Linux 102 Class

This class is intended as a follow-on to the Code Academy command line course.

Flay's draft slides are here.

Infrastructure Components

This class runs on a multiuser VM. The management account on the VM runs a browser-based SSH server so that users can log into the VM without any tools besides a web browser, and a registration application that allows class participants to generate their own SSH accounts.

The browser-based SSH server uses WebSSH.

The registration application is a small Flask webapp. The CSS for the registration application is based on styles from this site.

One-time setup

Create the Linux class user group

Accounts for class participants are created in a group called linux_class to simplify tracking and management. To create the group, run:

sudo adduser --group linux_class

Set up the virtual environment

The SSH and registration applications are written to work with the latest version of Python. Pyenv makes it easy to use your Python version of choice and create independent virtual environments.

Once pyenv and pyenv-virtualenv are installed, run:

pyenv install 3.7.2
pyenv virtualenv 3.7.2 class
pyenv activate class
pip install --upgrade pip
cd ~/linux_class
pip install -r requirements.txt

Every time you run the class

The registration app runs on port 5000. The Web SSH app runs on port 8000.

Connect the VM to the network

• Start the Ubuntu server with a bridged network connection so it appears as another computer on the network.
• Log into the mplough account.
• Get the IP address of the machine.

Run the registration app

It's not possible to run adduser as not root, even if it's suid. So we have to run the registration app like this:

cd ~/linux_class/registration_app
sudo -s
pyenv activate class
export FLASK_APP=registration_app.py
/home/mplough/.pyenv/shims/flask run --host 0.0.0.0 -p 5000

I don't like this solution as it involves running a flask app as root, but it's expedient and the risk is acceptable given the isolated and snapshotted nature of the VM.

Run the Web SSH server

• Navigate to /home/mplough/linux_class directory and run:

wssh --port=8000

Manual setup

Add users

From /home/mplough/linux_class/survey_app,

sudo adduser --conf ./adduser.conf --ingroup linux_class [username]

Remove users

Nuke a user plus their home directory and files like so:

sudo userdel -r user

Skeleton directory

The adduser.conf file in the survey_app folder directs adduser to create a user with a home directory populated by the skeleton in the skel folder in this folder.

Note that the adduser.conf file includes an absolute path. I haven't tested it with relative paths, so you'll either need to change the absolute path to fit or you can test relative paths.