Bug 2078902

=== 1. Bootstrap a ceph cluster.

In order to bootstrap a ceph cluster configured with multiple public networks the user has to:
1.1) prepare a ceph.conf file that contains a global section public_network for example:

[global]
public_network = 10.40.0.0/24, 10.41.0.0/24, 10.42.0.0/24

Note: At least one of the provided public networks must be configured on the current host (used for bootstrap)


1.2) bootstrap the cluster by providing this configuration file as input (using the -c argument) + any additional arguments the user wants to provide during the bootstrap:

cephadm --image <image-url> bootstrap --mon-ip <monitor-ip> -c <path-to-ceph-conf>


==== 2. Add new hosts to the subnets.

In order to add new hosts, the user has to follow the guide from:

https://docs.ceph.com/en/pacific/cephadm/host-management/#cephadm-adding-hosts

Note: the host being add must be reachable from whatever host the active mgr is running on

=== 3. Add add the networks as config for the public network param.

In a running cluster, public_network parameter could be changed by using the following cephadm command:

ceph config set mgr public_network "subnet_1,subnet_2, ..." (comma separated list of nets in subnet/mask format:10.42.0.0/24 i.e)

In case the new public networks are only available from certain hosts (and we want to move monitors to them) then the user has
to use a valid mon spec to specify the new placement.

@riv