.. _configuring-ceph:

==================
 Configuring Ceph
==================

When Ceph services start, the initialization process activates a series
of daemons that run in the background. A :term:`Ceph Storage Cluster` runs 
at a minimum three types of daemons:

- :term:`Ceph Monitor` (``ceph-mon``)
- :term:`Ceph Manager` (``ceph-mgr``)
- :term:`Ceph OSD Daemon` (``ceph-osd``)

Ceph Storage Clusters that support the :term:`Ceph File System` also run at
least one :term:`Ceph Metadata Server` (``ceph-mds``). Clusters that
support :term:`Ceph Object Storage` run Ceph RADOS Gateway daemons
(``radosgw``) as well.

Each daemon has a number of configuration options, each of which has a
default value.  You may adjust the behavior of the system by changing these
configuration options.  Be careful to understand the consequences before
overriding default values, as it is possible to significantly degrade the
performance and stability of your cluster.  Also note that default values
sometimes change between releases, so it is best to review the version of
this documentation that aligns with your Ceph release.

Option names
============

All Ceph configuration options have a unique name consisting of words
formed with lower-case characters and connected with underscore
(``_``) characters.

When option names are specified on the command line, either underscore
(``_``) or dash (``-``) characters can be used interchangeable (e.g.,
``--mon-host`` is equivalent to ``--mon_host``).

When option names appear in configuration files, spaces can also be
used in place of underscore or dash.  We suggest, though, that for
clarity and convenience you consistently use underscores, as we do
throughout this documentation.

Config sources
==============

Each Ceph daemon, process, and library will pull its configuration
from several sources, listed below.  Sources later in the list will
override those earlier in the list when both are present.

- the compiled-in default value
- the monitor cluster's centralized configuration database
- a configuration file stored on the local host
- environment variables
- command line arguments
- runtime overrides set by an administrator

One of the first things a Ceph process does on startup is parse the
configuration options provided via the command line, environment, and
local configuration file.  The process will then contact the monitor
cluster to retrieve configuration stored centrally for the entire
cluster.  Once a complete view of the configuration is available, the
daemon or process startup will proceed.

.. _bootstrap-options:

Bootstrap options
-----------------

Because some configuration options affect the process's ability to
contact the monitors, authenticate, and retrieve the cluster-stored
configuration, they may need to be stored locally on the node and set
in a local configuration file.  These options include:

  - ``mon_host``, the list of monitors for the cluster
  - ``mon_host_override``, the list of monitors for the cluster to
    **initially** contact when beginning a new instance of communication with the
    Ceph cluster.  This overrides the known monitor list derived from MonMap
    updates sent to older Ceph instances (like librados cluster handles).  It is
    expected this option is primarily useful for debugging.
  - ``mon_dns_srv_name`` (default: `ceph-mon`), the name of the DNS
    SRV record to check to identify the cluster monitors via DNS
  - ``mon_data``, ``osd_data``, ``mds_data``, ``mgr_data``, and
    similar options that define which local directory the daemon
    stores its data in.
  - ``keyring``, ``keyfile``, and/or ``key``, which can be used to
    specify the authentication credential to use to authenticate with
    the monitor.  Note that in most cases the default keyring location
    is in the data directory specified above.

In the vast majority of cases the default values of these are
appropriate, with the exception of the ``mon_host`` option that
identifies the addresses of the cluster's monitors.  When DNS is used
to identify monitors a local ceph configuration file can be avoided
entirely.

Skipping monitor config
-----------------------

Any process may be passed the option ``--no-mon-config`` to skip the
step that retrieves configuration from the cluster monitors.  This is
useful in cases where configuration is managed entirely via
configuration files or where the monitor cluster is currently down but
some maintenance activity needs to be done.


.. _ceph-conf-file:


Configuration sections
======================

Any given process or daemon has a single value for each configuration
option.  However, values for an option may vary across different
daemon types even daemons of the same type.  Ceph options that are
stored in the monitor configuration database or in local configuration
files are grouped into sections to indicate which daemons or clients
they apply to.

These sections include:

``global``

:Description: Settings under ``global`` affect all daemons and clients
              in a Ceph Storage Cluster.

:Example: ``log_file = /var/log/ceph/$cluster-$type.$id.log``

``mon``

:Description: Settings under ``mon`` affect all ``ceph-mon`` daemons in
              the Ceph Storage Cluster, and override the same setting in 
              ``global``.

:Example: ``mon_cluster_log_to_syslog = true``


``mgr``

:Description: Settings in the ``mgr`` section affect all ``ceph-mgr`` daemons in
              the Ceph Storage Cluster, and override the same setting in 
              ``global``.

:Example: ``mgr_stats_period = 10``

``osd``

:Description: Settings under ``osd`` affect all ``ceph-osd`` daemons in
              the Ceph Storage Cluster, and override the same setting in
              ``global``.

:Example: ``osd_op_queue = wpq``

``mds``

:Description: Settings in the ``mds`` section affect all ``ceph-mds`` daemons in
              the Ceph Storage Cluster, and override the same setting in
              ``global``.

:Example: ``mds_cache_memory_limit = 10G``

``client``

:Description: Settings under ``client`` affect all Ceph Clients
              (e.g., mounted Ceph File Systems, mounted Ceph Block Devices,
              etc.) as well as Rados Gateway (RGW) daemons.

:Example: ``objecter_inflight_ops = 512``


Sections may also specify an individual daemon or client name.  For example,
``mon.foo``, ``osd.123``, and ``client.smith`` are all valid section names.


Any given daemon will draw its settings from the global section, the
daemon or client type section, and the section sharing its name.
Settings in the most-specific section take precedence, so for example
if the same option is specified in both ``global``, ``mon``, and
``mon.foo`` on the same source (i.e., in the same configurationfile),
the ``mon.foo`` value will be used.

If multiple values of the same configuration option are specified in the same
section, the last value wins.

Note that values from the local configuration file always take
precedence over values from the monitor configuration database,
regardless of which section they appear in.


.. _ceph-metavariables:

Metavariables
=============

Metavariables simplify Ceph Storage Cluster configuration
dramatically. When a metavariable is set in a configuration value,
Ceph expands the metavariable into a concrete value at the time the
configuration value is used. Ceph metavariables are similar to variable expansion in the Bash shell.

Ceph supports the following metavariables: 

``$cluster``

:Description: Expands to the Ceph Storage Cluster name. Useful when running 
              multiple Ceph Storage Clusters on the same hardware.

:Example: ``/etc/ceph/$cluster.keyring``
:Default: ``ceph``


``$type``

:Description: Expands to a daemon or process type (e.g., ``mds``, ``osd``, or ``mon``)

:Example: ``/var/lib/ceph/$type``


``$id``

:Description: Expands to the daemon or client identifier. For
              ``osd.0``, this would be ``0``; for ``mds.a``, it would
              be ``a``.

:Example: ``/var/lib/ceph/$type/$cluster-$id``


``$host``

:Description: Expands to the host name where the process is running.


``$name``

:Description: Expands to ``$type.$id``.
:Example: ``/var/run/ceph/$cluster-$name.asok``

``$pid``

:Description: Expands to daemon pid.
:Example: ``/var/run/ceph/$cluster-$name-$pid.asok``



The Configuration File
======================

On startup, Ceph processes search for a configuration file in the
following locations:

#. ``$CEPH_CONF`` (*i.e.,* the path following the ``$CEPH_CONF``
   environment variable)
#. ``-c path/path``  (*i.e.,* the ``-c`` command line argument)
#. ``/etc/ceph/$cluster.conf``
#. ``~/.ceph/$cluster.conf``
#. ``./$cluster.conf`` (*i.e.,* in the current working directory)
#. On FreeBSD systems only, ``/usr/local/etc/ceph/$cluster.conf``

where ``$cluster`` is the cluster's name (default ``ceph``).

The Ceph configuration file uses an *ini* style syntax. You can add comment
text after a pound sign (#) or a semi-colon (;).  For example:

.. code-block:: ini

	# <--A number (#) sign precedes a comment.
	; A comment may be anything.
	# Comments always follow a semi-colon (;) or a pound (#) on each line.
	# The end of the line terminates a comment.
	# We recommend that you provide comments in your configuration file(s).


.. _ceph-conf-settings:

Config file section names
-------------------------

The configuration file is divided into sections. Each section must begin with a
valid configuration section name (see `Configuration sections`_, above)
surrounded by square brackets. For example,

.. code-block:: ini

	[global]
	debug_ms = 0
	
	[osd]
	debug_ms = 1

	[osd.1]
	debug_ms = 10

	[osd.2]
	debug_ms = 10


Config file option values
-------------------------

The value of a configuration option is a string. If it is too long to
fit in a single line, you can put a backslash (``\``) at the end of line
as the line continuation marker, so the value of the option will be
the string after ``=`` in current line combined with the string in the next
line::

  [global]
  foo = long long ago\
  long ago

In the example above, the value of "``foo``" would be "``long long ago long ago``".

Normally, the option value ends with a new line, or a comment, like

.. code-block:: ini

    [global]
    obscure_one = difficult to explain # I will try harder in next release
    simpler_one = nothing to explain

In the example above, the value of "``obscure one``" would be "``difficult to explain``";
and the value of "``simpler one`` would be "``nothing to explain``".

If an option value contains spaces, and we want to make it explicit, we
could quote the value using single or double quotes, like

.. code-block:: ini

    [global]
    line = "to be, or not to be"

Certain characters are not allowed to be present in the option values directly.
They are ``=``, ``#``, ``;`` and ``[``. If we have to, we need to escape them,
like

.. code-block:: ini

    [global]
    secret = "i love \# and \["

Every configuration option is typed with one of the types below:

``int``

:Description: 64-bit signed integer, Some SI prefixes are supported, like "K", "M", "G",
              "T", "P", "E", meaning, respectively, 10\ :sup:`3`, 10\ :sup:`6`,
              10\ :sup:`9`, etc.  And "B" is the only supported unit. So, "1K", "1M", "128B" and "-1" are all valid
              option values. Some times, a negative value implies "unlimited" when it comes to
              an option for threshold or limit.
:Example: ``42``, ``-1``

``uint``

:Description: It is almost identical to ``integer``. But a negative value will be rejected.
:Example: ``256``, ``0``

``str``

:Description: Free style strings encoded in UTF-8, but some characters are not allowed. Please
              reference the above notes for the details.
:Example: ``"hello world"``, ``"i love \#"``, ``yet-another-name``

``boolean``

:Description: one of the two values ``true`` or ``false``. But an integer is also accepted,
              where "0" implies ``false``, and any non-zero values imply ``true``.
:Example: ``true``, ``false``, ``1``, ``0``

``addr``

:Description: a single address optionally prefixed with ``v1``, ``v2`` or ``any`` for the messenger
              protocol. If the prefix is not specified, ``v2`` protocol is used. Please see
              :ref:`address_formats` for more details.
:Example: ``v1:1.2.3.4:567``, ``v2:1.2.3.4:567``, ``1.2.3.4:567``, ``2409:8a1e:8fb6:aa20:1260:4bff:fe92:18f5::567``, ``[::1]:6789``

``addrvec``

:Description: a set of addresses separated by ",". The addresses can be optionally quoted with ``[`` and ``]``.
:Example: ``[v1:1.2.3.4:567,v2:1.2.3.4:568]``, ``v1:1.2.3.4:567,v1:1.2.3.14:567``  ``[2409:8a1e:8fb6:aa20:1260:4bff:fe92:18f5::567], [2409:8a1e:8fb6:aa20:1260:4bff:fe92:18f5::568]``

``uuid``

:Description: the string format of a uuid defined by `RFC4122 <https://www.ietf.org/rfc/rfc4122.txt>`_.
              And some variants are also supported, for more details, see
              `Boost document <https://www.boost.org/doc/libs/1_74_0/libs/uuid/doc/uuid.html#String%20Generator>`_.
:Example: ``f81d4fae-7dec-11d0-a765-00a0c91e6bf6``

``size``

:Description: denotes a 64-bit unsigned integer. Both SI prefixes and IEC prefixes are
              supported. And "B" is the only supported unit. A negative value will be
              rejected.
:Example: ``1Ki``, ``1K``, ``1KiB`` and ``1B``.

``secs``

:Description: denotes a duration of time. By default the unit is second if not specified.
              Following units of time are supported:

              * second: "s", "sec", "second", "seconds"
              * minute: "m", "min", "minute", "minutes"
              * hour: "hs", "hr", "hour", "hours"
              * day: "d", "day", "days"
              * week: "w", "wk", "week", "weeks"
              * month: "mo", "month", "months"
              * year: "y", "yr", "year", "years"
:Example: ``1 m``, ``1m`` and ``1 week``

.. _ceph-conf-database:

Monitor configuration database
==============================

The monitor cluster manages a database of configuration options that
can be consumed by the entire cluster, enabling streamlined central
configuration management for the entire system.  The vast majority of
configuration options can and should be stored here for ease of
administration and transparency.

A handful of settings may still need to be stored in local
configuration files because they affect the ability to connect to the
monitors, authenticate, and fetch configuration information.  In most
cases this is limited to the ``mon_host`` option, although this can
also be avoided through the use of DNS SRV records.

Sections and masks
------------------

Configuration options stored by the monitor can live in a global
section, daemon type section, or specific daemon section, just like
options in a configuration file can.

In addition, options may also have a *mask* associated with them to
further restrict which daemons or clients the option applies to.
Masks take two forms:

#. ``type:location`` where *type* is a CRUSH property like `rack` or
   `host`, and *location* is a value for that property.  For example,
   ``host:foo`` would limit the option only to daemons or clients
   running on a particular host.
#. ``class:device-class`` where *device-class* is the name of a CRUSH
   device class (e.g., ``hdd`` or ``ssd``).  For example,
   ``class:ssd`` would limit the option only to OSDs backed by SSDs.
   (This mask has no effect for non-OSD daemons or clients.)

When setting a configuration option, the `who` may be a section name,
a mask, or a combination of both separated by a slash (``/``)
character.  For example, ``osd/rack:foo`` would mean all OSD daemons
in the ``foo`` rack.

When viewing configuration options, the section name and mask are
generally separated out into separate fields or columns to ease readability.


Commands
--------

The following CLI commands are used to configure the cluster:

* ``ceph config dump`` will dump the entire configuration database for
  the cluster.

* ``ceph config get <who>`` will dump the configuration for a specific
  daemon or client (e.g., ``mds.a``), as stored in the monitors'
  configuration database.

* ``ceph config set <who> <option> <value>`` will set a configuration
  option in the monitors' configuration database.

* ``ceph config show <who>`` will show the reported running
  configuration for a running daemon.  These settings may differ from
  those stored by the monitors if there are also local configuration
  files in use or options have been overridden on the command line or
  at run time.  The source of the option values is reported as part
  of the output.

* ``ceph config assimilate-conf -i <input file> -o <output file>``
  will ingest a configuration file from *input file* and move any
  valid options into the monitors' configuration database.  Any
  settings that are unrecognized, invalid, or cannot be controlled by
  the monitor will be returned in an abbreviated config file stored in
  *output file*.  This command is useful for transitioning from legacy
  configuration files to centralized monitor-based configuration.


Help
====

You can get help for a particular option with:

.. prompt:: bash $

   ceph config help <option>

Note that this will use the configuration schema that is compiled into the running monitors.  If you have a mixed-version cluster (e.g., during an upgrade), you might also want to query the option schema from a specific running daemon:

.. prompt:: bash $

   ceph daemon <name> config help [option]

For example:

.. prompt:: bash $

   ceph config help log_file

:: 

  log_file - path to log file
    (std::string, basic)
    Default (non-daemon):
    Default (daemon): /var/log/ceph/$cluster-$name.log
    Can update at runtime: false
    See also: [log_to_stderr,err_to_stderr,log_to_syslog,err_to_syslog]

or:

.. prompt:: bash $

   ceph config help log_file -f json-pretty

::

  {
      "name": "log_file",
      "type": "std::string",
      "level": "basic",
      "desc": "path to log file",
      "long_desc": "",
      "default": "",
      "daemon_default": "/var/log/ceph/$cluster-$name.log",
      "tags": [],
      "services": [],
      "see_also": [
          "log_to_stderr",
          "err_to_stderr",
          "log_to_syslog",
          "err_to_syslog"
      ],
      "enum_values": [],
      "min": "",
      "max": "",
      "can_update_at_runtime": false
  }

The ``level`` property can be any of `basic`, `advanced`, or `dev`.
The `dev` options are intended for use by developers, generally for
testing purposes, and are not recommended for use by operators.


Runtime Changes
===============

In most cases, Ceph permits changes to the configuration of a daemon at
runtime. This can be used for increasing or decreasing the amount of logging
output, for enabling or disabling debug settings, and for runtime optimization.

Configuration options can be updated via the ``ceph config set`` command.  For
example, to enable the debug log level on a specific OSD, run a command of this form:

.. prompt:: bash $

   ceph config set osd.123 debug_ms 20

.. note:: If an option has been customized in a local configuration file, the
   `central config
   <https://ceph.io/en/news/blog/2018/new-mimic-centralized-configuration-management/>`_
   setting will be ignored (it has a lower priority than the local
   configuration file).

Override values
---------------

Options can be set temporarily by using the `tell` or `daemon` interfaces on
the Ceph CLI. These *override* values are ephemeral, which means that they
affect only the current instance of the daemon and revert to persistently
configured values when the daemon restarts.

Override values can be set in two ways:

#. From any host, send a message to a daemon with a command of the following
   form:
   
   .. prompt:: bash $

      ceph tell <name> config set <option> <value>

   For example:
   
   .. prompt:: bash $

      ceph tell osd.123 config set debug_osd 20

   The ``tell`` command can also accept a wildcard as the daemon identifier.
   For example, to adjust the debug level on all OSD daemons, run a command of
   this form:
   
   .. prompt:: bash $

      ceph tell osd.* config set debug_osd 20

#. On the host where the daemon is running, connect to the daemon via a socket
   in ``/var/run/ceph`` by running a command of this form:

   .. prompt:: bash $

      ceph daemon <name> config set <option> <value>

   For example:
   
   .. prompt:: bash $

      ceph daemon osd.4 config set debug_osd 20

.. note:: In the output of the ``ceph config show`` command, these temporary
   values are shown with a source of ``override``.


Viewing runtime settings
========================

You can see the current options set for a running daemon with the ``ceph config show`` command.  For example:

.. prompt:: bash $

   ceph config show osd.0

will show you the (non-default) options for that daemon.  You can also look at a specific option with:

.. prompt:: bash $

   ceph config show osd.0 debug_osd

or view all options (even those with default values) with:

.. prompt:: bash $

   ceph config show-with-defaults osd.0

You can also observe settings for a running daemon by connecting to it from the local host via the admin socket.  For example:

.. prompt:: bash $

   ceph daemon osd.0 config show

will dump all current settings:

.. prompt:: bash $

   ceph daemon osd.0 config diff

will show only non-default settings (as well as where the value came from: a config file, the monitor, an override, etc.), and:

.. prompt:: bash $

   ceph daemon osd.0 config get debug_osd

will report the value of a single option.



Changes since Nautilus
======================

With the Octopus release We changed the way the configuration file is parsed.
These changes are as follows:

- Repeated configuration options are allowed, and no warnings will be printed.
  The value of the last one is used, which means that the setting last in the file
  is the one that takes effect. Before this change, we would print warning messages
  when lines with duplicated options were encountered, like::

    warning line 42: 'foo' in section 'bar' redefined

- Invalid UTF-8 options were ignored with warning messages. But since Octopus,
  they are treated as fatal errors.

- Backslash ``\`` is used as the line continuation marker to combine the next
  line with current one. Before Octopus, it was required to follow a backslash with
  a non-empty line. But in Octopus, an empty line following a backslash is now allowed.

- In the configuration file, each line specifies an individual configuration
  option. The option's name and its value are separated with ``=``, and the
  value may be quoted using single or double quotes. If an invalid
  configuration is specified, we will treat it as an invalid configuration
  file ::

    bad option ==== bad value

- Before Octopus, if no section name was specified in the configuration file,
  all options would be set as though they were within the ``global`` section. This is
  now discouraged. Since Octopus, only a single option is allowed for
  configuration files without a section name.
