/usr/local/bin/apps # df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/mtdblock2            9828      9828         0 100% /
mdev                     20948         0     20948   0% /dev
tmpfs                    20948        28     20920   0% /tmp
tmpfs                     1024        80       944   8% /var
/dev/nftl_dat0           39664      8036     29580  21% /media/localdata
/dev/nftl_usr0          148768    135936      5152  96% /usr
/dev/nftl0             1570816    194372   1376444  12% /media/usrdata

mount: invalid option -- h
BusyBox v1.8.2 (2009-04-17 16:52:19 CST) multi-call binary

Usage: mount [flags] DEVICE NODE [-o options,more-options]

Mount a filesystem. Filesystem autodetection requires /proc be mounted.

Options:
        -a              Mount all filesystems in fstab
        -r              Read-only mount
        -t fs-type      Filesystem type
        -w              Read-write mount (default)

-o option:
        loop            Ignored (loop devices are autodetected)
        [a]sync         Writes are asynchronous / synchronous
        [no]atime       Disable / enable updates to inode access times
        [no]diratime    Disable / enable atime updates to directories
        [no]dev         Allow use of special device files / disallow them
        [no]exec        Allow use of executable files / disallow them
        [no]suid        Allow set-user-id-root programs / disallow them
        [r]shared       Convert [recursively] to a shared subtree
        [r]slave        Convert [recursively] to a slave subtree
        [r]private      Convert [recursively] to a private subtree
        [un]bindable    Make mount point [un]able to be bind mounted
        bind            Bind a directory to an additional location
        move            Relocate an existing mount point
        remount         Remount a mounted filesystem, changing its flags
        ro/rw           Mount for read-only / read-write

There are EVEN MORE flags that are specific to each filesystem
You'll have to see the written documentation for those filesystems

文件系统读写：mount -o rw,remount /dev/nftl_usr0

文件系统只读：mount -o ro,remount /dev/nftl_usr0