+.BI \-M " last-mounted-directory"
+Set the last-mounted directory for the filesystem.
+.TP
+.BR \-o " [^]\fImount-option\fR[,...]"
+Set or clear the indicated default mount options in the filesystem.
+Default mount options can be overridden by mount options specified
+either in
+.BR /etc/fstab (5)
+or on the command line arguments to
+.BR mount (8).
+Older kernels may not support this feature; in particular,
+kernels which predate 2.4.20 will almost certainly ignore the
+default mount options field in the superblock.
+.IP
+More than one mount option can be cleared or set by separating
+features with commas. Mount options prefixed with a
+caret character ('^') will be cleared in the filesystem's superblock;
+mount options without a prefix character or prefixed with a plus
+character ('+') will be added to the filesystem.
+.IP
+The following mount options can be set or cleared using
+.BR tune2fs :
+.RS 1.2i
+.TP
+.B debug
+Enable debugging code for this filesystem.
+.TP
+.B bsdgroups
+Emulate BSD behavior when creating new files: they will take the group-id
+of the directory in which they were created. The standard System V behavior
+is the default, where newly created files take on 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
+.B user_xattr
+Enable user-specified extended attributes.
+.TP
+.B acl
+Enable Posix Access Control Lists.
+.TP
+.B uid16
+Disables 32-bit UIDs and GIDs. This is for interoperability with
+older kernels which only store and expect 16-bit values.
+.TP
+.B journal_data
+When the filesystem is mounted with journalling enabled, all data
+(not just metadata) is committed into the journal prior to being written
+into the main filesystem.
+.TP
+.B journal_data_ordered
+When the filesystem is mounted with journalling enabled, all data is forced
+directly out to the main file system prior to its metadata being committed
+to the journal.
+.TP
+.B journal_data_writeback
+When the filesystem is mounted with journalling enabled, data may be
+written into the main filesystem after its metadata has been committed
+to the journal. This may increase throughput, however, it may allow old
+data to appear in files after a crash and journal recovery.
+.TP
+.B nobarrier
+The file system will be mounted with barrier operations in the journal
+disabled. (This option is currently only supported by the ext4 file
+system driver in 2.6.35+ kernels.)
+.TP
+.B block_validity
+The file system will be mounted with the block_validity option enabled,
+which causes extra checks to be performed after reading or writing from
+the file system. This prevents corrupted metadata blocks from causing
+file system damage by overwriting parts of the inode table or block
+group descriptors. This comes at the cost of increased memory and CPU
+overhead, so it is enabled only for debugging purposes. (This option is
+currently only supported by the ext4 file system driver in 2.6.35+
+kernels.)
+.TP
+.B discard
+The file system will be mounted with the discard mount option. This will
+cause the file system driver to attempt to use the trim/discard feature
+of some storage devices (such as SSD's and thin-provisioned drives
+available in some enterprise storage arrays) to inform the storage
+device that blocks belonging to deleted files can be reused for other
+purposes. (This option is currently only supported by the ext4 file
+system driver in 2.6.35+ kernels.)
+.TP
+.B nodelalloc
+The file system will be mounted with the nodelalloc mount option. This
+will disable the delayed allocation feature. (This option is currently
+only supported by the ext4 file system driver in 2.6.35+ kernels.)
+.RE
+.TP
+.BR \-O " [^]\fIfeature\fR[,...]"
+Set or clear the indicated filesystem features (options) in the filesystem.
+More than one filesystem feature can be cleared or set by separating
+features with commas. Filesystem features prefixed with a
+caret character ('^') will be cleared in the filesystem's superblock;
+filesystem features without a prefix character or prefixed with a plus
+character ('+') will be added to the filesystem. For a detailed
+description of the file system features, please see the man page
+.BR ext4 (5).
+.IP
+The following filesystem features can be set or cleared using
+.BR tune2fs :
+.RS 1.2i
+.TP
+.B dir_index
+Use hashed b-trees to speed up lookups for large directories.
+.TP
+.B dir_nlink
+Allow more than 65000 subdirectories per directory.
+.TP
+.B extent
+Enable the use of extent trees to store the location of data blocks in inodes.
+.TP
+.B extra_isize
+Enable the extended inode fields used by ext4.
+.TP
+.B filetype
+Store file type information in directory entries.
+.TP
+.B flex_bg
+Allow bitmaps and inode tables for a block group to be placed
+anywhere on the storage media. \fBTune2fs\fR will not reorganize
+the location of the inode tables and allocation bitmaps, as
+.BR mke2fs (8)
+will do when it creates a freshly formatted file system with
+.B flex_bg
+enabled.
+.TP
+.B has_journal
+Use a journal to ensure filesystem consistency even across unclean shutdowns.
+Setting the filesystem feature is equivalent to using the
+.B \-j
+option.
+.TP
+.B huge_file
+Support files larger than 2 terabytes in size.
+.TP
+.B large_file
+Filesystem can contain files that are greater than 2GB.
+.TP
+.B resize_inode
+Reserve space so the block group descriptor table may grow in the
+future.
+.B Tune2fs
+only supports clearing this filesystem feature.
+.TP
+.B mmp
+Enable or disable multiple mount protection (MMP) feature.
+@QUOTA_MAN_COMMENT@.TP
+@QUOTA_MAN_COMMENT@.B quota
+@QUOTA_MAN_COMMENT@Enable internal file system quota inodes.
+.TP
+.B sparse_super
+Limit the number of backup superblocks to save space on large filesystems.
+.TP
+.B uninit_bg
+Allow the kernel to initialize bitmaps and inode tables lazily, and to
+keep a high watermark for the unused inodes in a filesystem, to reduce
+.BR e2fsck (8)
+time. This first e2fsck run after enabling this feature will take the
+full time, but subsequent e2fsck runs will take only a fraction of the
+original time, depending on how full the file system is.
+.RE
+.IP
+After setting or clearing
+.BR sparse_super ,
+.BR uninit_bg ,
+.BR filetype ,
+or
+.B resize_inode
+filesystem features,
+.BR e2fsck (8)
+must be run on the filesystem to return the filesystem to a consistent state.
+.B Tune2fs
+will print a message requesting that the system administrator run
+.BR e2fsck (8)
+if necessary. After setting the
+.B dir_index
+feature,
+.B e2fsck -D
+can be run to convert existing directories to the hashed B-tree format.
+Enabling certain filesystem features may prevent the filesystem from being
+mounted by kernels which do not support those features. In particular, the
+.BR uninit_bg
+and
+.BR flex_bg
+features are only supported by the ext4 filesystem.
+.TP
+.BI \-p " mmp_check_interval"
+Set the desired MMP check interval in seconds. It is 5 seconds by default.
+.TP
+.BI \-r " reserved-blocks-count"
+Set the number of reserved filesystem blocks.
+.TP
+.BI \-Q " quota-options"
+Sets 'quota' feature on the superblock and works on the quota files for the
+given quota type. Quota options could be one or more of the following:
+.RS 1.2i
+.TP
+.BR [^]usrquota
+Sets/clears user quota inode in the superblock.
+.TP
+.BR [^]grpquota
+Sets/clears group quota inode in the superblock.
+.RE
+.TP
+.BI \-T " time-last-checked"
+Set the time the filesystem was last checked using
+.BR e2fsck .
+The time is interpreted using the current (local) timezone.
+This can be useful in scripts which use a Logical Volume Manager to make
+a consistent snapshot of a filesystem, and then check the filesystem
+during off hours to make sure it hasn't been corrupted due to
+hardware problems, etc. If the filesystem was clean, then this option can
+be used to set the last checked time on the original filesystem. The format
+of
+.I time-last-checked
+is the international date format, with an optional time specifier, i.e.
+YYYYMMDD[HH[MM[SS]]]. The keyword
+.B now
+is also accepted, in which case the last checked time will be set to the
+current time.
+.TP
+.BI \-u " user"
+Set the user who can use the reserved filesystem blocks.
+.I user
+can be a numerical uid or a user name. If a user name is given, it
+is converted to a numerical uid before it is stored in the superblock.
+.TP
+.BI \-U " UUID"
+Set the universally unique identifier (UUID) of the filesystem to
+.IR UUID .
+The format of the UUID is a series of hex digits separated by hyphens,
+like this:
+"c1b9d5a2-f162-11cf-9ece-0020afc76f16".
+The
+.I UUID
+parameter may also be one of the following:
+.RS 1.2i
+.TP
+.I clear
+clear the filesystem UUID
+.TP
+.I random
+generate a new randomly-generated UUID
+.TP
+.I time
+generate a new time-based UUID
+.RE
+.IP
+The UUID may be used by
+.BR mount (8),
+.BR fsck (8),
+and
+.BR /etc/fstab (5)
+(and possibly others) by specifying
+.BI UUID= uuid
+instead of a block special device name like
+.BR /dev/hda1 .
+.IP
+See
+.BR uuidgen (8)
+for more information.
+If the system does not have a good random number generator such as
+.I /dev/random
+or
+.IR /dev/urandom ,
+.B tune2fs
+will automatically use a time-based UUID instead of a randomly-generated UUID.