Cephadm Concepts
================
-.. _cephadm-fqdn:
-
-Fully qualified domain names vs bare host names
------------------------------------------------
-
-cephadm has very minimal requirements when it comes to resolving host
-names etc. When cephadm initiates an ssh connection to a remote host,
-the host name can be resolved in four different ways:
-
-- a custom ssh config resolving the name to an IP
-- via an externally maintained ``/etc/hosts``
-- via explicitly providing an IP address to cephadm: ``ceph orch host add <hostname> <IP>``
-- automatic name resolution via DNS.
-
-Ceph itself uses the command ``hostname`` to determine the name of the
-current host.
-
-.. note::
-
- cephadm demands that the name of the host given via ``ceph orch host add``
- equals the output of ``hostname`` on remote hosts.
-
-Otherwise cephadm can't be sure, the host names returned by
-``ceph * metadata`` match the hosts known to cephadm. This might result
-in a :ref:`cephadm-stray-host` warning.
-
-When configuring new hosts, there are two **valid** ways to set the
-``hostname`` of a host:
-
-1. Using the bare host name. In this case:
-
-- ``hostname`` returns the bare host name.
-- ``hostname -f`` returns the FQDN.
-
-2. Using the fully qualified domain name as the host name. In this case:
-
-- ``hostname`` returns the FQDN
-- ``hostname -s`` return the bare host name
-
-Note that ``man hostname`` recommends ``hostname`` to return the bare
-host name:
-
- The FQDN (Fully Qualified Domain Name) of the system is the
- name that the resolver(3) returns for the host name, such as,
- ursula.example.com. It is usually the hostname followed by the DNS
- domain name (the part after the first dot). You can check the FQDN
- using ``hostname --fqdn`` or the domain name using ``dnsdomainname``.
-
- .. code-block:: none
-
- You cannot change the FQDN with hostname or dnsdomainname.
-
- The recommended method of setting the FQDN is to make the hostname
- be an alias for the fully qualified name using /etc/hosts, DNS, or
- NIS. For example, if the hostname was "ursula", one might have
- a line in /etc/hosts which reads
-
- 127.0.1.1 ursula.example.com ursula
-
-Which means, ``man hostname`` recommends ``hostname`` to return the bare
-host name. This in turn means that Ceph will return the bare host names
-when executing ``ceph * metadata``. This in turn means cephadm also
-requires the bare host name when adding a host to the cluster:
-``ceph orch host add <bare-name>``.
-
-..
- TODO: This chapter needs to provide way for users to configure
- Grafana in the dashboard, as this is right no very hard to do.
Cephadm Scheduler
-----------------
manually distributed to the mgr data directory
(``/var/lib/ceph/<cluster-fsid>/mgr.<id>`` on the host, visible at
``/var/lib/ceph/mgr/ceph-<id>`` from inside the container).
+
+.. _cephadm-fqdn:
+
+Fully qualified domain names vs bare host names
+===============================================
+
+cephadm has very minimal requirements when it comes to resolving host
+names etc. When cephadm initiates an ssh connection to a remote host,
+the host name can be resolved in four different ways:
+
+- a custom ssh config resolving the name to an IP
+- via an externally maintained ``/etc/hosts``
+- via explicitly providing an IP address to cephadm: ``ceph orch host add <hostname> <IP>``
+- automatic name resolution via DNS.
+
+Ceph itself uses the command ``hostname`` to determine the name of the
+current host.
+
+.. note::
+
+ cephadm demands that the name of the host given via ``ceph orch host add``
+ equals the output of ``hostname`` on remote hosts.
+
+Otherwise cephadm can't be sure, the host names returned by
+``ceph * metadata`` match the hosts known to cephadm. This might result
+in a :ref:`cephadm-stray-host` warning.
+
+When configuring new hosts, there are two **valid** ways to set the
+``hostname`` of a host:
+
+1. Using the bare host name. In this case:
+
+- ``hostname`` returns the bare host name.
+- ``hostname -f`` returns the FQDN.
+
+2. Using the fully qualified domain name as the host name. In this case:
+
+- ``hostname`` returns the FQDN
+- ``hostname -s`` return the bare host name
+
+Note that ``man hostname`` recommends ``hostname`` to return the bare
+host name:
+
+ The FQDN (Fully Qualified Domain Name) of the system is the
+ name that the resolver(3) returns for the host name, such as,
+ ursula.example.com. It is usually the hostname followed by the DNS
+ domain name (the part after the first dot). You can check the FQDN
+ using ``hostname --fqdn`` or the domain name using ``dnsdomainname``.
+
+ .. code-block:: none
+
+ You cannot change the FQDN with hostname or dnsdomainname.
+
+ The recommended method of setting the FQDN is to make the hostname
+ be an alias for the fully qualified name using /etc/hosts, DNS, or
+ NIS. For example, if the hostname was "ursula", one might have
+ a line in /etc/hosts which reads
+
+ 127.0.1.1 ursula.example.com ursula
+
+Which means, ``man hostname`` recommends ``hostname`` to return the bare
+host name. This in turn means that Ceph will return the bare host names
+when executing ``ceph * metadata``. This in turn means cephadm also
+requires the bare host name when adding a host to the cluster:
+``ceph orch host add <bare-name>``.
+
+..
+ TODO: This chapter needs to provide way for users to configure
+ Grafana in the dashboard, as this is right no very hard to do.
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