@dobey @doniks Ok,Thanks for offering these suggestions.
I decided to turn back to pi and setup a hdmi screen for it. Meanwhile try to run some scripts on UT flo. After all,with Java & Python & command line, there are lots of program can be run already.

I successfully installed the docker.ce using 'get.docker.io', as I got on the Raspbian Pi.

root@ubuntu-phablet:/# docker version
Client:
 Version:           18.09.4
 API version:       1.39
 Go version:        go1.10.8
 Git commit:        d14af54
 Built:             Wed Mar 27 18:44:30 2019
 OS/Arch:           linux/arm
 Experimental:      false
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

But I cannot lunch docker service.

root@ubuntu-phablet:/# service docker start
/usr/bin/env.fakechroot: 135: /usr/bin/env.fakechroot: /etc/init.d/docker: not found

Which might caused by the fakeroot, Is there any other ways to install docker.ce?

@dobey @doniks Ok,Thanks for offering these suggestions.
I decided to turn back to pi and setup a hdmi screen for it. Meanwhile try to run some scripts on UT flo. After all,with Java & Python & command line, there are lots of program can be run already.

@dobey @doniks @dobey
Well.First,I have to admit that I'm not a seasoned linux player.
I searched the keywords Ubuntu nexus7 and Google told me to try Ubuntu Torch.
I got one more question for UT:Is there anyways to install a UI apps like chromium on it and be able to browser pages as we usually do on Desktops. I successfully installed the chromium in the container and use a selenium to operate it. But don't know how to display the UI. I have to run it with --headless and --disable-gpu.
Then, as @dobey said run a traditional desktop Linux distro on the pad, I tried again and got the pages below.
1.https://wiki.ubuntu.com/Nexus7/Installation
This is what I want, but it seems that it is Nexus7-2012 not the flo. And the core version is a little bit old.
2.https://askubuntu.com/questions/879307/how-to-install-ubuntu-desktop-version-on-nexus-7-2013flo.
No reply.
To me , I just know both pi and flo have the arm architecture , and both of them can run linux desktop or Android system. I don't know why it's hard to find a desktop linux for flo. Which might lead to another question, what is the difference between the
arm ubuntu-desktop and ubuntu-torch , and why ubuntu-torch is more popular than ubuntu-desktop.
Any suggestions?Thanks for reply.
By the way, Do you know the su passwd on UT, which i failed to find in UT documents.

@jezek @dobey
OK.
Just things I want.
Make the Nexus 7 pad working as a Raspberry Pi with battery , touch pad and screen.
Which means:
1.Keep program running well no matter the hardware screen is closed, disconnected(locked) or not.
2.Get a ssh access directly to the root bash on the Ubport(or the container root bash) ,in which we can install whatever I what.
3.Install GUI desktop like Gnome or Kde , thus we can run UI apps like chromium or gedit.

@dobey
@jezek
That's true.
I tried apt install screen on ubport and apt can't run.
But when I try pip3 install somepackage on the Ubport, It goes right and the python package installed. Both of them will be successfully installed inside the container. Why is that? Does apt use a different space from pip on the Ubport ?

Is anyother way to meet the need?
For example:

1. Add a switch to turn off/on the screen backlight instead of locking the screen to keep the container running?

2. Add a tunnel so that the openssh server inside the container may be connect though a user-defined port other than port22 of the original Ubport. Like the Google Docker command docker run -d -p 127.0.0.1:5001:5000 training/webapp bash. Thus we can get an access like this: Desktop PC Terminal->port xx tunnel inside the container->container screen command or reconnect to a running screen.

3. Make a command like the Google Docker. Like ctrl+p+q to jump outside and keep container running and docker attach d48b21a7e439to reconnect to a running container.

Hi,there.
I just tried the Ubport on Nexus 7 2013 flo.
Thanks for the owe-some job, Now the Nexus turns out to be a little server in my pocket, with java and python.

I use ssh to access the main ubuntu (mount with rw) and then run the container with

libertine-container-manager exec -i CONTAINER-IDENTIFIER -c "COMMAND-LINE"

And get a root bash in the container.

Here is my problems:

1. When I start script via Destop ssh ->ubport->container->bash->python script.The script runs selenium and start chrome. It runs fine. Once I lock the Nexus screen.The program stoped, and python report errors. It seems that the container will stop running while locker. How can I keep the program running will locking the screen.

2. It seems that I cannot run apt install on the original ubuntu out side the container?Why is that?

E: You don't have enough free space in /var/cache/apt/archives/.

3. How can I keep program running and quit the ssh tunnel?Then reconnect to it, to seen what the program has returned?