Remove Salt states
==================

.. note::

   This page describes a "meta" practice, in terms of maintaining the repository as a whole.

We try to remove unneeded services and packages from this repository, because carrying old configurations forever into the future increases the maintenance burden of this repository. If you don't know whether a package is still required, you can :ref:`inspect the package<inspect-package>`.

The ``./manage.py`` command has ``services`` and ``packages`` sub-commands to identify unusual services and packages, and an ``autoremove`` sub-command to list candidates for removal.

In some cases, we keep unused states if they are simple and haven't needed changes. At time of writing, these include ``nodejs``, ``react_apps``, ``yarn`` and ``redis``.

.. _inspect-package:

Inspect packages
----------------

Connect to the server and:

-  Show what files the package installs:

   .. code-block:: bash

      dpkg -L PACKAGE

-  Show what packages the package depends on (after ``Depends:`` and ``Recommends:``):

   .. code-block:: bash

      apt show PACKAGE

-  Show what packages depends on this package:

   .. code-block:: bash

      apt rdepends PACKAGE

For example, the above commands show that ``redis`` is a metapackage (installing only documentation) that depends on ``redis-server``, and that ``python3-virtualenv`` provides library files whereas ``virtualenv`` provides a binary file (needed by Salt).

List manually installed packages
--------------------------------

This `StackOverflow answer <https://unix.stackexchange.com/a/141001>`__ works best., However, on Hetzner and Linode servers, the ``/var/log/installer`` directory is missing. The Ubuntu manifest can be used as an approximation, for example:

.. code-block:: bash

   comm -23 <(apt-mark showmanual | sort -u) <(curl -sS https://releases.ubuntu.com/bionic/ubuntu-18.04.5-live-server-amd64.manifest | cut -f1 | cut -d: -f1 | sort -u)

..
   https://unix.stackexchange.com/a/80520 is similar. Instead of `apt-mark showmanual`, it takes the packages that
   appear in `dpkg-query --show` and not in `apt-mark showauto`. The output includes linux-* packages.

   https://askubuntu.com/a/1279044 uses /var/log/installer/status (unavailable on Ubuntu 18.04).

   https://stackoverflow.com/a/60252818/244258 uses /var/log/installer/syslog (outputs more dependencies).

..
   Some other dead ends are...

   dpkg includes all dependencies:

      dpkg --get-selections | grep -v deinstall
      dpkg --list
      dpkg-query --list
      dpkg-query --show

   apt includes system packages:

      apt-mark showmanual
      apt list --manual-installed

   /var/log/apt/history.log has incomplete history.

      zgrep ' install ' /var/log/apt/history.log* | grep -oP '[^ ]+$' | sort

   /var/log/apt/term.log includes some dependencies.

      zgrep -oP 'package \K.+\.' /var/log/apt/term.log* | sed 's/\.$//' | cut -d: -f2 | sort | grep -v linux-

   /var/log/dpkg.log includes some dependencies, and any packages that were later removed.

      zgrep '[0-9] install' /var/log/dpkg.log* | cut -d' ' -f4 | cut -d: -f1 | sort | grep -v linux-