db3a3fee05
- sfdisk - partitions the disk - mkfs - formats partitions - mkswap - formats partitions for swap - systemd.mount - explicit creation of systemd mount units - systemd.swap - explicit creation of systemd swap units Signed-off-by: Jonathon Anderson <janderson@ciq.com>
149 lines
4.8 KiB
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149 lines
4.8 KiB
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==================
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Provisioning disks
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==================
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As a tech preview, Warewulf provides structures to define disks, partitions, and
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file systems. These structures can generate a configuration for `Ignition`_ to
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provision partitions and file systems dynamically on cluster nodes, or with
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sfdisk, mkfs, and mkswap during boot.
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.. _Ignition: https://coreos.github.io/ignition/
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Ignition can, for example, create ``swap`` partitions or ``/scratch`` file
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systems.
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.. note::
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Warewulf is not currently able to provision the node image onto an explicitly
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provisioned root file system.
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Requirements
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============
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Partition and file system creation requires both ``ignition`` and ``sgdisk`` to
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be installed in the image.
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Rocky Linux
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-----------
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.. code-block:: shell
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dnf install ignition gdisk
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.. note::
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Packages for Ignition are not currently available for Rocky Linux 8, but it
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is available for Rocky Linux 9 as part of "appstream."
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openSuse Leap
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-------------
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.. code-block:: shell
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zypper install ignition gptfdisk
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Disks and partitions
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====================
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A node or profile can have several disks. Each disk is identified by the path to
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its block device. Each disk holds a map to its partitions and a ``bool`` switch
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to indicate if an existing, non-matching partition table should be overwritten.
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Each partition is identified by its label. The partition number can be omitted,
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but specifying it is recommended as Ignition may fail without it. Partition
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sizes should also be set (specified in MiB), except for the last partition: if
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no size is given, the maximum available size is used. Each partition has the
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switches ``should_exist`` and ``wipe_partition_entry`` which control the
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partition creation process. When omitting a partition number the
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`wipe_partition_entry` should be true, as this allows ignition to replace the
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existing partition.
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.. code-block:: shell
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wwctl node set n1 \
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--diskname /dev/vda --diskwipe \
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--partname scratch --partcreate --partnumber 1
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File systems
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============
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File systems are identified by their underlying block device, preferably using
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the ``/dev/by-partlabel`` format. Except for a ``swap`` partition, an absolute
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path for the mount point must be specified for each file system. Depending on
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the image used, valid formats are ``btrfs``, ``ext3``, ``ext4``, and ``xfs``.
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Each file system has the switch ``wipe_filesystem`` to control whether an
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existing file system is wiped.
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.. code-block:: shell
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wwctl node set n1 \
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--diskname /dev/vda --partname scratch \
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--fsname scratch --fsformat btrfs --fspath /scratch
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Boot-time configuration
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=======================
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Ignition uses systemd, as the underlying ``sgdisk`` command relies on dbus
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notifications.
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1. ``ignition-disks-ww4.service`` uses Ignition to create the specified
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partitions and file systems.
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2. ``ww4-disks.target`` depends on a matching ``.mount`` unit for each
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mounted file system.
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3. Each ``.mount`` creates the necessary mount points in the root file system
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and mounts the provisioned file systems during boot.
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These services and mount units are generated by the ``ignition`` overlay and
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depend on the existence of the file ``/warewulf/ignition.json``, also generated
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by the ``ignition`` overlay.
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Example disk configurations
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===========================
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This command formats a btrfs file system on a "scratch" partion of
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"vda" and mounts it at ``/scratch``.
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.. code-block:: shell
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wwctl node set n1 \
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--diskname /dev/vda --diskwipe \
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--partname scratch --partcreate --partnumber 1 \
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--fsname scratch --fsformat btrfs --fspath /scratch
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This command adds a swap partition to the "vda" disk.
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.. code-block:: shell
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wwctl node set n1 \
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--diskname /dev/vda \
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--partname swap --partsize=1024 --partnumber 2 \
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--fsname swap --fsformat swap --fspath swap
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Re-using or wiping disks
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========================
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For empty disks the desired configuration is created and the filesystems are
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mounted. If partitions or file systems already exist on the disk, ``ignition``
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tries to reuse existing file systems by default.
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To ignore existing file systems and provision fresh file systems on each boot,
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specify the ``--fswipe``` flag for that filesystem, and ``--diskwipe`` for the
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disk, as necessary.
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If you would like to re-use existing partitions but want to replace existing
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file systems once, you may
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* wipe the existing data with tools like ``wipefs`` or `dd` [#]_; or
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* set the ``--fswipe`` flag and remove it after one reboot.
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.. [#] With ``wipefs`` you have to remove the filesystem *and* parition
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information. E.g., use ``wipefs -fa /dev/vda*`` to remove all file system
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information and partition information.
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See the `upstream ignition documentation`_ for additional information.
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.. _upstream ignition documentation: https://coreos.github.io/ignition/operator-notes/#filesystem-reuse-semantics
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