - which can be adjusted on the +fly via 'mount -o remount ...' +.RS +.TP +.B default +prefers to allocate memory from the local node +.TP +.B prefer:Node +prefers to allocate memory from the given Node +.TP +.B bind:NodeList +allocates memory only from nodes in NodeList +.TP +.B interleave +prefers to allocate from each node in turn +.TP +.B interleave:NodeList +allocates from each node of NodeList in turn. +.PP +The NodeList format is a comma-separated list of decimal numbers and ranges, a +range being two hyphen-separated decimal numbers, the smallest and largest node +numbers in the range. For example, mpol=bind:0-3,5,7,9-15 + +Note that trying to mount a tmpfs with an mpol option will fail if the +running kernel does not support NUMA; and will fail if its nodelist +specifies a node which is not online. If your system relies on that +tmpfs being mounted, but from time to time runs a kernel built without +NUMA capability (perhaps a safe recovery kernel), or with fewer nodes +online, then it is advisable to omit the mpol option from automatic +mount options. It can be added later, when the tmpfs is already mounted +on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'. +.PE + +.SH "Mount options for udf" +udf is the "Universal Disk Format" filesystem defined by the Optical +Storage Technology Association, and is often used for DVD-ROM. +See also +.IR iso9660 . +.TP +.B gid= +Set the default group. +.TP +.B umask= +Set the default umask. +The value is given in octal. +.TP +.B uid= +Set the default user. +.TP +.B unhide +Show otherwise hidden files. +.TP +.B undelete +Show deleted files in lists. +.TP +.B nostrict +Unset strict conformance. +.\" .TP +.\" .B utf8 +.\" (unused). +.TP +.B iocharset +Set the NLS character set. +.TP +.B bs= +Set the block size. (May not work unless 2048.) +.TP +.B novrs +Skip volume sequence recognition. +.TP +.B session= +Set the CDROM session counting from 0. Default: last session. +.TP +.B anchor= +Override standard anchor location. Default: 256. +.TP +.B volume= +Override the VolumeDesc location. (unused) +.TP +.B partition= +Override the PartitionDesc location. (unused) +.TP +.B lastblock= +Set the last block of the filesystem. +.TP +.B fileset= +Override the fileset block location. (unused) +.TP +.B rootdir= +Override the root directory location. (unused) + +.SH "Mount options for ufs" +.TP +.BI ufstype= value +UFS is a filesystem widely used in different operating systems. +The problem are differences among implementations. Features of some +implementations are undocumented, so its hard to recognize the +type of ufs automatically. +That's why the user must specify the type of ufs by mount option. +Possible values are: +.RS +.TP +.B old +Old format of ufs, this is the default, read only. +(Don't forget to give the \-r option.) +.TP +.B 44bsd +For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD). +.TP +.B sun +For filesystems created by SunOS or Solaris on Sparc. +.TP +.B sunx86 +For filesystems created by Solaris on x86. +.TP +.B hp +For filesystems created by HP-UX, read-only. +.TP +.B nextstep +For filesystems created by NeXTStep (on NeXT station) (currently read only). +.TP +.B nextstep-cd +For NextStep CDROMs (block_size == 2048), read-only. +.TP +.B openstep +For filesystems created by OpenStep (currently read only). +The same filesystem type is also used by Mac OS X. +.RE + +.TP +.BI onerror= value +Set behaviour on error: +.RS +.TP +.B panic +If an error is encountered, cause a kernel panic. +.TP +.RB [ lock | umount | repair ] +These mount options don't do anything at present; +when an error is encountered only a console message is printed. +.RE + +.SH "Mount options for umsdos" +See mount options for msdos. +The +.B dotsOK +option is explicitly killed by +.IR umsdos . + +.SH "Mount options for vfat" +First of all, the mount options for +.I fat +are recognized. +The +.B dotsOK +option is explicitly killed by +.IR vfat . +Furthermore, there are +.TP +.B uni_xlate +Translate unhandled Unicode characters to special escaped sequences. +This lets you backup and restore filenames that are created with any +Unicode characters. Without this option, a '?' is used when no +translation is possible. The escape character is ':' because it is +otherwise illegal on the vfat filesystem. The escape sequence +that gets used, where u is the unicode character, +is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). +.TP +.B posix +Allow two files with names that only differ in case. +.TP +.B nonumtail +First try to make a short name without sequence number, +before trying +.IR name~num.ext . +.TP +.B utf8 +UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the +console. It can be be enabled for the filesystem with this option or disabled +with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets +disabled. +.TP +.BR shortname= { lower | win95 | winnt | mixed } + +Defines the behaviour for creation and display of filenames which fit into +8.3 characters. If a long name for a file exists, it will always be +preferred display. There are four modes: +: +.RS +.TP +.I lower +Force the short name to lower case upon display; store a long name when +the short name is not all upper case. This mode is the default. +.TP +.I win95 +Force the short name to upper case upon display; store a long name when +the short name is not all upper case. +.TP +.I winnt +Display the shortname as is; store a long name when the short name is +not all lower case or all upper case. +.TP +.I mixed +Display the short name as is; store a long name when the short name is not +all upper case. +.RE + + +.SH "Mount options for usbfs" +.TP +\fBdevuid=\fP\fIuid\fP and \fBdevgid=\fP\fIgid\fP and \fBdevmode=\fP\fImode\fP +Set the owner and group and mode of the device files in the usbfs filesystem +(default: uid=gid=0, mode=0644). The mode is given in octal. +.TP +\fBbusuid=\fP\fIuid\fP and \fBbusgid=\fP\fIgid\fP and \fBbusmode=\fP\fImode\fP +Set the owner and group and mode of the bus directories in the usbfs +filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. +.TP +\fBlistuid=\fP\fIuid\fP and \fBlistgid=\fP\fIgid\fP and \fBlistmode=\fP\fImode\fP +Set the owner and group and mode of the file +.I devices +(default: uid=gid=0, mode=0444). The mode is given in octal. + +.SH "Mount options for xenix" +None. + +.SH "Mount options for xfs" +.TP +.BI allocsize= size +Sets the buffered I/O end-of-file preallocation size when +doing delayed allocation writeout (default size is 64KiB). +Valid values for this option are page size (typically 4KiB) +through to 1GiB, inclusive, in power-of-2 increments. +.TP +.BR attr2 | noattr2 +The options enable/disable (default is disabled for backward +compatibility on-disk) an "opportunistic" improvement to be +made in the way inline extended attributes are stored on-disk. +When the new form is used for the first time (by setting or +removing extended attributes) the on-disk superblock feature +bit field will be updated to reflect this format being in use. +.TP +.B barrier +Enables the use of block layer write barriers for writes into +the journal and unwritten extent conversion. This allows for +drive level write caching to be enabled, for devices that +support write barriers. +.TP +.B dmapi +Enable the DMAPI (Data Management API) event callouts. +Use with the +.B mtpt +option. +.TP +.BR grpid | bsdgroups " and " nogrpid | sysvgroups +These options define what group ID a newly created file gets. +When grpid is set, it takes the group ID of the directory in +which it is created; otherwise (the default) it takes the fsgid +of the current process, unless the directory has the setgid bit +set, in which case it takes the gid from the parent directory, +and also gets the setgid bit set if it is a directory itself. +.TP +.BI ihashsize= value +Sets the number of hash buckets available for hashing the +in-memory inodes of the specified mount point. If a value +of zero is used, the value selected by the default algorithm +will be displayed in +.IR /proc/mounts . +.TP +.BR ikeep | noikeep +When inode clusters are emptied of inodes, keep them around +on the disk (ikeep) - this is the traditional XFS behaviour +and is still the default for now. Using the noikeep option, +inode clusters are returned to the free space pool. +.TP +.B inode64 +Indicates that XFS is allowed to create inodes at any location +in the filesystem, including those which will result in inode +numbers occupying more than 32 bits of significance. This is +provided for backwards compatibility, but causes problems for +backup applications that cannot handle large inode numbers. +.TP +.BR largeio | nolargeio +If +.B nolargeio +is specified, the optimal I/O reported in +st_blksize by +.BR stat (2) +will be as small as possible to allow user +applications to avoid inefficient read/modify/write I/O. +If +.B largeio +is specified, a filesystem that has a +.B swidth +specified +will return the +.B swidth +value (in bytes) in st_blksize. If the +filesystem does not have a +.B swidth +specified but does specify +an +.B allocsize +then +.B allocsize +(in bytes) will be returned +instead. +If neither of these two options are specified, then filesystem +will behave as if +.B nolargeio +was specified. +.TP +.BI logbufs= value +Set the number of in-memory log buffers. Valid numbers range +from 2-8 inclusive. +The default value is 8 buffers for filesystems with a +blocksize of 64KiB, 4 buffers for filesystems with a blocksize +of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB +and 2 buffers for all other configurations. Increasing the +number of buffers may increase performance on some workloads +at the cost of the memory used for the additional log buffers +and their associated control structures. +.TP +.BI logbsize= value +Set the size of each in-memory log buffer. +Size may be specified in bytes, or in kilobytes with a "k" suffix. +Valid sizes for version 1 and version 2 logs are 16384 (16k) and +32768 (32k). Valid sizes for version 2 logs also include +65536 (64k), 131072 (128k) and 262144 (256k). +The default value for machines with more than 32MiB of memory +is 32768, machines with less memory use 16384 by default. +.TP +\fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP +Use an external log (metadata journal) and/or real-time device. +An XFS filesystem has up to three parts: a data section, a log section, +and a real-time section. +The real-time section is optional, and the log section can be separate +from the data section or contained within it. +Refer to +.BR xfs (5). +.TP +.BI mtpt= mountpoint +Use with the +.B dmapi +option. The value specified here will be +included in the DMAPI mount event, and should be the path of +the actual mountpoint that is used. +.TP +.B noalign +Data allocations will not be aligned at stripe unit boundaries. +.TP +.B noatime +Access timestamps are not updated when a file is read. +.TP +.B norecovery +The filesystem will be mounted without running log recovery. +If the filesystem was not cleanly unmounted, it is likely to +be inconsistent when mounted in +.B norecovery +mode. +Some files or directories may not be accessible because of this. +Filesystems mounted +.B norecovery +must be mounted read-only or the mount will fail. +.TP +.B nouuid +Don't check for double mounted filesystems using the filesystem uuid. +This is useful to mount LVM snapshot volumes. +.TP +.B osyncisosync +Make O_SYNC writes implement true O_SYNC. WITHOUT this option, +Linux XFS behaves as if an +.B osyncisdsync +option is used, +which will make writes to files opened with the O_SYNC flag set +behave as if the O_DSYNC flag had been used instead. +This can result in better performance without compromising +data safety. +However if this option is not in effect, timestamp updates from +O_SYNC writes can be lost if the system crashes. +If timestamp updates are critical, use the +.B osyncisosync +option. +.TP +.BR uquota | usrquota | uqnoenforce | quota +User disk quota accounting enabled, and limits (optionally) +enforced. Refer to +.BR xfs_quota (8) +for further details. +.TP +.BR gquota | grpquota | gqnoenforce +Group disk quota accounting enabled and limits (optionally) +enforced. Refer to +.BR xfs_quota (8) +for further details. +.TP +.BR pquota | prjquota | pqnoenforce +Project disk quota accounting enabled and limits (optionally) +enforced. Refer to +.BR xfs_quota (8) +for further details. +.TP +\fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP +Used to specify the stripe unit and width for a RAID device or a stripe +volume. +.I value +must be specified in 512-byte block units. +If this option is not specified and the filesystem was made on a stripe +volume or the stripe width or unit were specified for the RAID device at +mkfs time, then the mount system call will restore the value from the +superblock. +For filesystems that are made directly on RAID devices, these options can be +used to override the information in the superblock if the underlying disk +layout changes after the filesystem has been created. +The +.B swidth +option is required if the +.B sunit +option has been specified, +and must be a multiple of the +.B sunit +value. +.TP +.B swalloc +Data allocations will be rounded up to stripe width boundaries +when the current end of file is being extended and the file +size is larger than the stripe width size. + +.SH "Mount options for xiafs" +None. Although nothing is wrong with xiafs, it is not used much, +and is not maintained. Probably one shouldn't use it. +Since Linux version 2.1.21 xiafs is no longer part of the kernel source. + +.SH "THE LOOP DEVICE" +One further possible type is a mount via the loop device. For example, +the command + +.nf +.B " mount /tmp/fdimage /mnt -t vfat -o loop=/dev/loop3 +.fi + +will set up the loop device +.I /dev/loop3 +to correspond to the file +.IR /tmp/fdimage , +and then mount this device on +.IR /mnt . + +This type of mount knows about four options, namely +.BR loop ", " offset ", " sizelimit " and " encryption , +that are really options to +.BR \%losetup (8). +If the mount requires a passphrase, you will be prompted for one unless +you specify a file descriptor to read from instead with the +.BR \-\-pass-fd +option. +(These options can be used in addition to those specific +to the filesystem type.) + +If no explicit loop device is mentioned +(but just an option `\fB\-o loop\fP' is given), then +.B mount +will try to find some unused loop device and use that. + +Since Linux 2.6.25 is supported auto-destruction of loop devices and +then any loop device allocated by +.B mount +will be freed by +.B umount +independently on +.IR /etc/mtab . + +You can also free a loop device by hand, using `losetup -d' or `umount -d`. + +.SH RETURN CODES +.B mount +has the following return codes (the bits can be ORed): +.TP +.BR 0 +success +.TP +.BR 1 +incorrect invocation or permissions +.TP +.BR 2 +system error (out of memory, cannot fork, no more loop devices) +.TP +.BR 4 +internal +.B mount +bug +.TP +.BR 8 +user interrupt +.TP +.BR 16 +problems writing or locking /etc/mtab +.TP +.BR 32 +mount failure +.TP +.BR 64 +some mount succeeded + +.SH NOTES +The syntax of external mount helpers is: + +.RS +.BI /sbin/mount. <suffix> +.I spec dir +.RB [ \-sfnv ] +.RB [ \-o +.IR options ] +.RE + +where the <suffix> is filesystem type and \-sfnvo options have same meaning like +standard mount options. + +.SH FILES +.TP 18n +.I /etc/fstab +filesystem table +.TP +.I /etc/mtab +table of mounted filesystems +.TP +.I /etc/mtab~ +lock file +.TP +.I /etc/mtab.tmp +temporary file +.TP +.I /etc/filesystems +a list of filesystem types to try + +.SH "SEE ALSO" +.BR mount (2), +.BR umount (2), +.BR fstab (5), +.BR umount (8), +.BR swapon (8), +.BR nfs (5), +.BR xfs (5), +.BR e2label (8), +.BR xfs_admin (8), +.BR mountd (8), +.BR nfsd (8), +.BR mke2fs (8), +.BR tune2fs (8), +.BR losetup (8) +.SH BUGS +It is possible for a corrupted filesystem to cause a crash. +.PP +Some Linux filesystems don't support +.B "\-o sync and \-o dirsync" +(the ext2, ext3, fat and vfat filesystems +.I do +support synchronous updates (a la BSD) when mounted with the +.B sync +option). +.PP +The +.B "\-o remount" +may not be able to change mount parameters (all +.IR ext2fs -specific +parameters, except +.BR sb , +are changeable with a remount, for example, but you can't change +.B gid +or +.B umask +for the +.IR fatfs ). +.PP +Mount by label or uuid will work only if your devices have the names listed in +.IR /proc/partitions . +In particular, it may well fail if the kernel was compiled with devfs +but devfs is not mounted. +.PP +It is possible that files +.IR /etc/mtab +and +.IR /proc/mounts +don't match. The first file is based only on the mount command options, but the +content of the second file also depends on the kernel and others settings (e.g. +remote NFS server. In particular case the mount command may reports unreliable +information about a NFS mount point and the /proc/mounts file usually contains +more reliable information.) +.PP +Checking files on NFS filesystem referenced by file descriptors (i.e. the +.BR fcntl +and +.BR ioctl +families of functions) may lead to inconsistent result due to the lack of +consistency check in kernel even if noac is used. +.SH HISTORY +A +.B mount +command existed in Version 5 AT&T UNIX. +.SH AVAILABILITY +The mount command is part of the util-linux-ng package and is available from +ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/. + |