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Installing Cassandra
--------------------

Prerequisites
^^^^^^^^^^^^^

- The latest version of Java 8, either the `Oracle Java Standard Edition 8
  <http://www.oracle.com/technetwork/java/javase/downloads/index.html>`__ or `OpenJDK 8 <http://openjdk.java.net/>`__. To
  verify that you have the correct version of java installed, type ``java -version``.

- For using cqlsh, the latest version of `Python 2.7 <https://www.python.org/downloads/>`__. To verify that you have
  the correct version of Python installed, type ``python --version``.

Installation from binary tarball files
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Download the latest stable release from the `Apache Cassandra downloads website <http://cassandra.apache.org/download/>`__.

- Untar the file somewhere, for example:

::

    tar -xzvf apache-cassandra-3.6-bin.tar.gz

The files will be extracted into ``apache-cassandra-3.6``, you need to substitute 3.6 with the release number that you
have downloaded.

- Optionally add ``apache-cassandra-3.6\bin`` to your path.
- Start Cassandra in the foreground by invoking ``bin/cassandra -f`` from the command line. Press "Control-C" to stop
  Cassandra. Start Cassandra in the background by invoking ``bin/cassandra`` from the command line. Invoke ``kill pid``
  or ``pkill -f CassandraDaemon`` to stop Cassandra, where pid is the Cassandra process id, which you can find for
  example by invoking ``pgrep -f CassandraDaemon``.
- Verify that Cassandra is running by invoking ``bin/nodetool status`` from the command line.
- Configuration files are located in the ``conf`` sub-directory.
- Since Cassandra 2.1, log and data directories are located in the ``logs`` and ``data`` sub-directories respectively.
  Older versions defaulted to ``/var/log/cassandra`` and ``/var/lib/cassandra``. Due to this, it is necessary to either
  start Cassandra with root privileges or change ``conf/cassandra.yaml`` to use directories owned by the current user,
  as explained below in the section on changing the location of directories.

Installation from Debian packages
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Add the Apache repository of Cassandra to ``/etc/apt/sources.list.d/cassandra.sources.list``, for example for version
  3.6:

::

    echo "deb http://www.apache.org/dist/cassandra/debian 36x main" | sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list

- Add the Apache Cassandra repository keys:

::

    curl https://www.apache.org/dist/cassandra/KEYS | sudo apt-key add -

- Update the repositories:

::

    sudo apt-get update

- If you encounter this error:

::

    GPG error: http://www.apache.org 36x InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A278B781FE4B2BDA

Then add the public key A278B781FE4B2BDA as follows:

::

    sudo apt-key adv --keyserver pool.sks-keyservers.net --recv-key A278B781FE4B2BDA

and repeat ``sudo apt-get update``. The actual key may be different, you get it from the error message itself. For a
full list of Apache contributors public keys, you can refer to `this link <https://www.apache.org/dist/cassandra/KEYS>`__.

- Install Cassandra:

::

    sudo apt-get install cassandra

- You can start Cassandra with ``sudo service cassandra start`` and stop it with ``sudo service cassandra stop``.
  However, normally the service will start automatically. For this reason be sure to stop it if you need to make any
  configuration changes.
- Verify that Cassandra is running by invoking ``nodetool status`` from the command line.
- The default location of configuration files is ``/etc/cassandra``.
- The default location of log and data directories is ``/var/log/cassandra/`` and ``/var/lib/cassandra``.