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Taikun OCP Guide

Table of Contents

Node cleaning

Overview

Ironic provides two modes for node cleaning: automated
and manual.

Automated cleaning is automatically performed before the
first workload has been assigned to a node and when hardware is recycled
from one workload to another.

Manual cleaning must be invoked by the operator.

Automated cleaning

When hardware is recycled from one workload to another, ironic
performs automated cleaning on the node to ensure it’s ready for another
workload. This ensures the tenant will get a consistent bare metal node
deployed every time.

Ironic implements automated cleaning by collecting a list of cleaning
steps to perform on a node from the Power, Deploy, Management, BIOS, and
RAID interfaces of the driver assigned to the node. These steps are then
ordered by priority and executed on the node when the node is moved to
cleaning state, if automated cleaning is enabled.

With automated cleaning, nodes move to cleaning state
when moving from active -> available state
(when the hardware is recycled from one workload to another). Nodes also
traverse cleaning when going from manageable ->
available state (before the first workload is assigned to
the nodes). For a full understanding of all state transitions into
cleaning, please see states.

Ironic added support for automated cleaning in the Kilo release.

Enabling automated cleaning

To enable automated cleaning, ensure that your ironic.conf is set as
follows:

[conductor]
automated_clean=true

This will enable the default set of cleaning steps, based on your
hardware and ironic hardware types used for nodes. This includes, by
default, erasing all of the previous tenant’s data.

You may also need to configure a Cleaning
Network
.

Cleaning steps

Cleaning steps used for automated cleaning are ordered from higher to
lower priority, where a larger integer is a higher priority. In case of
a conflict between priorities across interfaces, the following
resolution order is used: Power, Management, Deploy, BIOS, and RAID
interfaces.

You can skip a cleaning step by setting the priority for that
cleaning step to zero or ‘None’.

You can reorder the cleaning steps by modifying the integer
priorities of the cleaning steps.

See How do
I change the priority of a cleaning step?
for more information.

Storage cleaning options

Clean steps specific to storage are erase_devices,
erase_devices_metadata and (added in Yoga)
erase_devices_express.

erase_devices aims to ensure that the data is removed in
the most secure way available. On devices that support hardware assisted
secure erasure (many NVMe and some ATA drives) this is the preferred
option. If hardware-assisted secure erasure is not available and if
[deploy]/continue_if_disk_secure_erase_fails is set to
True, cleaning will fall back to using shred
to overwrite the contents of the device. Otherwise cleaning will fail.
It is important to note that erase_devices may take a very
long time (hours or even days) to complete, unless fast, hardware
assisted data erasure is supported by all the devices in a system.
Generally, it is very difficult (if possible at all) to recover data
after performing cleaning with erase_devices.

erase_devices_metadata clean step doesn’t provide as
strong assurance of irreversible destruction of data as
erase_devices. However, it has the advantage of a
reasonably quick runtime (seconds to minutes). It operates by destroying
metadata of the storage device without erasing every bit of the data
itself. Attempts of restoring data after running
erase_devices_metadata may be successful but would
certainly require relevant expertise and specialized tools.

Lastly, erase_devices_express combines some of the perks
of both erase_devices and
erase_devices_metadata. It attempts to utilize hardware
assisted data erasure features if available (currently only NVMe devices
are supported). In case hardware-asssisted data erasure is not
available, it falls back to metadata erasure for the device (which is
identical to erase_devices_metadata). It can be considered
a time optimized mode of storage cleaning, aiming to perform as thorough
data erasure as it is possible within a short period of time. This clean
step is particularly well suited for environments with hybrid NVMe-HDD
storage configuration as it allows fast and secure erasure of data
stored on NVMes combined with equally fast but more basic metadata-based
erasure of data on HDDs. erase_devices_express is disabled
by default. In order to use it, the following configuration is
recommended.

[deploy]/erase_devices_priority=0
[deploy]/erase_devices_metadata_priority=0
[conductor]/clean_step_priority_override=deploy.erase_devices_express:5

This ensures that erase_devices and
erase_devices_metadata are disabled so that storage is not
cleaned twice and then assigns a non-zero priority to
erase_devices_express, hence enabling it. Any non-zero
priority specified in the priority override will work.

Also [deploy]/enable_nvme_secure_erase
should not be disabled (it is on by default).

Manual cleaning

Manual cleaning is typically used to handle long
running, manual, or destructive tasks that an operator wishes to perform
either before the first workload has been assigned to a node or between
workloads. When initiating a manual clean, the operator specifies the
cleaning steps to be performed. Manual cleaning can only be performed
when a node is in the manageable state. Once the manual
cleaning is finished, the node will be put in the
manageable state again.

Ironic added support for manual cleaning in the 4.4 (Mitaka series)
release.

Setup

In order for manual cleaning to work, you may need to configure a Cleaning Network.

Starting manual cleaning via
API

Manual cleaning can only be performed when a node is in the
manageable state. The REST API request to initiate it is
available in API version 1.15 and higher:

PUT /v1/nodes/<node_ident>/states/provision

(Additional information is available here.)

This API will allow operators to put a node directly into
cleaning provision state from manageable state
via ‘target’: ‘clean’. The PUT will also require the argument
‘clean_steps’ to be specified. This is an ordered list of cleaning
steps. A cleaning step is represented by a dictionary (JSON), in the
form:

{
    "interface": "<interface>",
    "step": "<name of cleaning step>",
    "args": {"<arg1>": "<value1>", ..., "<argn>": <valuen>}
}

The ‘interface’ and ‘step’ keys are required for all steps. If a
cleaning step method takes keyword arguments, the ‘args’ key may be
specified. It is a dictionary of keyword variable arguments, with each
keyword-argument entry being <name>: <value>.

If any step is missing a required keyword argument, manual cleaning
will not be performed and the node will be put in
clean failed provision state with an appropriate error
message.

If, during the cleaning process, a cleaning step determines that it
has incorrect keyword arguments, all earlier steps will be performed and
then the node will be put in clean failed provision state
with an appropriate error message.

An example of the request body for this API:

{
  "target":"clean",
  "clean_steps": [{
    "interface": "raid",
    "step": "create_configuration",
    "args": {"create_nonroot_volumes": false}
  },
  {
    "interface": "deploy",
    "step": "erase_devices"
  }]
}

In the above example, the node’s RAID interface would configure
hardware RAID without non-root volumes, and then all devices would be
erased (in that order).

Starting
manual cleaning via “openstack metal” CLI

Manual cleaning is available via the
baremetal node clean command, starting with Bare Metal API
version 1.15.

The argument --clean-steps must be specified. Its value
is one of:

  • a JSON string
  • path to a JSON file whose contents are passed to the API
  • ‘-‘, to read from stdin. This allows piping in the clean steps.
    Using ‘-‘ to signify stdin is common in Unix utilities.

The following examples assume that the Bare Metal API version was set
via the OS_BAREMETAL_API_VERSION environment variable. (The
alternative is to add --os-baremetal-api-version 1.15 to
the command.):

export OS_BAREMETAL_API_VERSION=1.15

Examples of doing this with a JSON string:

baremetal node clean <node> \
    --clean-steps '[{"interface": "deploy", "step": "erase_devices_metadata"}]'

baremetal node clean <node> \
    --clean-steps '[{"interface": "deploy", "step": "erase_devices"}]'

Or with a file:

baremetal node clean <node> \
    --clean-steps my-clean-steps.txt

Or with stdin:

cat my-clean-steps.txt | baremetal node clean <node> \
    --clean-steps -

Cleaning Network

If you are using the Neutron DHCP provider (the default) you will
also need to ensure you have configured a cleaning network. This network
will be used to boot the ramdisk for in-band cleaning. You can use the
same network as your tenant network. For steps to set up the cleaning
network, please see configure-cleaning.

In-band vs out-of-band

Ironic uses two main methods to perform actions on a node: in-band
and out-of-band. Ironic supports using both methods to clean a node.

In-band

In-band steps are performed by ironic making API calls to a ramdisk
running on the node using a deploy interface. Currently, all the deploy
interfaces support in-band cleaning. By default, ironic-python-agent
ships with a minimal cleaning configuration, only erasing disks.
However, you can add your own cleaning steps and/or override default
cleaning steps with a custom Hardware Manager.

Out-of-band

Out-of-band are actions performed by your management controller, such
as IPMI, iLO, or DRAC. Out-of-band steps will be performed by ironic
using a power or management interface. Which steps are performed depends
on the hardware type and hardware itself.

For Out-of-Band cleaning operations supported by iLO hardware types,
refer to ilo_node_cleaning.

FAQ

How are cleaning steps
ordered?

For automated cleaning, cleaning steps are ordered by integer
priority, where a larger integer is a higher priority. In case of a
conflict between priorities across hardware interfaces, the following
resolution order is used:

  1. Power interface
  2. Management interface
  3. Deploy interface
  4. BIOS interface
  5. RAID interface

For manual cleaning, the cleaning steps should be specified in the
desired order.

How do I skip a cleaning
step?

For automated cleaning, cleaning steps with a priority of 0 or None
are skipped.

How do I change
the priority of a cleaning step?

For manual cleaning, specify the cleaning steps in the desired
order.

For automated cleaning, it depends on whether the cleaning steps are
out-of-band or in-band.

Most out-of-band cleaning steps have an explicit configuration option
for priority.

Changing the priority of an in-band (ironic-python-agent) cleaning
step requires use of a custom HardwareManager. The only exception is
erase_devices, which can have its priority set in
ironic.conf. For instance, to disable erase_devices, you’d set the
following configuration option:

[deploy]
erase_devices_priority=0

To enable/disable the in-band disk erase using ilo
hardware type, use the following configuration option:

[ilo]
clean_priority_erase_devices=0

The generic hardware manager first identifies whether a device is an
NVMe drive or an ATA drive so that it can attempt a platform-specific
secure erase method. In case of NVMe drives, it tries to perform a
secure format operation by using the nvme-cli utility. This
behavior can be controlled using the following configuration option (by
default it is set to True):

[deploy]
enable_nvme_secure_erase=True

In case of ATA drives, it tries to perform ATA disk erase by using
the hdparm utility.

If neither method is supported, it performs software based disk erase
using the shred utility. By default, the number of
iterations performed by shred for software based disk erase
is 1. To configure the number of iterations, use the following
configuration option:

[deploy]
erase_devices_iterations=1

Overriding step priority

[conductor]clean_step_priority_override is a new
configuration option which allows specifying priority of each step using
multiple configuration values:

[conductor]
clean_step_priority_override=deploy.erase_devices_metadata:123
clean_step_priority_override=management.reset_bios_to_default:234
clean_step_priority_override=management.clean_priority_reset_ilo:345

This parameter can be specified as many times as required to define
priorities for several cleaning steps – the values will be combined.

What cleaning step is
running?

To check what cleaning step the node is performing or attempted to
perform and failed, run the following command; it will return the value
in the node’s driver_internal_info field:

baremetal node show $node_ident -f value -c driver_internal_info

The clean_steps field will contain a list of all
remaining steps with their priorities, and the first one listed is the
step currently in progress or that the node failed before going into
clean failed state.

Should I disable automated
cleaning?

Automated cleaning is recommended for ironic deployments, however,
there are some tradeoffs to having it enabled. For instance, ironic
cannot deploy a new instance to a node that is currently cleaning, and
cleaning can be a time consuming process. To mitigate this, we suggest
using NVMe drives with support for NVMe Secure Erase (based on
nvme-cli format command) or ATA drives with support for
cryptographic ATA Security Erase, as typically the erase_devices step in
the deploy interface takes the longest time to complete of all cleaning
steps.

Why can’t I
power on/off a node while it’s cleaning?

During cleaning, nodes may be performing actions that shouldn’t be
interrupted, such as BIOS or Firmware updates. As a result, operators
are forbidden from changing power state via the ironic API while a node
is cleaning.

Troubleshooting

If cleaning fails on a node, the node will be put into
clean failed state. If the failure happens while running a
clean step, the node is also placed in maintenance mode to prevent
ironic from taking actions on the node. The operator should validate
that no permanent damage has been done to the node and no processes are
still running on it before removing the maintenance mode.

Note

Older versions of ironic may put the node to maintenance even when no
clean step has been running.

Nodes in clean failed will not be powered off, as the
node might be in a state such that powering it off could damage the node
or remove useful information about the nature of the cleaning
failure.

A clean failed node can be moved to
manageable state, where it cannot be scheduled by nova and
you can safely attempt to fix the node. To move a node from
clean failed to manageable:

baremetal node manage $node_ident

You can now take actions on the node, such as replacing a bad disk
drive.

Strategies for determining why a cleaning step failed include
checking the ironic conductor logs, viewing logs on the still-running
ironic-python-agent (if an in-band step failed), or performing general
hardware troubleshooting on the node.

When the node is repaired, you can move the node back to
available state, to allow it to be scheduled by nova.

# First, move it out of maintenance mode
baremetal node maintenance unset $node_ident

# Now, make the node available for scheduling by nova
baremetal node provide $node_ident

The node will begin automated cleaning from the start, and move to
available state when complete.

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