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monmaptool - ceph monitor cluster map manipulation tool


monmaptool <action> [options] mapfilename


monmaptool is a utility to create, view, and modify a monitor cluster map for the Ceph distributed storage system. The monitor map specifies the only fixed addresses in the Ceph distributed system. All other daemons bind to arbitrary addresses and register themselves with the monitors.

When creating a map with --create, a new monitor map with a new, random UUID will be created. It should be followed by one or more monitor addresses.

The default Ceph monitor port for messenger protocol v1 is 6789, and 3300 for protocol v2.

Multiple actions can be performed per invocation.


print a plaintext dump of the map, after any modifications are made.

list the enabled features as well as the available ones.

By default, a human readable output is produced.

create a new monitor map with a new UUID (and with it, a new, empty Ceph cluster).

allow monmaptool to create a new mapfilename in place of an existing map.

Only useful when --create is used.

generate a new monmap based on the values on the command line or specified in the ceph configuration. This is, in order of preference,
--monmap filename to specify a monmap to load
--mon-host 'host1,ip2' to specify a list of hosts or ip addresses
[] sections containing mon addr settings in the config. Note that this method is not recommended and support will be removed in a future release.

filter the initial monmap by applying the mon initial members setting. Monitors not present in that list will be removed, and initial members not present in the map will be added with dummy addresses.

add a monitor with the specified ip:port to the map.

If the nautilus feature is set, and the port is not, the monitor will be added for both messenger protocols.

add a monitor with the specified version:ip:port to the map.

remove the monitor with the specified name from the map.

set the fsid to the given uuid. If not specified with --create, a random fsid will be generated.

enable all supported features.

set the min_mon_release.


To create a new map with three monitors (for a fresh Ceph cluster):

monmaptool --create --add nodeA --add nodeB \

--add nodeC --enable-all-features --clobber monmap

To display the contents of the map:

monmaptool --print monmap

To replace one monitor:

monmaptool --rm nodeA monmap
monmaptool --add nodeA monmap


monmaptool is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at for more information.


ceph(8), crushtool(8),


2010-2024, Inktank Storage, Inc. and contributors. Licensed under Creative Commons Attribution Share Alike 3.0 (CC-BY-SA-3.0)

April 26, 2024 dev