+.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