===
 FAQ
 ===

 
 -  `General Questions <#general>`__
 -  `Operation and Configuration <#ops_conf>`__
 -  `Miscellaneous <#misc>`__
 
 General Questions

 =================

 
 Q: Can I use DevStack for production?
     A: No. We mean it. Really. DevStack makes some implementation
     choices that are not appropriate for production deployments. We
     warned you!
 Q: Then why selinux in enforcing mode?
     A: That is the default on current Fedora and RHEL releases. DevStack
     has (rightly so) a bad reputation for its security practices; it has
     always been meant as a development tool first and system integration
     later. This is changing as the security issues around OpenStack's
     use of root (for example) have been tightened and developers need to
     be better equipped to work in these environments. ``stack.sh``'s use
     of root is primarily to support the activities that would be handled
     by packaging in "real" deployments. To remove additional protections
     that will be desired/required in production would be a step
     backward.

 Q: But selinux is disabled in RHEL!

     A: Today it is, yes. That is a specific exception that certain
     DevStack contributors fought strongly against. The primary reason it
     was allowed was to support using RHEL6 as the Python 2.6 test
     platform and that took priority time-wise. This will not be the case
     with RHEL 7.
 Q: Why a shell script, why not chef/puppet/...
     A: The script is meant to be read by humans (as well as ran by
     computers); it is the primary documentation after all. Using a
     recipe system requires everyone to agree and understand chef or
     puppet.
 Q: Why not use Crowbar?
     A: DevStack is optimized for documentation & developers. As some of
     us use `Crowbar <https://github.com/dellcloudedge/crowbar>`__ for
     production deployments, we hope developers documenting how they
     setup systems for new features supports projects like Crowbar.
 Q: I'd like to help!
     A: That isn't a question, but please do! The source for DevStack is
     at
     `git.openstack.org <https://git.openstack.org/cgit/openstack-dev/devstack>`__
     and bug reports go to
     `LaunchPad <http://bugs.launchpad.net/devstack/>`__. Contributions

     follow the usual process as described in the `developer
     guide <http://docs.openstack.org/infra/manual/developers.html>`__. This Sphinx

     documentation is housed in the doc directory.

 Q: Why not use packages?
     A: Unlike packages, DevStack leaves your cloud ready to develop -
     checkouts of the code and services running in screen. However, many
     people are doing the hard work of packaging and recipes for
     production deployments. We hope this script serves as a way to
     communicate configuration changes between developers and packagers.
 Q: Why isn't $MY\_FAVORITE\_DISTRO supported?
     A: DevStack is meant for developers and those who want to see how
     OpenStack really works. DevStack is known to run on the
     distro/release combinations listed in ``README.md``. DevStack is
     only supported on releases other than those documented in
     ``README.md`` on a best-effort basis.
 Q: What about Fedora/RHEL/CentOS?
     A: Fedora and CentOS/RHEL are supported via rpm dependency files and
     specific checks in ``stack.sh``. Support will follow the pattern set
     with the Ubuntu testing, i.e. only a single release of the distro
     will receive regular testing, others will be handled on a
     best-effort basis.
 Q: Are there any differences between Ubuntu and Fedora support?
     A: Neutron is not fully supported prior to Fedora 18 due lack of
     OpenVSwitch packages.

 Q: Why can't I use another shell?
     A: DevStack now uses some specific bash-ism that require Bash 4, such
     as associative arrays. Simple compatibility patches have been accepted
     in the past when they are not complex, at this point no additional
     compatibility patches will be considered except for shells matching
     the array functionality as it is very ingrained in the repo and project
     management.
 Q: But, but, can't I test on OS/X?
    A: Yes, even you, core developer who complained about this, needs to
    install bash 4 via homebrew to keep running tests on OS/X.  Get a Real
    Operating System.   (For most of you who don't know, I am refering to
    myself.)

 
 Operation and Configuration

 ===========================

 
 Q: Can DevStack handle a multi-node installation?
     A: Indirectly, yes. You run DevStack on each node with the
     appropriate configuration in ``local.conf``. The primary
     considerations are turning off the services not required on the
     secondary nodes, making sure the passwords match and setting the
     various API URLs to the right place.
 Q: How can I document the environment that DevStack is using?
     A: DevStack includes a script (``tools/info.sh``) that gathers the
     versions of the relevant installed apt packages, pip packages and
     git repos. This is a good way to verify what Python modules are
     installed.
 Q: How do I turn off a service that is enabled by default?
     A: Services can be turned off by adding ``disable_service xxx`` to
     ``local.conf`` (using ``n-vol`` in this example):
 
     ::
 
         disable_service n-vol
 
 Q: Is enabling a service that defaults to off done with the reverse of the above?
     A: Of course!
 
     ::
 
         enable_service qpid
 
 Q: How do I run a specific OpenStack milestone?
     A: OpenStack milestones have tags set in the git repo. Set the appropriate tag in the ``*_BRANCH`` variables in ``local.conf``.  Swift is on its own release schedule so pick a tag in the Swift repo that is just before the milestone release. For example:
 
     ::
 
         [[local|localrc]]
         GLANCE_BRANCH=stable/grizzly
         HORIZON_BRANCH=stable/grizzly
         KEYSTONE_BRANCH=stable/grizzly
         NOVA_BRANCH=stable/grizzly
         GLANCE_BRANCH=stable/grizzly
         NEUTRON_BRANCH=stable/grizzly
         SWIFT_BRANCH=1.10.0
 
 Q: Why not use [STRIKEOUT:``tools/pip-requires``]\ ``requirements.txt`` to grab project dependencies?
     [STRIKEOUT:The majority of deployments will use packages to install
     OpenStack that will have distro-based packages as dependencies.
     DevStack installs as many of these Python packages as possible to

     mimic the expected production environment.] Certain Linux

     distributions have a 'lack of workaround' in their Python
     configurations that installs vendor packaged Python modules and
     pip-installed modules to the SAME DIRECTORY TREE. This is causing
     heartache and moving us in the direction of installing more modules
     from PyPI than vendor packages. However, that is only being done as
     necessary as the packaging needs to catch up to the development
     cycle anyway so this is kept to a minimum.
 Q: What can I do about RabbitMQ not wanting to start on my fresh new VM?
     A: This is often caused by ``erlang`` not being happy with the
     hostname resolving to a reachable IP address. Make sure your
     hostname resolves to a working IP address; setting it to 127.0.0.1
     in ``/etc/hosts`` is often good enough for a single-node
     installation. And in an extreme case, use ``clean.sh`` to eradicate
     it and try again.
 Q: How can I set up Heat in stand-alone configuration?
     A: Configure ``local.conf`` thusly:
 
     ::
 
         [[local|localrc]]
         HEAT_STANDALONE=True
         ENABLED_SERVICES=rabbit,mysql,heat,h-api,h-api-cfn,h-api-cw,h-eng
         KEYSTONE_SERVICE_HOST=<keystone-host>
         KEYSTONE_AUTH_HOST=<keystone-host>
 
 Q: Why are my configuration changes ignored?
     A: You may have run into the package prerequisite installation
     timeout. ``tools/install_prereqs.sh`` has a timer that skips the
     package installation checks if it was run within the last
     ``PREREQ_RERUN_HOURS`` hours (default is 2). To override this, set
     ``FORCE_PREREQ=1`` and the package checks will never be skipped.
 
 Miscellaneous

 =============

 
 Q: ``tools/fixup_stuff.sh`` is broken and shouldn't 'fix' just one version of packages.
     A: [Another not-a-question] No it isn't. Stuff in there is to
     correct problems in an environment that need to be fixed elsewhere
     or may/will be fixed in a future release. In the case of
     ``httplib2`` and ``prettytable`` specific problems with specific
     versions are being worked around. If later releases have those
     problems than we'll add them to the script. Knowing about the broken
     future releases is valuable rather than polling to see if it has
     been fixed.