[Snappy ubuntu core ]issues while extracting:

[Pillar Zuo]

Hi all
    I try to follow the guid :https://developer.ubuntu.com/en/snappy/porting/  to port Snappy to pcDuino V3,I think it maybe has some problem.
1,First linux order was wrong,you need replace "---" to "--".
2,After  I download devices.tar.xz file ,when I execute first linux order ,it report  error.
pillar at ubuntu:~$ sudo ubuntu-device-flash core -o my-snappy.img --size 4 --channel ubuntu-core/devel --device generic_armhf --platform am335x-boneblack --enable-ssh --device-part=./devices.tar.xz 
Fetching information from server... 
Downloading and setting up... 
96.00 KB / 67.31 MB [_________________________________] 0.14 % 68.36 KB/s 16m46s 
issues while extracting: 
 
is there anyone who can help me??

Best Regards
Pillar
LinkSprite Technologies, Inc.
Voice: 86-18971197460 （China）
skype: pillar_zuo / QQ:471044839
Website:www.pcduino.com
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