1 - ROS2 - Démarrage

Installation PC ROS2

ROS est un Middleware Open Source pour développer des applications robotiques. Originellement développé sous Linux (Ubuntu), il est maintenant disponible sur plusieurs systèmes d'exploitation dont Debian et Windows.

Installation des prérequis et liens importants

Pour des raisons de stabilité et légèreté du système, il y a tout à penser que les déploiements de ROS dans des milieux industriels se font (robotique autonome et mobile) et se feront à l'avenir sur Ubuntu et de plus en plus Debian. L'industrie des serveurs a déjà largement adopté Debian pour sa stabilité et sa modularité. C'est pourquoi plutôt que d'apprendre la ligne de commande Windows, nous recommandons d'apprendre la ligne de commande Bash, utilisée dans Ubuntu/Debian. Pour cela, il faut installer un système (noyau) Linux, plusieurs options s'offrent à nous:

Notes importantes pour les installations virtuelles (deux premières options d'installation) :

Ubuntu via Windows SubSystem for Linux (WSL2)

WSL2 installe une machine virtuelle avec le noyau Linux complet, supporté et managé par Microsoft Windows. Il n'y a pas besoin de droits administrateur car le logiciel est disponible dans le store Windows.

Prérequis :

Installation de Ubuntu 22 :

sudo apt update
sudo apt upgrade

Depuis Windows, pour éteindre les Machines Virtuelles Ubuntu et ainsi libérer la mémoire RAM affectée :

Docker dans une VM WSL2

Pour utiliser docker dans une VM WSL2, par exemple Ubuntu :

Ubuntu via VirtualBox

Télécharger et installer VirtualBox pour Windows : https://www.oracle.com/virtualization/technologies/vm/downloads/virtualbox-downloads.html

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Exportation de VM au format OVF

Le système du TP est maintenu à jour et testé sur un PC Windows. Pour l'exporter sur les PC de salle TP, on veut avoir une image la plus petite possible.

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Setup pour TP MoveIt2+URSim à l'IUT de Haguenau

La première année j'ai expérimenté avec des PC Windows et VirtualBox :

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En 2025 je change donc de fusil d'épaule et utilise la salle réseau de l'IUT :

Migration VM vers disque physique

Entre 2024 et 2025 je suis passé de TPs en VM VirtualBox vers des PC physiques. Dans les deux cas, je maintiens l'environnement de TP sur VirtualBox de mon PC Windows. Ceci présente l'avantage de pouvoir maintenir des états de machines en fonction du type de TP.

On peut déployer un disque virtuel de VM vers un disque physique :

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Windows 10/11

Une installation native sous Windows 10 avec Visual Studio 2019 (Version Community gratuite) est possible :

Installation de ROS2 Humble

Les distributions stables publiées (pré-compilées) de ROS2 sont nommées par ordre alphabétique. Début 2023, on va installer ROS 2 Humble :

sudo apt update && sudo apt install locales
sudo locale-gen en_US en_US.UTF-8
sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8
export LANG=en_US.UTF-8
sudo apt install software-properties-common
sudo add-apt-repository universe
sudo apt update && sudo apt install curl
sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null
sudo apt update && sudo apt upgrade
sudo apt install ros-humble-desktop-full
source /opt/ros/humble/setup.bash
echo 'source /opt/ros/humble/setup.bash' >> ~/.bashrc

Tester l'installation

https://docs.ros.org/en/humble/Installation/Ubuntu-Install-Debians.html#try-some-examples

Installation de Jazzy pour la Navigation et Manipulation

avec UR, Turtlebot3, Nav2, MoveIt2, etc.

  1  sudo apt update && sudo apt install locales
    2  sudo locale-gen en_US en_US.UTF-8
    3  sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8
    4  export LANG=en_US.UTF-8
    5  sudo apt install software-properties-common
    6  sudo add-apt-repository universe
    7  sudo apt update && sudo apt install curl
    8  sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
    9  echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null
   10  sudo apt update && sudo apt upgrade
   11  sudo apt install ros-dev-tools
   12  exit
   13  locale
   14  sudo apt install ros-jazzy-desktop-full
   15  echo 'source /opt/ros/jazzy/setup.bash' >> ~/.bashrc
   16  exit
   17  ros2 run demo_nodes_cpp talker~
   18  ros2 run demo_nodes_cpp talker
   19  exit
   20  ros2 run demo_nodes_cpp listener
   21  exit
   22  sudo apt install docker-compose
   23  sudo usermod -aG docker $USER
   24  sudo service docker start
   25  docker run hello-world
   26  sudo service docker status
   27  docker run hello-world
   28  exit
   29  docker run hello-world
   30  sudo service docker restart
   31  docker run hello-world
   32  sudo usermod -aG docker robot
   33  docker run hello-world
   34  docker pull universalrobots/ursim_e-series
   35  exit
   36  docker run hello-world
   37  sudo service docker restart
   38  docker run hello-world
   39  sudo service docker start
   40  sudo service docker status
   41  docker run hello-world
   42  docker pull universalrobots/ursim_e-series
   43  sudo usermod -aG docker robot
   44  exit
   45  sudo apt install python3-argcomplete python3-colcon-common-extensions libboost-system-dev build-essential
   46  sudo apt install ros-jazzy-hls-lfcd-lds-driver ros-jazzy-turtlebot3-msgs ros-jazzy-dynamixel-sdk libudev-dev
   47  mkdir -p ~/turtlebot3_ws/src && cd ~/turtlebot3_ws/src
   48  git clone -b humble-devel https://github.com/ROBOTIS-GIT/turtlebot3.git
   49  git clone -b ros2-devel https://github.com/ROBOTIS-GIT/ld08_driver.git
   50  cd ~/turtlebot3_ws/src/turtlebot3
   51  rm -r turtlebot3_cartographer turtlebot3_navigation2
   52  cd ~/turtlebot3_ws/
   53  echo 'source /opt/ros/humble/setup.bash' >> ~/.bashrc
   54  source ~/.bashrc
   55  cd ..
   56  sudo nano .bashrc
   57  exit
   58  cd turtlebot3_ws/
   59  source install/setup.bash 
   60  ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py
   61  ls src/
   62  colcon build --symlink-install
   63  rosdep update && rosdep install --ignore-src --from-paths src -y
   64  vcs --help
   65  vcs status
   66  sudo apt list ros-jazzy-gazebo-ros-pkgs
   67  sudo apt list ros-jazzy-ros-gz
   68  sudo apt install ros-jazzy-ros-gz
   69  colcon build --symlink-install
   70  ros2 launch nav2_bringup tb3_simulation_launch.py slam:=True nav:=True headless:=False use_sim_time:=True
   71  sudo apt install ros-jazzy-navigation2 ros-jazzy-nav2-bringup 
   72  ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False
   73  exit
   74  cd ..
   75  cd turtlebot3_ws/
   76  colcon build --symlink-install --parallel-workers 1
   77  cd src/
   78  git clone -b humble https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git
   79  cd ..
   80  colcon build --symlink-install --parallel-workers 1
   81  sudo nano .bashrc
   82  sudo nano ~/.bashrc
   83  source install/setup.bash 
   84  ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py
   85  sudo apt list ros-jazzy-turtlebot3-*
   86  sudo apt install ros-jazzy-turtlebot3-fake-node
   87  sudo apt install ros-jazzy-gazebo-msgs
   88  cd src/
   89  sudo apt update && rosdep install -r --from-paths . --ignore-src --rosdistro $ROS_DISTRO -y
   90  rosdep update
   91  sudo apt update && rosdep install -r --from-paths . --ignore-src --rosdistro $ROS_DISTRO -y
   92  sudo curl https://packages.osrfoundation.org/gazebo.gpg --output /usr/share/keyrings/pkgs-osrf-archive-keyring.gpg
   93  echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/pkgs-osrf-archive-keyring.gpg] http://packages.osrfoundation.org/gazebo/ubuntu-stable $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/gazebo-stable.list > /dev/null
   94  sudo apt-get update
   95  sudo apt-get install gz-harmonic
   96  cd ..
   97  colcon build --symlink-install --parallel-workers 1
   98  cd ..
   99  ls
  100  mkdir -p ur_ws/src
  101  cd ur_ws/src
  102  cd ..
  103  git clone https://github.com/UniversalRobots/Universal_Robots_ROS2_Tutorials.git src/ur_tutorials
  104  rosdep update && rosdep install --ignore-src --from-paths src -y
  105  git clone -b ros2 https://github.com/UniversalRobots/Universal_Robots_ROS2_GZ_Simulation.git src/ur_simulation_gz
  106  rosdep update && rosdep install --ignore-src --from-paths src -y
  107  colcon build --symlink-install
  108  exit
  109  docker run hello-world
  110  docker pull universalrobots/ursim_e-series
  111  ros2 run ur_robot_driver start_ursim.sh -m ur5e
  112  sudo apt install ros-jazzy-ur
  113  sudo apt list python3-rosdep
  114  sudo rosdep init
  115  rosdep update
  116  sudo apt update
  117  sudo apt dist-upgrade
  118  ros2 run ur_robot_driver start_ursim.sh -m ur5e
  119  sudo apt list python3-colcon*
  120  colcon mixin add default https://raw.githubusercontent.com/colcon/colcon-mixin-repository/master/index.yaml
  121  colcon mixin update default
  122  sudo apt list python3-vcstool
  123  mkdir -p ~/ws_moveit/src
  124  cd ~/ws_moveit/src
  125  git clone -b main https://github.com/moveit/moveit2_tutorials
  126  vcs import --recursive < moveit2_tutorials/moveit2_tutorials.repos
  127  cd moveit2
  128  git checkout jazzy
  129  ls 
  130  ls moveit2.repos 
  131  cat moveit2.repos 
  132  cd ..
  133  cd src/
  134  sudo apt update && rosdep install -r --from-paths . --ignore-src --rosdistro $ROS_DISTRO -y
  135  cd ..
  136  colcon build --mixin releasee

Installation d'autres versions de ROS2

Pour avoir accès à toutes les dernières fonctionnalités en cours de développement (partiellement publiées), il faut installer ROS2 Rolling, qui est une distribution en développement continu "rolling release". Par exemple en Avril 2023, l'API Python de MoveIt2 et son tutoriel ne sont disponibles que sous rolling.

On peut installer plusieurs versions de ros en parallèle. Chaque version sera installée dans /opt/ros/version. Pour faire cohabiter les deux versions, il faut "sourcer" le bon répertoire avant de lancer un programme ros2 launch ... ou de compiler un workspace colcon build .... Deux options s'offrent à nous :

Gestion de version avec Ansible

L'idéal serait de gérer l'état des VM/PC de TP avec ansible plutôt que des snapshot VirtualBox

https://github.com/richlamdev/ansible-desktop-ubuntu

Outils utiles

Terminal multi-fenêtres Terminator

Visual Studio Codium

Pour éviter d'alourdir la VM avec de la télémétrie Microsoft, on installe la version sans tracker de Visual Studio Code depuis un dépôt debian :

wget https://gitlab.com/paulcarroty/vscodium-deb-rpm-repo/raw/master/pub.gpg 
sudo mv pub.gpg /usr/share/keyrings/vscodium-archive-keyring.asc
echo 'deb [ signed-by=/usr/share/keyrings/vscodium-archive-keyring.asc ] https://paulcarroty.gitlab.io/vscodium-deb-rpm-repo/debs vscodium main' \
    | sudo tee /etc/apt/sources.list.d/vscodium.list
sudo apt update
sudo apt install codium

Installer Firefox dans WSL

https://askubuntu.com/questions/1444962/how-do-i-install-firefox-in-wsl-when-it-requires-snap-but-snap-doesnt-work

sudo snap remove firefox
sudo apt remove firefox
sudo add-apt-repository ppa:mozillateam/ppa

# Create a new file, it should be empty as it opens:
sudo gedit /etc/apt/preferences.d/mozillateamppa

# Insert these lines, then save and exit
Package: firefox*
Pin: release o=LP-PPA-mozillateam
Pin-Priority: 501

# after saving, do
sudo apt update
sudo apt install firefox-esr

Alléger Ubuntu (pour VM ou clonage)

Désinstaller snap :

sudo rm -rf /var/cache/snapd/

sudo apt autoremove --purge snapd gnome-software-plugin-snap

rm -fr ~/snap

# sudo apt-mark hold snapd

cat <<EOF | sudo tee /etc/apt/preferences.d/nosnap.pref
# To prevent repository packages from triggering the installation of Snap,
# this file forbids snapd from being installed by APT.
# For more information: https://linuxmint-user-guide.readthedocs.io/en/latest/snap.html

Package: snapd
Pin: release a=*
Pin-Priority: -10
EOF

Installer le magasin d'applications de gnome sans snap/flatpak sudo apt install gnome-software --no-install-recommends

Supprimer les paquets apt plus nécessaires sudo apt autoremove --purge

Supprimer le cache de compilation de VSCode ~/.cache/vscode-cpptools

Supprimer les fichiers de compilation des workspaces qui ne seront pas utilisés en TP. Attention à conserver les paquets qui devront être compilés en TP (en utilisant colcon build --package-select).

Réduire la taille de la partition via l'application Disks. Celle-ci pourra être agrandie après copie de la VM.

Sources

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Auteur: Gauthier Hentz, sur le wiki de l'innovation de l'IUT de Haguenau

Attribution-NonCommercial-PartageMemeConditions 4.0 International (CC BY-NC-SA 4.0)

Tutoriels de base

Pour comprendre les concepts de ROS2 par la pratique, il existe des tutoriels pour débutant. Ils reposent sur la simulation d'un robot mobile à deux roues principales développé par les développeurs de ROS en 2010 : Turtlebot. Le TurtleBot 3 est vendue par Robotis et peut être couplé à un bras manipulateur 5 axes OpenMANIPULATOR-X. Il est possible de simuler des applications de manipulation mobile avec Gazebo.

Pour réaliser les tutoriels de base, il nous faut un environnement de développement, deux options :

Supposons que vous avez installé et testé votre environnement comme celui de la VM.

Connexion à la VM

Nous pouvons directement passer aux tutoriels sur les outils ROS 2 en ligne de commande :

Ces premiers tutoriels ne nécessitent qu'une installation basique de ROS 2, on n'y regarde pas le code source.

Ensuite on passe aux tutoriels sur les bibliothèques clientes de ROS 2 en C++ et Python : 

Ces tutoriels vous engagent à copier et analyser du code source en C++ et Python. Les fichiers créés sont placés dans le dossier de travail (workspace) /home/etudiant/ros2_ws/src, à ouvrir avec Visual Studio Code :

image.png

Vous trouverez des fichiers de correction commentés dans ros2_ws/src/cpp_pubsub/src/, en particulier :

Pour les tester il faut lancer :

cd ~/ros2_ws
colcon build --packages-select cpp_pubsub
source install/setup.bash
ros2 run cpp_pubsub talker

Le noeud se met à publier/parler :

[INFO] [minimal_publisher]: Publishing: "Hello World: 0"
[INFO] [minimal_publisher]: Publishing: "Hello World: 1"
[INFO] [minimal_publisher]: Publishing: "Hello World: 2"
[INFO] [minimal_publisher]: Publishing: "Hello World: 3"
[INFO] [minimal_publisher]: Publishing: "Hello World: 4"

Puis dans un second Terminal :

ros2 run cpp_pubsub listener

Le noeud se met à écouter :

[INFO] [minimal_subscriber]: I heard: "Hello World: 10"
[INFO] [minimal_subscriber]: I heard: "Hello World: 11"
[INFO] [minimal_subscriber]: I heard: "Hello World: 12"
[INFO] [minimal_subscriber]: I heard: "Hello World: 13"
[INFO] [minimal_subscriber]: I heard: "Hello World: 14"

Tapez Ctrl+C dans chaque Terminal pour arrêter les noeuds ("stop spinning").

-----

Auteur: Gauthier Hentz, sur le wiki de l'innovation de l'IUT de Haguenau

 Attribution-NonCommercial-PartageMemeConditions 4.0 International (CC BY-NC-SA 4.0) 

Découverte d'Ubuntu Linux et son Terminal Bash

Navigating the Ubuntu GUI

In this exercise, we will familiarize ourselves with the graphical user interface (GUI) of the Ubuntu operating system.

Task 1: Familiarize Yourself with the Ubuntu Desktop

At the log-in screen, click in the password input box, enter rosindustrial for the password, and hit enter. The screen should look like the image below when you log in:

../../_images/ubuntu_desktop.png

There are several things you will notice on the desktop:

../../_images/ubuntu_desktop_details.png

  1. The gear icon on the top right of the screen brings up a menu which allows the user to log out, shut down the computer, access system settings, etc…

  2. The bar on the left side shows running and “favorite” applications, connected thumb drives, etc.

  3. The top icon is used to access all applications and files. We will look at this in more detail later.

  4. The next icons are either applications which are currently running or have been “pinned” (again, more on pinning later)

  5. Any removable drives, like thumb drives, are found after the application icons.

  6. If the launcher bar gets “too full”, clicking and dragging up/down allows you to see the applications that are hidden.

  7. To reorganize the icons on the launcher, click and hold the icon until it “pops out”, then move it to the desired location.


Task 2: Open and Inspect an Application

Click on the filing-cabinet icon in the launcher. A window should show up, and your desktop should look like something below:

../../_images/ubuntu_folder_browser.png

Things to notice:

  1. The close, minimize, and maximize buttons typically found on the right-hand side of the window title bar are found on the left-hand side.

  2. The menu for windows are found on the menu bar at the top of the screen, much in the same way Macs do. The menus, however, only show up when you hover the mouse over the menu bar.

  3. Notice that there are menu highlights of the folder icon. The dots on the left show how many windows of this application are open. Clicking on these icons when the applications are open does one of two things:

  • If there is only one window open, this window gets focus.

  • If more than one are open, clicking a second time causes all of the windows to show up in the foreground, so that you can choose which window to go to (see below):

../../_images/ubuntu_inspect.png


Task 3: Start an Application & Pin it to the Launcher Bar

Click on the launcher button (top left) and type gedit in the search box. The “Text Editor” application (this is actually gedit) should show up (see below):

../../_images/ubuntu_start_application.png

Click on the application. The text editor window should show up on the screen, and the text editor icon should show up on the launcher bar on the left-hand side (see below):

../../_images/ubuntu_application_pin.png

  1. Right-click on the text editor launch icon, and select “Lock to Launcher”.

  2. Close the gedit window. The launcher icon should remain after the window closes.

  3. Click on the gedit launcher icon. You should see a new gedit window appear.

Le Terminal Linux

In this exercise, we will familiarize ourselves with the Linux terminal.

Starting the Terminal

  1. Pour ouvrir le Terminal, recherchez le programme "terminator" ou cliquez sur l'icône:

    63008829.png

  2. Create a second terminal window, either by:

    • Right-clicking on the terminal and selecting the “Open Terminal” or

    • Selecting “Open Terminal” from the “File” menu

  3. Create a second terminal within the same window by pressing “Ctrl+Shift+T” while the terminal window is selected.

  4. Close the 2nd terminal tab, either by:

    • clicking the small ‘x’ in the terminal tab (not the main terminal window)

    • typing exit and hitting enter.

  5. The window will have a single line, which looks like this:

    ros-industrial@ros-i-humble-vm:~$

  6. This is called the prompt, where you enter commands. The prompt, by default, provides three pieces of information:

    1. ros-industrial is the login name of the user you are running as.

    2. ros-i-humble-vm is the host name of the computer.

    3. ~ is the directory in which the terminal is currently in. (More on this later).

  7. Close the terminal window by typing exit or clicking on the red ‘x’ in the window’s titlebar.

Navigating Directories and Listing Files

Prepare your environment

  1. Open your home folder in the file browser.

  2. Double-click on the ex0.3 folder we created in the previous step.

    • We’ll use this to illustrate various file operations in the terminal.

  3. Right click in the main file-browser window and select “Open in Terminal” to create a terminal window at that location.

  4. In the terminal window, type the following command to create some sample files that we can study later:

    • cp -a ~/industrial_training/exercises/0.3/. .

ls Command

  1. Enter ls into the terminal.

    • You should see test.txt, and new listed. (If you don’t see ‘new’, go back and complete the previous exercise).

    • Directories, like new, are colored in blue.

    • The file sample_job is in green; this indicates it has its “execute” bit set, which means it can be executed as a command.

  2. Type ls *.txt. Only the file test.txt will be displayed.

  3. Enter ls -l into the terminal.

    • Adding the -l option shows one entry per line, with additional information about each entry in the directory.

    • The first 10 characters indicate the file type and permissions

    • The first character is d if the entry is a directory.

    • The next 9 characters are the permissions bits for the file

    • The third and fourth fields are the owning user and group, respectively.

    • The second-to-last field is the time the file was last modified.

    • If the file is a symbolic link, the link’s target file is listed after the link’s file name.

  4. Enter ls -a in the terminal.

    • You will now see one additional file, which is hidden.

  5. Enter ls -a -l (or ls -al) in the command.

    • You’ll now see that the file hidden_link.txt points to .hidden_text_file.txt.

pwd and cd Commands

  1. Enter pwd into the terminal.

    • This will show you the full path of the directory you are working in.

  2. Enter cd new into the terminal.

    • The prompt should change to ros-industrial@ros-i-humble-vm:~/ex0.3/new$.

    • Typing pwd will show you now in the directory /home/ros-industrial/ex0.3/new.

  3. Enter cd .. into the terminal. * In the previous exercise, we noted that .. is the parent folder. * The prompt should therefore indicate that the current working directory is /home/ros-industrial/ex0.3.

  4. Enter cd /bin, followed by ls.

    • This folder contains a list of the most basic Linux commands.
      Note that pwd and ls are both in this folder.

  5. Enter cd ~/ex0.3 to return to our working directory.

    • Linux uses the ~ character as a shorthand representation for your home directory.

    • It’s a convenient way to reference files and paths in command-line commands.

    • You’ll be typing it a lot in this class… remember it!

If you want a full list of options available for any of the commands given in this section, type man <command> (where <command> is the command you want information on) in the command line. This will provide you with built-in documentation for the command. Use the arrow and page up/down keys to scroll, and q to exit.

Altering Files

mv Command

  1. Type mv test.txt test2.txt, followed by ls.

    • You will notice that the file has been renamed to test2.txt.
      This step shows how mv can rename files.

  2. Type mv test2.txt new, then ls.

    • The file will no longer be present in the folder.

  3. Type cd new, then ls.

    • You will see test2.txt in the folder.
      These steps show how mv can move files.

  4. Type mv test2.txt ../test.txt, then ls.

    • test2.txt will no longer be there.

  5. Type cd .., then ls.

    • You will notice that test.txt is present again.
      This shows how mv can move and rename files in one step.

cp Command

  1. Type cp test.txt new/test2.txt, then ls new.

    • You will see test2.txt is now in the new folder.

  2. Type cp test.txt "test copy.txt", then ls -l.

    • You will see that test.txt has been copied to test copy.txt.
      Note that the quotation marks are necessary when spaces or other special characters are included in the file name.

rm Command

  1. Type rm "test copy.txt", then ls -l.

    • You will notice that test copy.txt is no longer there.

mkdir Command

  1. Type mkdir new2, then ls.

    • You will see there is a new folder new2.

touch Command

  1. Type touch ~/Templates/"Untitled Document".

    • This will create a new Document named “Untitled Document”

You can use the -i flag with cp, mv, and rm commands to prompt you when a file will be overwritten or removed.

Editing Text (and Other GUI Commands)

  1. Type gedit test.txt.

    • You will notice that a new text editor window will open, and test.txt will be loaded.

    • The terminal will not come back with a prompt until the window is closed.

  2. There are two ways around this limitation. Try both…

  3. Starting the program and immediately returning a prompt:

    1. Type gedit test.txt &.

      • The & character tells the terminal to run this command in “the background”, meaning the prompt will return immediately.

    2. Close the window, then type ls.

      • In addition to showing the files, the terminal will notify you that gedit has finished.

  4. Moving an already running program into the background:

    1. Type gedit test.txt.

      • The window should open, and the terminal should not have a prompt waiting.

    2. In the terminal window, press Ctrl+Z.

      • The terminal will indicate that gedit has stopped, and a prompt will appear.

    3. Try to use the gedit window.

      • Because it is paused, the window will not run.

    4. Type bg in the terminal.

      • The gedit window can now run.

    5. Close the gedit window, and type ls in the terminal window.

      • As before, the terminal window will indicate that gedit is finished.

Running Commands as Root

  1. In a terminal, type ls -a /root.

    • The terminal will indicate that you cannot read the folder /root.

    • Many times you will need to run a command that cannot be done as an ordinary user, and must be done as the “super user”

  2. To run the previous command as root, add sudo to the beginning of the command.

    • In this instance, type sudo ls -a /root instead.

    • The terminal will request your password (in this case, rosindustrial) in order to proceed.

    • Once you enter the password, you should see the contents of the /root directory.

Warning: sudo is a powerful tool which doesn’t provide any sanity checks on what you ask it to do, so be VERY careful in using it

 

https://industrial-training-master.readthedocs.io/en/humble/_source/prerequisites/Navigating-the-Ubuntu-GUI.html

Usage avancé du bash Linux

Job management

Stopping Jobs

  1. Type ./sample_job.

    • The program will start running.

  2. Press Control+C.

    • The program should exit.

  3. Type ./sample_job sigterm.

    • The program will start running.

  4. Press Control+C.

    • This time the program will not die.

Stopping “Out of Control” Jobs

  1. Open a new terminal window.

  2. Type ps ax.

  3. Scroll up until you find python ./sample_job sigterm.

    • This is the job that is running in the first window.

    • The first field in the table is the ID of the process (use man ps to learn more about the other fields).

  4. Type ps ax | grep sample.

    • You will notice that only a few lines are returned.

    • This is useful if you want to find a particular process

    • Note: this is an advanced technique called “piping”, where the output of one program is passed into the input of the next. This is beyond the scope of this class, but is useful to learn if you intend to use the terminal extensively.

  5. Type kill <id>, where <id> is the job number you found with the ps ax.

  6. In the first window, type ./sample_job sigterm sigkill.

    • The program will start running.

  7. In the second window, type ps ax | grep sample to get the id of the process.

  8. Type kill <id>.

    • This time, the process will not die.

  9. Type kill -SIGKILL <id>.

    • This time the process will exit.

Showing Process and Memory usage

  1. In a terminal, type top.

    • A table will be shown, updated once per second, showing all of the processes on the system, as well as the overall CPU and memory usage.

  2. Press the Shift+P key.

    • This will sort processes by CPU utilization.
      This can be used to determine which processes are using too much CPU time.

  3. Press the Shift+M key.

    • This will sort processes by memory utilization
      This can be used to determine which processes are using too much memory.

  4. Press q or Ctrl+C to exit the program.