Demo server

The code running and updating the demo server is part of the main repository. This document describes how it can be used to run a Metashell demo server and how the code works.

Running a Metashell demo server


  • Ubuntu server 18.04. Note that it might work on other systems, but it is not tested.
  • At least 10 GB free space
  • A number of dependent packages (see the list of them in the installation instructions)


Before you install the demo, you need to decide which branch of Metashell to use for getting the server's code. Unless you'd like to test a specific branch, you should use master. These steps use this branch. If you'd like to use a different branch, you need to replace master with the name of your branch in the commands.

  • Download the installer: wget
  • Run the installer: METASHELL_BRANCH=master /bin/bash install
  • The above step will install Shell in a Box on your server if it was not installed already. Installing it will run it as well. If you don't need it, you can stop and disable it by running: sudo /etc/init.d/shellinabox stop and sudo update-rc.d shellinabox disable
  • Once the upgrader service has downloaded and deployed Metashell and the libraries that are available in the demo, it generates a website for Metashell and for launching the demo. This is generated in ${INSTALL_DIR}/share/metashell_${METASHELL_BRANCH}/html. You might want to install Apache on your server and make /var/www/html a symlink to this directory to make Apache serve the generated website:
  • sudo apt-get install apache2
  • sudo mv /var/www/html /var/www/html.backup
  • sudo ln -s ${INSTALL_DIR}/share/metashell_${METASHELL_BRANCH}/html /var/www/html

The installation script is configurable using environment variables. Here are the options and their default values:

  • METASHELL_BRANCH=master The branch to get the server's code (eg. updater script, wrapper for Metashell, etc) from.
  • INSTALL_DIR=/usr/local/share/metashell The directory to use for fetching and building Metashell and libraries provided by the demo.
  • SERVICE_USER=nobody The user to run the demo Metashell processes as.
  • SERVICE_GROUP=nogroup The group to use for the demo.
  • SERVICE_PORT=4202 The port ShellInABox will be listening on.
  • DELAY_SECS_BETWEEN_PULLS=3600 The delay the deployer script waits between the pulls (regardless of how long a pull & build takes)
  • SPLASH= Text to display in the splash message of the shell.

Uninstalling the Metashell demo server

Run the following command: wget -O- | /bin/bash

Note that if you installed the demo into a directory other than the default, you need to set the INSTALL_DIR environment variable here for the uninstaller script to remove that as well.

You can optionally remove the dependent packages from your server (you can find the list of them in the installation steps).

How the demo server works

The demo consists of two daemons on your server:

  • metashell_upgrader is responsible for upgrading Metashell from the main repository and the libraries provided by the demo.
  • metashell_demo is responsible for running ShellInABox for Metashell.

As they are deployed as two daemons, you can turn one or the other off.

The tools/demo_server/bin/deploy script takes a config file describing a number of repositories to clone, build and deploy. It deploys/updates the code. This script is executed regularly by the metashell_upgrader daemon.

Cloning repositories

The deploy script downloads the code from a number of repositories (specified by the config file). These repositories are cloned into INSTALL_DIR/src. Each repository is given an identifier (specified by the config file) and is cloned into a subdirectory with the same name. Under that directory, each branch of the remote repository has its own clone in a directory with the branch name.

For example if there is a Git repository with the following branches:

  • master
  • develop
  • some_feature

and the config file gives this repository the name some_lib, the following directories are created:

  • src/some_lib/master The repository is cloned here and the master branch is checked out.
  • src/some_lib/develop The repository is cloned here and the develop branch is checked out.
  • src/some_lib/some_feature The repository is cloned here and the some_feature branch is checked out.

Note that subsequent execution of the deploy script updates the checked-out code and deletes subdirectories when a branch gets deleted in the remote repository.

Deploying headers and binaries

After cloning the repositories, the deploy script builds the code (according to the build commands specified by the config file) and deploys the binaries and headers (specified by the config file).

Deploying the binaries

The binaries are deployed into INSTALL_DIR/bin. The files are suffixed with _<git commit hash> of the commit they are coming from. A symlink is created for each branch in the same directory pointing to the binary coming from the head of the branch. For example if a repository has a master branch and deploys the application binary, the script will create INSTALL_DIR/bin/application_<git commit hash> and INSTALL_DIR/bin/application_master pointing to application_<git commit hash>.

Note that old binaries not referred to by a branch are deleted.

Deploying the headers

The headers are deployed into INSTALL_DIR/include/<name of config>_<git commit hash>. A symlink is created for each branch similarly to the way it is done for binaries.

Deploying shared files

Shared files are deployed into INSTALL_DIR/share/<name of config>_<git commit hash>. A symlink is created for each branch similarly to the way it is done for binaries.

Generating the launcher page

The deployer can generate a HTML page users of the demo server can use to launch the demo from. The generation uses the Cheetah templating engine. You need to provide the template file and the location of the generated file (relative to the deployed share directory). You can use the following variables in the template:

  • $port This resolves to the port the demo uses. (It is specified by SERVICE_PORT during the installation of the demo)
  • $configs This resolves to the list of configs. Each config has the following fields:
  • name Name of the config (name field of the JSON document)
  • display_name Display name of the config
  • url Url of the config (url field of the JSON document)
  • versions List of deployed versions of the library.

The config file

The deploy script has a config file describing which projects to download and build. The config file is a JSON document (and the one used is located in tools/demo_server/config/metashell.json), which contains an array of config entries. Each entry describes on project to download and build. Each entry is an object with the following fields:

  • name: The name of the project. This is used the unique identifier of the project.
  • git: The source to clone the code from using Git.
  • build: (optional) The commands to build the downloaded code. The value of it is a list. Each entry is a list of strings describing one command. These commands are executed in the root of the cloned repository.
  • bin: (optional) The list of binaries to deploy. The value of it is a list of strings. Each string is a path (relative to the root of the cloned repository) of a file to deploy.
  • include: (optional) The list of headers to deploy. The value of it is a list of objects. Each object describes a file or directory to deploy.
  • share: (optional) The list of shared files to deploy. The value of it is a list of objects. Each object describes a file or directory to deploy.
  • url: (optional) The URL to the project page of the config.
  • launcher: (optional) Information about a launcher page generation for the config. The value of it is an object with two fields: src specifying the location of the template file (relative to the source root of the cloned config), dst specifying the location of the generated file (relative to the deployed share directory of the config).
  • default_version: (optional) The version to be selected by default on the generated configuration page.

Entries in the include and share list are objects with the following fields:

  • src: The path (relative to the root of the cloned repository) of the file or directory to deploy.
  • dst: (optional) The name of the deployed file or directory.
  • to_config: (optional) The name of a config object. When specified, the file or directory will be deployed as a file belonging to the specified project, not the one it is coming from.

The value of the src field can contain a * character. It is a wildcard for a path entry. Note that when it is used, it has to be an entire entry of the path (eg. include/*/boost is ok, include/1.*/boost is not). Also note that it matches hidden files.

When * is used in src, then all matches will be deployed. The values it matches will override the branch of the repository, the files are coming from. For example if include/*/boost is used and there is a directory called include/1.0/boost, then it will be deployed as if it was coming from the branch 1.0 of the repository referred to by the git element of the config.