u0_a241@android:/ $ su
root@android:/ # ls
acct
cache
config
d
data
data_1
data_2
data_3
default.prop
dev
efs
etc
file_contexts
fstab.universal5410
init
init.goldfish.rc
init.rc
init.trace.rc
init.universal5410.rc
init.universal5410.usb.rc
init.usb.rc
init.wifi.rc
lib
lpm.rc
mnt
mnt_1
persdata
preload
proc
property_contexts
root
sbin
sdcard
seapp_contexts
sepolicy
storage
sys
system
ueventd.goldfish.rc
ueventd.rc
ueventd.universal5410.rc
vendor
root@android:/ # cd mnt
root@android:/mnt # ls
UsbDriveA
UsbDriveB
UsbDriveC
UsbDriveD
UsbDriveE
UsbDriveF
asec
extSdCard
obb
sdcard
secure
shell
root@android:/mnt # cd extSdCard
root@android:/mnt/extSdCard # ls
root@android:/mnt/extSdCard #
root@android:/mnt/extSdCard # cd ..
root@android:/mnt # mount -o rw mnt/extSdCard
Usage: mount [-r] [-w] [-o options] [-t type] device directory
1|root@android:/mnt # unmount
sh: unmount: not found
127|root@android:/mnt #
Even there is not unmount command:(
Any more advice to me guys?