(topic-installer-actions)= # What does the installer do? This document details what exactly the installer does to the machine it is run on. ## `apt` Packages installed The packages `python3` and `python3-venv` are installed from the apt repositories. ## Hub environment JupyterHub is run from a python3 virtual environment located in `/opt/tljh/hub`. It uses the system's installed python and is owned by root. It also contains a binary install of [traefik](http://traefik.io/). This virtual environment is completely managed by TLJH. :::{note} If you try to remove TLJH, revert this action using: ```bash sudo rm -rf /opt/tljh/hub ``` ::: ## User environment By default, a `mambaforge` conda environment is installed in `/opt/tljh/user`. This contains the notebook interface used to launch all users, and the various packages available to all users. The environment is owned by the `root` user. JupyterHub admins may use to `sudo -E conda install` or `sudo -E pip install` packages into this environment. This conda environment is added to `$PATH` for all users started with JupyterHub. If you are using `ssh` instead, you can activate this environment by running the following: ```bash source /opt/tljh/user/bin/activate ``` This should let you run various `conda` and `pip` commands. If you run into errors like `Command 'conda' not found`, try prefixing your command with: ```bash sudo env PATH=${PATH} ``` By default, `sudo` does not respect any custom environments you have activated. The `env PATH=${PATH}` 'fixes' that. :::{note} If you try to remove TLJH, revert this action using: ```bash sudo rm -rf /opt/tljh/user ``` ::: ## `tljh-config` symlink We create a symlink from `/usr/bin/tljh-config` to `/opt/tljh/hub/bin/tljh-config`, so users can run `sudo tljh-config ` from their terminal. While the user environment is added to users' `$PATH` when they launch through JupyterHub, the hub environment is not. This makes it hard to access the `tljh-config` command used to change most config parameters. Hence we symlink the `tljh-config` command to `/usr/bin`, so it is directly accessible with `sudo tljh-config `. :::{note} If you try to remove TLJH, revert this action using: ```bash sudo unlink /usr/bin/tljh-config ``` ::: ## `jupyterhub_config.d` directory for custom configuration snippets Any files in /opt/tljh/config/jupyterhub_config.d that end in .py and are a valid JupyterHub configuration will be loaded after any of the config options specified with tljh-config are loaded. :::{note} If you try to remove TLJH, revert this action using: ```bash sudo rm -rf /opt/tljh/config ``` ::: ## Systemd Units TLJH places 2 systemd units on your computer. They all start on system startup. 1. `jupyterhub.service` - starts the JupyterHub service. 2. `traefik.service` - starts traefik proxy that manages HTTPS In addition, each running Jupyter user gets their own systemd unit of the name `jupyter-`. :::{note} If you try to remove TLJH, revert this action using: ```bash # stop the services systemctl stop jupyterhub.service systemctl stop traefik.service systemctl stop jupyter- # disable the services systemctl disable jupyterhub.service systemctl disable traefik.service # run this command for all the Jupyter users systemctl disable jupyter- # remove the systemd unit rm /etc/systemd/system/jupyterhub.service rm /etc/systemd/system/traefik.service # reset the state of all units systemctl daemon-reload systemctl reset-failed ``` ::: ## State files TLJH places 3 `jupyterhub.service` and 4 `traefik.service` state files in `/opt/tljh/state`. These files save the state of JupyterHub and Traefik services and are meant to be used and modified solely by these services. :::{note} If you try to remove TLJH, revert this action using: ```bash sudo rm -rf /opt/tljh/state ``` ::: ## Progress page files If you ran the TLJH installer with the `--show-progress-page` flag, then two files have been added to your system to help serving the progress page: - `/var/run/index.html` - the main progress page - `/var/run/favicon.ico` - the JupyterHub icon :::{note} If you try to remove TLJH, revert this action using: ```bash sudo rm /var/run/index.html sudo rm /var/run/favicon.ico ``` ::: ## User groups TLJH creates two user groups when installed: 1. `jupyterhub-users` contains all users managed by this JupyterHub 2. `jupyterhub-admins` contains all users with admin rights managed by this JupyterHub. When a new JupyterHub user logs in, a unix user is created for them. The unix user is always added to the `jupyterhub-users` group. If the user is an admin, they are added to the `jupyterhub-admins` group whenever they start / stop their notebook server. If you uninstall TLJH, you should probably remove all user accounts associated with both these user groups, and then remove the groups themselves. You might have to archive or delete the home directories of these users under `/home/`. :::{note} If you try to remove TLJH, in order to remove a user and its home directory, use: ```bash sudo userdel -r ``` ::: Keep in mind that the files located in other parts of the file system will have to be searched for and deleted manually. :::{note} To remove the user groups units: ```bash sudo delgroup jupyterhub-users sudo delgroup jupyterhub-admins # remove jupyterhub-admins from the sudoers group sudo rm /etc/sudoers.d/jupyterhub-admins ``` ::: ## Passwordless `sudo` for JupyterHub admins `/etc/sudoers.d/jupyterhub-admins` is created to provide passwordless sudo for all JupyterHub admins. We also set it up to inherit `$PATH` with `sudo -E`, to more easily call `conda`, `pip`, etc. ## Removing TLJH If trying to wipe out a fresh TLJH installation, follow the instructions on how to revert each specific modification the TLJH installer does to the system. :::{note} If using a VM, the recommended way to remove TLJH is destroying the VM and start fresh. ::: :::{warning} Completely uninstalling TLJH after it has been used is a difficult task because it's highly coupled to how the system changed after it has been used and modified by the users. Thus, we cannot provide instructions on how to proceed in this case. :::