129 lines
3.9 KiB
ReStructuredText
129 lines
3.9 KiB
ReStructuredText
PreOS
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=====
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Description
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-----------
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With cdist you can install and configure new machines. You can use cdist to
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create PreOS, minimal OS whose purpose is to boot a new machine.
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After PreOS is booted, the machine is ready for installing the desired OS and
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afterwards it is ready for configuration.
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PreOS creation
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--------------
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With cdist you can create PreOS.
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Currently supported PreOS-es include:
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* debian
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* ubuntu
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* devuan
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PreOS is created using the ``cdist preos`` command.
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This command has subcommands that determine the desired PreOS.
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For example, to create an ubuntu PreOS:
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.. code-block:: sh
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$ cdist preos ubuntu /preos/preos-ubuntu -B -C \
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-k ~/.ssh/id_rsa.pub -p /preos/pxe-ubuntu
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For more info about the available options see the cdist manual page.
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This will bootstrap (``-B``) ubuntu PreOS in the ``/preos/preos-ubuntu``
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directory, it will be configured (``-C``) using default the built-in initial
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manifest and with specified ssh authorized key (``-k``).
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After bootstrapping and configuration, the PXE boot directory will be
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created (``-p``) in ``/preos/pxe-ubuntu``.
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After PreOS is created, new machines can be booted using the created PXE
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(after proper dhcp and tftp settings).
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Since PreOS is configured with ssh authorized key it can be accessed through
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ssh, i.e. it can be further installed and configured with cdist.
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Implementing a new PreOS sub-command
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------------------------------------
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preos command is implemented as a plugin system. This plugin system scans for
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preos subcommands in the ``cdist/preos/`` distribution directory and also in
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``~/.cdist/preos/`` directory if it exists.
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preos subcommand is a module or a class that satisfies the following:
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* it has the attribute ``_cdist_preos`` set to ``True``
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* it defines a function/method ``commandline``.
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For a module-based preos subcommand, the ``commandline`` function accepts a
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module object as its first argument and the list of command line
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arguments (``sys.argv[2:]``).
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For a class-based preos subcommand ``commandline`` method should be
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static-method and must accept a class as its first argument and the
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list of command line arguments (``sys.argv[2:]``).
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If preos scanning finds a module/class that has ``_cdist_preos`` set
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to ``True`` and a function/method ``commandline`` then this module/class is
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registered to preos subcommands. The name of the command is set to ``_preos_name``
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attribute if defined in the module/class, defaulting to the module/class name in lowercase.
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When a registered preos subcommand is specified, ``commandline``
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will be called with the first argument set to module/class and the second
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argument set to ``sys.argv[2:]``.
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Example of writing new dummy preos sub-command
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Module-based preos:
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^^^^^^^^^^^^^^^^^^^
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#. Create directory ``~/.cdist/preos/`` if it does not exist
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#. Create ``~/.cdist/preos/netbsd.py`` with the following contents:
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.. code-block:: python
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_preos_name = 'netbsd'
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_cdist_preos = True
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def commandline(cls, args):
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print("NetBSD PreOS: {}".format(args))
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When you try to run this new preos you will get:
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.. code-block:: sh
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$ cdist preos -L
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Available PreOS-es:
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- debian
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- devuan
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- netbsd
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- ubuntu
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$ cdist preos netbsd
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NetBSD PreOS: []
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Class based preos:
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^^^^^^^^^^^^^^^^^^
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#. Create directory ``~/.cdist/preos/`` if it does not exist
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#. Create ``~/.cdist/preos/freebsd.py`` with the following contents:
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.. code-block:: python
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class FreeBSD(object):
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_cdist_preos = True
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@classmethod
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def commandline(cls, args):
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print("FreeBSD dummy preos: {}".format(args))
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When you try to run this new preos you will get:
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.. code-block:: sh
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$ cdist preos -h
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Available PreOS-es:
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- debian
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- devuan
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- freebsd
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- ubuntu
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$ cdist preos freebsd
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FreeBSD dummy preos: []
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In the ``commandline`` function/method you have all the freedom to actually create
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a PreOS.
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