The teacher can use Epoptes to share (broadcast) his screen with the students, or to watch what they are doing and help them (monitor and assist): http://www.epoptes.org/screenshots

The username of the teacher should be added to the group epoptes in order to be able to use it: adduser username epoptes . Or you can create another admin user, which automatically is added to this group:

cd ltsp-server/
vagrant ssh
sudo su
cd /host/scripts/
./create-admin-account.sh username password

The script scripts/users.sh can be used to create, export, import, backup and restore user accounts. Try it like this:

cd ltsp-server/
vagrant ssh
sudo su
cd /host/
script/users.sh --help
script/users.sh create user-list.txt
script/users.sh backup
script/users.sh restore backup/users-20190113.tgz

This is useful when you need to create lots of accounts. Also, when you need to rebuild the virtual LTSP server, you can backup user accounts before doing it and restore them afterwards.

Usually you list the packages that should be installed on the client on the variable PACKAGES on settings.sh:

# List of extra packages that need to be installed on the client.
# For example: ubuntu-edu-preschool, ubuntu-edu-primary, etc.
PACKAGES="
  vim
  geany
  xfce4-terminal
"

However, often you need to install more packages (or to remove some) after the server has been built. In this case you have to make these customizations on the chroot directory and then rebuild the client image:

cd ltsp-server/
vagrant ssh

sudo su
rm /opt/ltsp/i386/etc/resolv.conf
ltsp-chroot -mr

apt update
apt upgrade
apt install emacs
exit    # from chroot

ltsp-update-image
systemctl restart nbd-server

On settings.sh there are these variables:

# If GUEST_ACCOUNTS is "yes" then guest accounts are created and
# a "Login as Guest" button is provided on the clients. Everything
# on a guest account will be reset on login.
#
# If GUEST_AUTOLOGIN is "yes", then the client will automatically
# login to a guest account as soon as it boots.
#
# The account GUEST_USER is used as a template (skeleton) for the
# guest accounts. You can login to this account in order to customize
# and tweak all the guest accounts.
GUEST_ACCOUNTS="yes"
GUEST_AUTOLOGIN="no"
GUEST_USER="guest"
GUEST_PASS="pass1"

If you login to and customize the account of GUEST_USER (for example change the background), this will be applied to all the guest logins.

You can easily increase or decrease the RAM of the VirtualBox LSP server like this:

• Stop the server with: ./server.sh halt (or cd ltsp-server/ ; vagrant halt)
• Edit settings.sh and change VB_RAM
• Start the server with: ./server.sh up (or cd ltsp-server/ ; vagrant up)

The same also works for changing LAN_IF (the network interface that is connected to the LAN). However for changing the other settings you need to rebuild the server (with ./server.sh build). If you want to preserve the user accounts, make sure to backup them first, and restore them after the rebuild.

Any user that has an account on the server can access the desktop of the server from a web browser. He can do it like this:

• Open https://12.34.56.78/guac/ on the browser. Here 12.34.56.78 is the IP of the server, most probably something like 192.168.0.xy, or 10.42.0.1 if you started a hotspot from the laptop.
• Click on the button "Login" without a username and password.
• Click on the RDP connection.
• Give the username and password of the account.

Note: I have noticed that sometimes the firewall has a glitch, especially when a hotspot is started, which prevents the server from being accessed from the clients. When this happens, I try ufw disable and then ufw enable, and the problem goes away somehow.

This is useful when the teacher wants to demonstrate to the students how to do something, for example how to write a program. Usually a projector is used to show the desktop of the teacher, but this is a nice alternative too, especially when there is no projector available.

To be able to share the screen of his account, the teacher should enter in Guacamole with the username student or admin (and the corresponding password). This is different from the case above, where he could login in Guacamole even without a username and password.

Then he should go to his account by clicking on the RDP connection and giving the username and password of his account. Afterwards he should follow these steps:

• Press Ctrl+Alt+Shift to open the Guacamole panel on the left side.
• Click on the "Share" menu of the top and then on "Watch".
• Right-click on the link that is displayed and copy it.
• Open https://12.34.56.78/chat/ (or https://10.42.0.1/chat/) and post the link there to share it with the students.

Once the students open in browser the link of the shared Guacamole session they will be able to see the desktop of the teacher and what he is doing.

The students can share their desktop too with the teacher and with other students. This is useful when a student is stuck and needs some help (for example he cannot find a bug in the program) or when the students are working in pairs or in groups.

To be able to share his desktop a student should login in Guacamole with the username student. Then he should follow the same steps as above, except that he should select "Collaborate" from the menu of "Share", instead of "Watch". The difference is that with "Collaborate" both parties (or all of them) can use the keyboard and mouse to work together, instead of just watching what the other person does.

Again they can use the chat (https://10.42.0.1/chat/) to share the link of the guacamole session with the others.

Instructions for installing Docker on Ubuntu are here: https://docs.docker.com/install/linux/docker-ce/ubuntu/

• Add the docker repository on the list of package repositories:

  apt update
  apt install \
      apt-transport-https \
      ca-certificates \
      curl \
      software-properties-common
  
  curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
  
  add-apt-repository \
     "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
     $(lsb_release -cs) \
     stable"
  

• Install the package docker-ce:

  apt update
  apt install docker-ce
  

• Verify that Docker CE is installed correctly by running the hello-world image:

  docker container run hello-world
  

DockerScripts is a shell script framework for Docker. It facilitates creating and maintaining docker containers.

Use these commands to install it:

apt install m4
git clone https://github.com/docker-scripts/ds /opt/docker-scripts/ds
cd /opt/docker-scripts/ds/
make install
ds
ds -h

We need wsproxy in order to get and maintain the free letsencrypt SSL certificates. It can be installed like this:

• Get its code: ds pull wsproxy
• Init a container directory for it: ds init wsproxy @wsproxy
• Customize the settings: cd /var/ds/wsproxy/; vim settings.sh
• Build image, create the container and configure it: ds make

• Get its code: ds pull desktop
• Init a container directory for it: ds init desktop @desktop.example.org
• Customize the settings: cd /var/ds/desktop.example.org/; vim settings.sh
• Build image, create the container and configure it: ds make

You can go inside the docker container and install other packages with apt, like this:

cd /var/ds/desk.example.org/
ds shell
apt install ubuntu-edu-preschool ubuntu-edu-primary firefox
exit

However in case you rebuild the server you will have to install them again manually. To install them automatically on each rebuild of the server, create a file like /var/ds/desk.example.org/packages with a content like this:

RUN DEBIAN_FRONTEND=noninteractive \
    apt install --yes \
        ubuntu-edu-preschool \
        ubuntu-edu-primary \
        firefox

The script users.sh can be used to create, export, import, backup and restore user accounts. Try it like this:

cd /var/ds/desk.example.org/
ds shell

/app-scripts/users.sh --help
/app-scripts/users.sh create user-list.txt
/app-scripts/users.sh backup
/app-scripts/users.sh restore backup/users-20190113.tgz

Before rebuilding the server you should make first a backup of the user accounts and homes, and after rebuilding it you should restore them:

cd /var/ds/desk.example.org/

ds shell
/app-scripts/users.sh backup
exit

ds make

ds shell
/app-scripts/users.sh restore backup/users-20190113.tgz
exit

Any user that has an account on the server can access the desktop of the server from a web browser. He can do it like this:

• Open https://desk.example.org:444/guac/ on the browser. Here the port 444 is the one that is forwarded to port 443 on settings.sh
• Click on the button "Login" without a username and password.
• Click on the RDP connection.
• Give the username and password of the account.

This is useful when the teacher wants to demonstrate to the students how to do something, for example how to write a program.

To be able to share the screen of his account, the teacher should enter in Guacamole with the username student or admin (and the corresponding password).

Then he should go to his account by clicking on the RDP connection and giving the username and password of his account. Afterwards he should follow these steps:

• Press Ctrl+Alt+Shift to open the Guacamole panel on the left side.
• Click on the "Share" menu of the top and then on "Watch".
• Right-click on the link that is displayed and copy it.
• Send the link to the students by email, instant message (chat), etc.

Once the students open in browser the link of the shared Guacamole session, they will be able to see the desktop of the teacher and what he is doing.

The students can share their desktop too with the teacher and with other students. This is useful when a student is stuck and needs some help (for example he cannot find a bug in the program) or when the students are working in pairs or in groups.

To be able to share his desktop a student should login in Guacamole with the username student. Then he should follow the same steps as above, except that he should select "Collaborate" from the menu of "Share", instead of "Watch". The difference is that with "Collaborate" both parties (or all of them) can use the keyboard and mouse to work together, instead of just watching what the other person does.

Then they can use email or chat to share the link of the guacamole session with the others.