Manual bootstrap of a Ceph MON on RHEL7

A Ceph MON can be created and run manually for test purposes on RHEL7 with:

$ sudo yum install ceph
$ cat > /etc/ceph/ceph.conf <<EOF
[global]
fsid = $(uuidgen)
mon_host = 127.0.0.1
auth_cluster_required = none
auth_service_required = none
auth_client_required = none
filestore_xattr_use_omap = true
EOF
$ sudo ceph-mon --cluster ceph --mkfs -i a --keyring /dev/null
ceph-mon: mon.noname-a 127.0.0.1:6789/0 is local, renaming to mon.a
ceph-mon: set fsid to 80562a76-f13e-4b1e-8fd1-de8f774f2683
ceph-mon: created monfs at /var/lib/ceph/mon/ceph-a for mon.a
$ sudo touch /var/lib/ceph/mon/ceph-a/sysvinit
$ sudo service ceph start mon.a
=== mon.a ===
Starting Ceph mon.a on mira042...
Running as unit run-7661.service.
Starting ceph-create-keys on mira042...

the cluster is not healthy because it has no OSD but it is available:

$ ceph -s
    cluster 80562a76-f13e-4b1e-8fd1-de8f774f2683
     health HEALTH_ERR 192 pgs stuck inactive; 192 pgs stuck unclean; no osds
     monmap e1: 1 mons at {a=127.0.0.1:6789/0}, election epoch 2, quorum 0 a
     osdmap e1: 0 osds: 0 up, 0 in
      pgmap v2: 192 pgs, 3 pools, 0 bytes data, 0 objects
            0 kB used, 0 kB / 0 kB avail
                 192 creating