Merge pull request #221 from yuvipanda/ubuntu-version

Provide better error message when running on unsupported distro

.circleci/config.yml

@@ -57,7 +57,7 @@ jobs:
             - run:
                 name: setup python3
                 command: |
-                    apk add --no-cache python3
+                    apk add --no-cache python3 pytest
 
             - checkout
             - setup_remote_docker
@@ -79,6 +79,12 @@ jobs:
                         --installer-args "--plugin /srv/src/integration-tests/plugins/simplest" \
                         plugins test_simplest_plugin.py
 
+            - run:
+                name: Run bootstrap checks
+                command: |
+                    py.test integration-tests/test_bootstrap.py
+
+
 
     documentation:
         docker:

bootstrap/bootstrap.py

@@ -8,7 +8,8 @@ This script is run as:
     curl <script-url> | sudo python3 -
 
 Constraints:
-  - Be compatible with Python 3.4 (since we support Ubuntu 16.04)
+  - Entire script should be compatible with Python 3.6 (We run on Ubuntu 18.04+)
+  - Script should parse in Python 3.4 (since we exit with useful error message on Ubuntu 14.04+)
   - Use stdlib modules only
 """
 import os
@@ -17,8 +18,31 @@ import sys
 import logging
 
 
+def get_os_release_variable(key):
+    """
+    Return value for key from /etc/os-release
+
+    /etc/os-release is a bash file, so should use bash to parse it.
+
+    Returns empty string if key is not found.
+    """
+    return subprocess.check_output([
+        '/bin/bash', '-c',
+        "source /etc/os-release && echo ${{{key}}}".format(key=key)
+    ]).decode().strip()
 
 def main():
+
+    # Support only Ubuntu 18.04+
+    distro = get_os_release_variable('ID')
+    version = float(get_os_release_variable('VERSION_ID'))
+    if distro != 'ubuntu':
+        print('The Littlest JupyterHub currently supports Ubuntu Linux only')
+        sys.exit(1)
+    elif float(version) < 18.04:
+        print('The Littlest JupyterHub requires Ubuntu 18.04 or higher')
+        sys.exit(1)
+
     install_prefix = os.environ.get('TLJH_INSTALL_PREFIX', '/opt/tljh')
     hub_prefix = os.path.join(install_prefix, 'hub')
 

docs/index.rst

@@ -6,6 +6,7 @@ A simple `JupyterHub <https://github.com/jupyterhub/jupyterhub>`_ distribution f
 a small (0-100) number of users on a single server. We recommend reading
 :ref:`topic/whentouse` to determine if this is the right tool for you.
 
+
 Development Status
 ==================
 
@@ -18,7 +19,8 @@ Installation
 ============
 
 The Littlest JupyterHub (TLJH) can run on any server that is running at least
-Ubuntu 18.04. We have a bunch of tutorials to get you started.
+**Ubuntu 18.04**. Earlier versions of Ubuntu are not supported.
+We have a bunch of tutorials to get you started.
 
 - Tutorials to create a new server from scratch on a cloud provider & run TLJH
   on it. These are **recommended** if you do not have much experience setting up

integration-tests/conftest.py

@@ -4,12 +4,14 @@ import os
 
 from pytest import fixture
 
-from tljh.config import CONFIG_FILE, reload_component
 
 
 @fixture
 def preserve_config(request):
     """Fixture to save and restore config around tests"""
+    # Import TLJH only when needed. This lets us run tests in places
+    # where TLJH is not installed - particularly, the 'distro check' test.
+    from tljh.config import CONFIG_FILE, reload_component
     if os.path.exists(CONFIG_FILE):
         with open(CONFIG_FILE) as f:
             save_config = f.read()

integration-tests/test_bootstrap.py

@@ -0,0 +1,44 @@
+"""
+Test running bootstrap script in different circumstances
+"""
+import subprocess
+
+
+def test_ubuntu_too_old():
+    """
+    Error with a useful message when running in older Ubuntu
+    """
+    container_name = 'old-distro-test'
+
+    # stop container if it is already running
+    subprocess.run([
+        'docker', 'rm', '-f', container_name
+    ])
+    
+    # Start a detached Ubuntu 16.04 container
+    subprocess.check_call([
+        'docker', 'run', '--detach', '--name', container_name, 'ubuntu:16.04', 
+        '/bin/bash', '-c', 'sleep 1000s'
+    ])
+    # Install python3 inside the ubuntu container
+    # There is no trusted Ubuntu+Python3 container we can use
+    subprocess.check_output([
+        'docker', 'exec', container_name, 'apt-get', 'update'
+    ])
+    subprocess.check_output([
+        'docker', 'exec', container_name, 'apt-get', 'install', '--yes', 'python3'
+    ])
+    # Copy only the bootstrap script  to container, so this is faster
+    subprocess.check_call([
+        'docker',
+        'cp',
+        'bootstrap/', f'{container_name}:/srv'
+    ])
+
+    # Run bootstrap script, validate that it fails appropriately
+    output = subprocess.run([
+        'docker', 'exec', '-i', container_name,
+        'python3', '/srv/bootstrap/bootstrap.py'
+    ], check=False, stdout=subprocess.PIPE, encoding='utf-8')
+    assert output.stdout == 'The Littlest JupyterHub requires Ubuntu 18.04 or higher\n'
+    assert output.returncode == 1