Linux "mount" Command Line Options and Examples
mount a filesystem

All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree.


mount [-l|-h|-V]

    mount -a [-fFnrsvw] [-t fstype] [-O optlist]

    mount [-fnrsvw] [-o options] device|dir

    mount [-fnrsvw] [-t fstype] [-o options] device dir

Command Line Options:

Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). Thefilesystems are mounted following their order in fstab.Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify.
mount -a ...
Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mounts.
mount -B ...
Don't canonicalize paths. The mount command canonicalizes all paths (from command line or fstab) by default. This option canbe used together with the -f flag for already canonicalized absolute paths. The option is designed for mount helpers whichcall mount -i. It is strongly recommended to not use this command-line option for normal mount operations.Note that mount(8) does not pass this option to the /sbin/mount.type helpers.
mount -c ...
(Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on differentdevices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts go in parallel. Adisadvantage is that the mounts are done in undefined order. Thus, you cannot use this option if you want to mount both /usrand /usr/spool.
mount -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 -v flag to determine what the mount command is trying to do. It can also beused to add entries for devices that were mounted earlier with the -n option. The -f option checks for an existing record in/etc/mtab and fails when the record already exists (with a regular non-fake mount, this check is done by the kernel).
mount -f ...
Don't call the /sbin/mount.filesystem helper even if it exists.
mount -i ...
Mount the partition that has the specified label.
mount -L ...
Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this towork. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or forreiserfs using reiserfstune(8).
mount -l ...
Move a subtree to some other place. See above, the subsection The move operation.
mount -M ...
Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem.
mount -n ...
Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is use‐less without -a. For example, the command:mount -a -O no_netdevmounts all filesystems except those which have the option _netdev specified in the options field in the /etc/fstab file.It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negatethe rest.The -t and -O options are cumulative in effect; that is, the commandmount -a -t ext2 -O _netdevmounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option spec‐ified.
mount -O ...
Use the specified mount options. The opts argument is a comma-separated list. For example:mount LABEL=mydisk -o noatime,nodev,nosuidFor more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
mount -o ...
Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above,the subsection Bind mounts.
mount -R ...
Mount the filesystem read-only. A synonym is -o ro.Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For exam‐ple, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want tomount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see theblockdev(8) command.
mount -r ...
If only one argument for the mount command is given then the argument might be interpreted as target (mountpoint) or source(device). This option allows to explicitly define that the argument is the mount source.
mount --source ...
If only one argument for the mount command is given then the argument might be interpreted as target (mountpoint) or source(device). This option allows to explicitly define that the argument is the mount target.
mount --target ...
Specifies an alternative fstab file. If path is a directory then the files in the directory are sorted by strverscmp(3);files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. Thisoption is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard systemconfiguration.Note that mount(8) does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab fileswill be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab toverify the user's rights.
mount -T ...
The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supporteddepend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of thefilesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs.The programs mount and umount support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example'fuse.sshfs'. It's recommended to use subtype notation rather than add any prefix to the mount source (for example'' is deprecated).If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. Mount uses the blkidlibrary for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read thefile /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried,except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *,mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount optionsilent.The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probeorder (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader.More than one type may be specified in a comma-separated list, for option -t as well as in an /etc/fstab entry. The list offilesystem types for option -t can be prefixed with no to specify the filesystem types on which no action should be taken.The prefix no has no effect when specified in an /etc/fstab entry.The prefix no can be meaningful with the -a option. For example, the commandmount -a -t nomsdos,smbfsmounts all filesystems except those of type msdos and smbfs.For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of thefilesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. Thenfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all typesin a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since differ‐ent versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script thatsets up the desired call.
mount -t ...
Mount the partition that has the specified uuid.
mount -U ...
Mount the filesystem read/write. The read-write is kernel default. A synonym is -o rw.Note that specify -w on command line forces mount command to never try read-only mount on write-protected devices. The defaultis try read-only if the previous mount syscall with read-write flags failed.
mount -w ...
Display version information and exit.
mount -V ...
Display help text and exit.FILESYSTEM-INDEPENDENT MOUNT OPTIONSSome of these options are only useful when they appear in the /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. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output forextN filesystems).The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them – e.g., the syncoption today has an effect only for ext2, ext3, fat, vfat and ufs):async All I/O to the filesystem should be done asynchronously. (See also the sync option.)atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of therelatime and strictatime mount options.noatimeDo not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). Thisworks for all inode types (directories too), so it implies Can be mounted with the -a option.noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted).context=context, fscontext=context, defcontext=context, and rootcontext=contextThe context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard diskformatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 formatted disk from a non-SELinuxworkstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibilitywith xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time nothaving to label every file by assigning the entire disk one security context.A commonly used option for removable media is context="system_u:object_r:removable_t".Two other options are fscontext= and defcontext=, both of which are mutually exclusive of the context option. This means youcan use fscontext and defcontext with each other, but neither can be used with context.The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarchingfilesystem 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. Individualfile labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate con‐text that fscontext provides, in addition to supplying the same label for individual files.You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unla‐beled files in the policy and requires a filesystem that supports xattr labeling.The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomesvisible to userspace. This was found to be useful for things like stateless linux.Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current con‐text.Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount(8) willinterpret the comma as a separator between mount options. Don't forget that the shell strips off quotes and thus double quot‐ing is required. For example:mount -t tmpfs none /mnt -o \'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'For more details, see selinux(8).defaultsUse the default options: rw, suid, dev, exec, auto, nouser, and async.Note that the real set of all default mount options depends on kernel and filesystem type. See the beginning of this sectionfor more Interpret character or block special devices on the filesystem.nodev Do not interpret character or block special devices on the file system.diratimeUpdate directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.)nodiratimeDo not update directory inode access times on this filesystem. (This option is implied when noatime is set.)dirsyncAll directory updates within the filesystem should be done synchronously. This affects the following system calls: creat,link, unlink, symlink, mkdir, rmdir, mknod and rename.exec Permit execution of binaries.noexec Do not permit direct execution of any binaries on the mounted Allow an ordinary user to mount the filesystem if one of that user's groups matches the group of the device. This optionimplies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid).iversionEvery time the inode is modified, the i_version field will be incremented.noiversionDo not increment the i_version inode field.mand Allow mandatory locks on this filesystem. See fcntl(2).nomand Do not allow mandatory locks on this filesystem._netdevThe filesystem resides on a device that requires network access (used to prevent the system from attempting to mount thesefilesystems until the network has been enabled on the system).nofail Do not report errors for this device if it does not exist.relatimeUpdate inode access times relative to modify or change time. Access time is only updated if the previous access time was ear‐lier than the current modify or change time. (Similar to noatime, but it doesn't break mutt or other applications that needto know if a file has been read since the last time it was modified.)Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and thestrictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the file's last access timeis always updated if it is more than 1 day old.norelatimeDo not use the relatime feature. See also the strictatime mount option.strictatimeAllows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime butstill allow userspace to override it. For more details about the default system mount options see /proc/mounts.nostrictatimeUse the kernel's default behavior for inode access time updates.lazytimeOnly update times (atime, mtime, ctime) on the in-memory version of the file inode.This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preal‐located files.The on-disk timestamps are updated only when:
mount -h ...
the inode needs to be updated for some change unrelated to file timestamps
mount - ...
Allow to make a target directory (mountpoint). The optional argument mode specifies the filesystem access mode used formkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users. The option isalso supported as x-mount.mkdir, this notation is deprecated for mount.mkdir since v2.30.FILESYSTEM-SPECIFIC MOUNT OPTIONSThe following options apply only to certain filesystems. We sort them by filesystem. They all follow the -o flag.What options are supported depends a bit on the running kernel. More info may be found in the kernel source subdirectory Documenta‐tion/filesystems.Mount options for adfsuid=value and gid=valueSet the owner and group of the files in the filesystem (default: uid=gid=0).ownmask=value and othmask=valueSet the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respec‐tively). See also /usr/src/linux/Documentation/filesystems/adfs.txt.Mount options for affsuid=value and gid=valueSet the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value,the UID and GID of the current process are taken).setuid=value and setgid=valueSet the owner and group of all files.mode=valueSet the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories thathave read permission. The value is given in octal.protectDo not allow any changes to the protection bits on the filesystem.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 thenclear this option. Strange...verbosePrint an informational message for each successful mount.prefix=stringPrefix used before volume name, when following a link.volume=stringPrefix (of length at most 30) used before '/' when following a symbolic link.reserved=value(Default: 2.) Number of unused blocks at the start of the device.root=valueGive explicitly the location of the root blocksize. Allowed values are 512, 1024, 2048, 4096.grpquota|noquota|quota|usrquotaThese options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.)Mount options for btrfsBtrfs is a copy-on-write filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, repair, andeasy administration.alloc_start=bytesDebugging option to force all block allocations above a certain byte threshold on each block device. The value is specifiedin bytes, optionally with a K, M, or G suffix, case insensitive. Default is 1MB.autodefragDisable/enable auto defragmentation. Auto defragmentation detects small random writes into files and queues them up for thedefrag process. Works best for small files; not well-suited for large database workloads.check_int|check_int_data|check_int_print_mask=valueThese debugging options control the behavior of the integrity checking module(the BTRFS_FS_CHECK_INTEGRITY config optionrequired).check_int enables the integrity checker module, which examines all block-write requests to ensure on-disk consistency, at alarge memory and CPU cost.check_int_data includes extent data in the integrity checks, and implies the check_int option.check_int_print_mask takes a bitmask of BTRFSIC_PRINT_MASK_* values as defined in fs/btrfs/check-integrity.c, to control theintegrity checker module behavior.See comments at the top of fs/btrfs/check-integrity.c for more info.commit=secondsSet the interval of periodic commit, 30 seconds by default. Higher values defer data being synced to permanent storage, withobvious consequences when the system crashes. The upper bound is not forced, but a warning is printed if it's more than 300seconds (5 minutes).compress|compress=type|compress-force|compress-force=typeControl BTRFS file data compression. Type may be specified as "zlib" "lzo" or "no" (for no compression, used for remounting).If no type is specified, zlib is used. If compress-force is specified, all files will be compressed, whether or not they com‐press well. If compression is enabled, nodatacow and nodatasum are disabled.degradedAllow mounts to continue with missing devices. A read-write mount may fail with too many devices missing, for example if astripe member is completely missing.device=devicepathSpecify a device during mount so that ioctls on the control device can be avoided. Especially useful when trying to mount amulti-device setup as root. May be specified multiple times for multiple devices.discardDisable/enable the discard mount option. The discard function issues frequent commands to let the block device reclaim spacefreed by the filesystem. This is useful for SSD devices, thinly provisioned LUNs and virtual machine images, but may have asignificant performance impact. (The fstrim command is also available to initiate batch trims from userspace.)enospc_debugDisable/enable debugging option to be more verbose in some ENOSPC conditions.fatal_errors=actionAction to take when encountering a fatal error:"bug" - BUG() on a fatal error. This is the default."panic" - panic() on a fatal error.flushoncommitThe flushoncommit mount option forces any data dirtied by a write in a prior transaction to commit as part of the current com‐mit. This makes the committed state a fully consistent view of the filesystem from the application's perspective (i.e., itincludes all completed filesystem operations). This was previously the behavior only when a snapshot is created.inode_cacheEnable free inode number caching. Defaults to off due to an overflow problem when the free space CRCs don't fit inside asingle page.max_inline=bytesSpecify the maximum amount of space, in bytes, that can be inlined in a metadata B-tree leaf. The value is specified inbytes, optionally with a K, M, or G suffix, case insensitive. In practice, this value is limited by the root sector size,with some space unavailable due to leaf headers. For a 4k sectorsize, max inline data is ~3900 bytes.metadata_ratio=valueSpecify that 1 metadata chunk should be allocated after every value data chunks. Off by default.noacl Enable/disable support for Posix Access Control Lists (ACLs). See the acl(5) manual page for more information about ACLs.nobarrierEnable/disable the use of block-layer write barriers. Write barriers ensure that certain IOs make it through the device cacheand are on persistent storage. If disabled on a device with a volatile (non-battery-backed) write-back cache, the nobarrieroption will lead to filesystem corruption on a system crash or power loss.nodatacowEnable/disable data copy-on-write for newly created files. This option implies nodatasum, and disables all compression.nodatasumEnable/disable data checksumming for newly created files. This option implies datacow.notreelogEnable/disable the tree logging used for fsync and O_SYNC writes.recoveryEnable autorecovery attempts if a bad tree root is found at mount time. Currently this scans a list of several previous treeroots and tries to use the first readable.rescan_uuid_treeForce check and rebuild procedure of the UUID tree. This should not normally be needed.skip_balanceSkip automatic resume of an interrupted balance operation after mount. May be resumed with "btrfs balance resume."nospace_cacheDisable freespace cache loading without clearing the cache.clear_cacheForce clearing and rebuilding of the disk space cache if something has gone wrong.ssd|nossd|ssd_spreadOptions to control ssd allocation schemes. By default, BTRFS will enable or disable ssd allocation heuristics depending onwhether a rotational or non-rotational disk is in use. The ssd and nossd options can override this autodetection.The ssd_spread mount option attempts to allocate into big chunks of unused space, and may perform better on low-end ssds.ssd_spread implies ssd, enabling all other ssd heuristics as well.subvol=pathMount subvolume at path rather than the root subvolume. The path is relative to the top level subvolume.subvolid=IDMount subvolume specified by an ID number rather than the root subvolume. This allows mounting of subvolumes which are not inthe root of the mounted filesystem. You can use "btrfs subvolume list" to see subvolume ID numbers.subvolrootid=objectid (deprecated)Mount subvolume specified by objectid rather than the root subvolume. This allows mounting of subvolumes which are not in theroot of the mounted filesystem. You can use "btrfs subvolume show " to see the object ID for a subvolume.thread_pool=numberThe number of worker threads to allocate. The default number is equal to the number of CPUs + 2, or 8, whichever is smaller.user_subvol_rm_allowedAllow subvolumes to be deleted by a non-root user. Use with caution.Mount options for cifsSee the options section of the mount.cifs(8) man page (cifs-utils package must be installed).Mount options for coherentNone.Mount options for debugfsThe debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has thefollowing options:uid=n, gid=nSet the owner and group of the mountpoint.mode=valueSets the mode of the mountpoint.Mount options for devptsThe devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a processopens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can beaccessed as /dev/pts/<number>.uid=value and gid=valueThis sets the owner or the group of newly created PTYs to the specified values. When nothing is specified, they will be setto the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly cre‐ated PTYs to belong to the tty group.mode=valueSet the mode of newly created PTYs to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y"the default on newly created PTYs.newinstanceCreate a private instance of devpts filesystem, such that indices of ptys allocated in this new instance are independent ofindices created in other instances of devpts.All mounts of devpts without this newinstance option share the same set of pty indices (i.e legacy mode). Each mount ofdevpts with the 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 startingwith 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configura‐tion.To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt inthe linux kernel source tree for details.ptmxmode=valueSet the mode for the new ptmx device node in the devpts filesystem.With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in theroot of the devpts filesystem (typically /dev/pts/ptmx).For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifiesa more useful mode for the ptmx node and is highly recommended when the 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 CON‐FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration.Mount options for ext2, ext3 and ext4See the options section of the ext2(5), ext3(5) or ext4(5) man page (the e2fsprogs package must be installed).Mount options for fat(Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.)blocksize={512|1024|2048}Set blocksize (default 512). This option is obsolete.uid=value and gid=valueSet the owner and group of all files. (Default: the UID and GID of the current process.)umask=valueSet the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. Thevalue is given in octal.dmask=valueSet the umask applied to directories only. The default is the umask of the current process. The value is given in octal.fmask=valueSet the umask applied to regular files only. The default is the umask of the current process. The value is given in octal.allow_utime=valueThis option controls the permission check of mtime/atime.20 If current process is in group of file's group ID, you can change timestamp.2 Other users can change timestamp.The default is set from `dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022)Normally utime(2) checks current process is owner of the file, or it has CAP_FOWNER capability. But FAT filesystem doesn'thave UID/GID on disk, so normal check is too inflexible. With this option you can relax it.check=valueThree different levels of pickyness can be chosen:r[elaxed]Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes very‐, leading and embedded spaces are accepted in each name part (name and extension).n[ormal]Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default.s[trict]Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are notaccepted by MS-DOS (+, =, etc.) are rejected.codepage=valueSets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used.conv=modeThis option is obsolete and may fail or being ignored.cvf_format=moduleForces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supportskmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete.cvf_option=optionOption passed to the CVF module. This option is obsolete.debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed ifthe parameters appear to be inconsistent).discardIf set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devicesand sparse/thinly-provisioned LUNs.dos1xfloppyIf set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parametersmatch defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.errors={panic|continue|remount-ro}Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode(default behavior).fat={12|16|32}Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution!iocharset=valueCharacter set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Longfilenames are stored on disk in Unicode format.nfs={stale_rw|nostale_ro}Enable this only if you want to export the FAT filesystem over NFS.stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result inspurious ESTALE errors.nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry.This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operationssuch as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file,potentially causing data corruption. For this reason, this option also mounts the filesystem readonly.To maintain backward compatibility, '-o nfs' is also accepted, defaulting to This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux usesinternally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoidthe pitfalls of local time.time_offset=minutesSet offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each time‐stamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2)is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases inpresence of DST - time stamps in a different DST setting will be off by one hour.quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution!rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only byapplications as a flag (e.g. it's set for the customized folder).If you want to use ATTR_RO as read-only flag even for the directory, set this option.showexecIf 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.sys_immutableIf set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default.flush If set, the filesystem will try to flush to disk more early than normal. Not set by default.usefreeUse 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 clus‐ters" on FSINFO is correct, by this option you can avoid scanning disk.dots, nodots, dotsOK=[yes|no]Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem.Mount options for hfscreator=cccc, type=ccccSet the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'.uid=n, gid=nSet the owner and group of all files. (Default: the UID and GID of the current process.)dir_umask=n, file_umask=n, umask=nSet the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the currentprocess.session=nSelect the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with any‐thing but a CDROM as underlying device.part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all.quiet Don't complain about invalid mount options.Mount options for hpfsuid=value and gid=valueSet the owner and group of all files. (Default: the UID and GID of the current process.)umask=valueSet the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. Thevalue is given in{lower|asis}Convert all files names to lower case, or leave them. (Default: case=lower.)conv=modeThis option is obsolete and may fail or being ignored.nocheckDo not abort mounting when certain consistency checks fail.Mount options for iso9660ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. Seealso the udf filesystem.)Normal iso9660 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters arein 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 direc‐tory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from anormal UNIX filesystem (except that it is read-only, of course).norock Disable the use of Rock Ridge extensions, even if available. Cf. map.nojolietDisable the use of Microsoft Joliet extensions, even if available. Cf. map.check={r[elaxed]|s[trict]}With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningfultogether with norock and map=normal. (Default: check=strict.)uid=value and gid=valueGive all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridgeextensions. (Default: uid=0,gid=0.)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 map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but alsoapply Acorn extensions if present.mode=valueFor non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octalmode values require a leading 0.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.)block={512|1024|2048}Set the block size to the indicated value. (Default: block=1024.)conv=modeThis option is obsolete and may fail or being ignored.cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the filelength. This implies that a file cannot be larger than 16 MB.session=xSelect number of session on multisession CD.sbsector=xxxSession begins from sector xxx.The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsoft's Jolietextensions.iocharset=valueCharacter set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1.utf8 Convert 16 bit Unicode characters on CD to UTF-8.Mount options for jfsiocharset=nameCharacter set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file.resize=valueResize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during aremount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of thepartition.nointegrityDo not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume frombackup media. The integrity of the volume is not guaranteed if the system abnormally ends.integrityDefault. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previ‐ously specified in order to restore normal behavior.errors={continue|remount-ro|panic}Define the behavior 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.)noquota|quota|usrquota|grpquotaThese options are accepted but ignored.Mount options for minixNone.Mount options for msdosSee mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only.The filesystem can be made writable again by remounting it.Mount options for ncpfsJust like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount system call. This argumentis constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs.Mount options for nfs and nfs4See the options section of the nfs(5) man page (the nfs-utils package must be installed).The nfs and nfs4 implementation expects a binary argument (a struct nfs_mount_data) to the mount system call. This argument is con‐structed by mount.nfs(8) and the current version of mount (2.13) does not know anything about nfs and nfs4.Mount options for ntfsiocharset=nameCharacter set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters.Deprecated.nls=nameNew name for the option earlier called iocharset.utf8 Use UTF-8 for converting file names.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, usevfat-style 4-byte escape sequences starting with ":". Here 2 give a little-endian encoding and 1 a byteswapped bigendianencoding.posix=[0|1]If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hardlinks instead of being suppressed. This option is obsolete.uid=value, gid=value and umask=valueSet the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root andnot readable by somebody else.Mount options for overlaySince Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems.An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems,the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directo‐ries, merged with the upper object.The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even beanother overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extendedattributes, and must provide a valid d_type in readdir responses, so NFS is not suitable.A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into amerged directory by using:mount -t overlay overlay \
mount -mount.mkdir[ ...
lowerdir=directoryAny filesystem, does not need to be on a writable filesystem.upperdir=directoryThe upperdir is normally on a writable filesystem.workdir=directoryThe workdir needs to be an empty directory on the same filesystem as upperdir.Mount options for procuid=value and gid=valueThese options are recognized, but have no effect as far as I can see.Mount options for ramfsRamfs is a memory based filesystem. Mount it and you have it. Unmount it and it is gone. There are no mount options.Mount options for reiserfsReiserfs is a journaling filesystem.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.hash={rupasov|tea|r5|detect}Choose which hash function reiserfs will use to find files within directories.rupasovA hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names toclose hash values. This option should not be used, as it causes a high probability of hash collisions.tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high ran‐domness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errorsare experienced with the r5 hash.r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has hugedirectories and unusual file-name patterns.detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write thisinformation into the reiserfs superblock. This is only useful on the first mount of an old format filesystem.hashed_relocationTunes the block allocator. This may provide performance improvements in some situations.no_unhashed_relocationTunes the block allocator. This may provide performance improvements in some situations.noborderDisable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situa‐tions.nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfs'sfast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save foractual writes into its journaling area. Implementation of nolog is a work in progress.notail By default, reiserfs stores small files and `file tails' directly into its tree. This confuses some utilities such asLILO(8). This option is used to disable packing of files into the tree.replayonlyReplay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck.resize=numberA remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has num‐ber blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a specialresizer utility which can be obtained from Extended User Attributes. See the attr(5) manual page.acl Enable POSIX Access Control Lists. See the acl(5) manual page.barrier=none / barrier=flushThis disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables(default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, itwill disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, makingvolatile 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.Mount options for romfsNone.Mount options for squashfsNone.Mount options for smbfsJust like nfs, the smbfs implementation expects a binary argument (a struct smb_mount_data) to the mount system call. This argumentis constructed by smbmount(8) and the current version of mount (2.12) does not know anything about smbfs.Mount options for sysvNone.Mount options for tmpfssize=nbytesOverride default maximum size of the filesystem. The size is given in bytes, and rounded up to entire pages. The default ishalf of the memory. The size parameter also accepts a suffix % to limit this tmpfs instance to that percentage of your physi‐cal RAM: the default, when neither size nor nr_blocks is specified, is size=50%nr_blocks=The same as size, but in blocks of PAGE_CACHE_SIZEnr_inodes=The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on amachine with highmem) the number of lowmem RAM pages, whichever is the lower.The tmpfs mount options for sizing (size, nr_blocks, and nr_inodes) accept a suffix k, m or g for Ki, Mi, Gi (binary kilo (kibi),binary mega (mebi) and binary giga (gibi)) and can be changed on remount.mode= Set initial permissions of the root directory.uid= The user id.gid= The group id.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 beadjusted on the fly via 'mount -o remount ...'defaultprefers to allocate memory from the local nodeprefer:Nodeprefers to allocate memory from the given Nodebind:NodeListallocates memory only from nodes in NodeListinterleaveprefers to allocate from each node in turninterleave:NodeListallocates from each node of NodeList in turn.The NodeList format is a comma-separated list of decimal numbers and ranges, a range being two "hyphen-minus"-separated deci‐mal numbers, the smallest and largest node numbers in the range. For example, mpol=bind:0–3,5,7,9–15Note that trying to mount a tmpfs with an mpol option will fail if the running kernel does not support NUMA; and will fail ifits nodelist specifies a node which is not online. If your system relies on that tmpfs being mounted, but from time to timeruns a kernel built without NUMA capability (perhaps a safe recovery kernel), or with fewer nodes online, then it is advisableto 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'.Mount options for ubifsUBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off.The device name may be specified asubiX_Y UBI device number X, volume number YubiY UBI device number 0, volume number YubiX:NAMEUBI device number X, volume with name NAMEubi:NAMEUBI device number 0, volume with name NAMEAlternative ! separator may be used instead of :.The following mount options are available:bulk_readEnable bulk-read. VFS read-ahead is disabled because it slows down the file system. Bulk-Read is an internal optimization.Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND cando "read-while-load" if it reads more than one NAND page.no_bulk_readDo not bulk-read. This is the default.chk_data_crcCheck data CRC-32 checksums. This is the default.no_chk_data_crc.Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it doescheck it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculatedwhen writing the data.compr={none|lzo|zlib}Select the default compressor which is used when new files are written. It is still possible to read compressed files ifmounted with the none option.Mount options for udfudf is the "Universal Disk Format" filesystem defined by the Optical Storage Technology Association, and is often used for DVD-ROM.See also iso9660.gid= Set the default group.umask= Set the default umask. The value is given in octal.uid= Set the default user.unhide Show otherwise hidden files.undeleteShow deleted files in lists.nostrictUnset strict conformance.iocharsetSet the NLS character Set the block size. (May not work unless 2048.)novrs Skip volume sequence recognition.session=Set the CDROM session counting from 0. Default: last session.anchor=Override standard anchor location. Default: 256.volume=Override the VolumeDesc location. (unused)partition=Override the PartitionDesc location. (unused)lastblock=Set the last block of the filesystem.fileset=Override the fileset block location. (unused)rootdir=Override the root directory location. (unused)Mount options for ufsufstype=valueUFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Featuresof some implementations are undocumented, so its hard to recognize the type of ufs automatically. That's why the user mustspecify the type of ufs by mount option. Possible values are:old Old format of ufs, this is the default, read only. (Don't forget to give the -r option.)44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).ufs2 Used in FreeBSD 5.x supported as read-write.5xbsd Synonym for ufs2.sun For filesystems created by SunOS or Solaris on Sparc.sunx86 For filesystems created by Solaris on x86.hp For filesystems created by HP-UX, read-only.nextstepFor filesystems created by NeXTStep (on NeXT station) (currently read only).nextstep-cdFor NextStep CDROMs (block_size == 2048), read-only.openstepFor filesystems created by OpenStep (currently read only). The same filesystem type is also used by Mac OS X.onerror=valueSet behavior on error:panic If an error is encountered, cause a kernel panic.[lock|umount|repair]These mount options don't do anything at present; when an error is encountered only a console message is printed.Mount options for umsdosSee mount options for msdos. The dotsOK option is explicitly killed by umsdos.Mount options for vfatFirst of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there areuni_xlateTranslate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are cre‐ated with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape characteris ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicodecharacter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).posix Allow two files with names that only differ in case. This option is obsolete.nonumtailFirst try to make a short name without sequence number, before trying name~num.ext.utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem withthis option or disabled with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets disabled.shortname=modeDefines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists,it will always be the preferred one for display. There are four modes:lower Force the short name to lower case upon display; store a long name when the short name is not all upper case.win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case.winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case.mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the defaultsince Linux 2.6.32.Mount options for usbfsdevuid=uid and devgid=gid and devmode=modeSet the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode isgiven in octal.busuid=uid and busgid=gid and busmode=modeSet the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode isgiven in octal.listuid=uid and listgid=gid and listmode=modeSet the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal.Mount options for xenixNone.Mount options for xfsSee the options section of the xfs(5) man page (the xfsprogs package must be installed).THE LOOP DEVICEOne further possible type is a mount via the loop device. For example, the commandmount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt.If no explicit loop device is mentioned (but just an option `-o loop' is given), then mount will try to find some unused loop deviceand use that, for examplemount /tmp/disk.img /mnt -o loopThe mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem isknown for libblkid, for example:mount /tmp/disk.img /mntmount -t ext3 /tmp/disk.img /mntThis type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (Theseoptions can be used in addition to those specific to the filesystem type.)Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed byumount independently of /etc/mtab.You can also free a loop device by hand, using losetup -d or umount -d.Since util-linux v2.29 mount command re-uses the loop device rather than initialize a new device if the same backing file is alreadyused for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption.RETURN CODESmount has the following return codes (the bits can be ORed):0 success1 incorrect invocation or permissions2 system error (out of memory, cannot fork, no more loop devices)4 internal mount bug8 user interrupt16 problems writing or locking /etc/mtab32 mount failure64 some mount succeededThe command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded).EXTERNAL HELPERSThe syntax of external mount helpers is:/sbin/mount.suffix spec dir [-sfnv] [-o options] [-t type.subtype]where the suffix is the filesystem type and the -sfnvo options have the same meaning as the normal mount options. The -t option isused for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto,noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated listas argument to the -o option.FILES/etc/fstab filesystem table/etc/mtab table of mounted filesystems/etc/mtab~ lock file/etc/mtab.tmp temporary file/etc/filesystems a list of filesystem types to tryENVIRONMENTLIBMOUNT_FSTAB=<path>overrides the default location of the fstab file (ignored for suid)LIBMOUNT_MTAB=<path>overrides the default location of the mtab file (ignored for suid)LIBMOUNT_DEBUG=allenables libmount debug outputLIBBLKID_DEBUG=allenables libblkid debug outputLOOPDEV_DEBUG=allenables loop device setup debug output
mount -olowerdir=/lower,upperdir=/upper,workdir=/work ...