[Ubuntu] 3G Modem (ZTE MF651) connection using command line

It started with "could not write bytes broken pipe"

after googling it, I found that the xserver package is missing. So, I need to reinstall the package(s) using command line. 

The problem is, my Ubuntu Computer's internet-connection only through 3G Modem (ZTE MF651). It's not automatically connected to internet. another googling.. and I found that I need to use:

$ nmcli con up id <id>

to get the id, I used:

$ nmcli con list

the NAME is the <id>. to type the id with space in it, use " ".

after the connection is up, I had to activated the DHCP client, using:

$ sudo dhclient usb0

It's a bug of Network Manager for this type of 3G Modem (reference).

then it's connected.

installed the package(s) and reboot.

DONE.