ota_target_from_phone Error

[z12crypto]

root@xiaomao-virtual-machine:~/patchrom/nx612j# ../tools/releasetools/ota_target_from_phone -r
Wait for the device to be online...
Copy target file template into current working directory
Dump bootimage from device
adb: error: remote object 'ext4' does not exist
Extract recovery.fstab from device
mount: mounting /dev/block/mmcblk0p25 on /system failed: Device or resource busy
mount: can't find /data in /etc/fstab
Extract the whole /system from device