CEPH-MON(8) Ceph CEPH-MON(8)

# [NAME](#NAME)

ceph-mon - ceph monitor daemon

# [SYNOPSIS](#SYNOPSIS)

```
ceph-mon -i monid [ --mon-data mondatapath ]
```

# [DESCRIPTION](#DESCRIPTION)

**ceph-mon** is the cluster monitor daemon for the Ceph distributed file system. One or more instances of **ceph-mon** form a Paxos part-time parliament cluster that provides extremely reliable and durable storage of cluster membership, configuration, and state.

The *mondatapath* refers to a directory on a local file system storing monitor data. It is normally specified via the **mon data** option in the configuration file.

# [OPTIONS](#OPTIONS)

[**-f, --foreground**](#f,)

Foreground: do not daemonize after startup (run in foreground). Do not generate a pid file. Useful when run via ceph-run <>(8).

[**-d**](#d)

Debug mode: like **-f**, but also send all log output to stderr.

[**--setuser userorgid**](#setuser)

Set uid after starting. If a username is specified, the user record is looked up to get a uid and a gid, and the gid is also set as well, unless --setgroup is also specified.

[**--setgroup grouporgid**](#setgroup)

Set gid after starting. If a group name is specified the group record is looked up to get a gid.

[**-c ceph.conf, --conf=ceph.conf**](#c)

Use *ceph.conf* configuration file instead of the default **/etc/ceph/ceph.conf** to determine monitor addresses during startup.

[**--mkfs**](#mkfs)

Initialize the **mon data** directory with seed information to form and initial ceph file system or to join an existing monitor cluster. Three pieces of information must be provided:

- The cluster fsid. This can come from a monmap (**--monmap <path>**) or explicitly via **--fsid <uuid>**.
- A list of monitors and their addresses. This list of monitors can come from a monmap (**--monmap <path>**), the **mon host** configuration value (in *ceph.conf* or via **-m** **host1,host2,...**), or (for backward compatibility) the deprecated **mon addr** lines in *ceph.conf*. If this monitor is to be part of the initial monitor quorum for a new Ceph cluster, then it must be included in the initial list, matching either the name or address of a monitor in the list. When matching by address, either the **public addr** or **public** **subnet** options may be used.
- The monitor secret key **mon.**. This must be included in the keyring provided via **--keyring <path>**.

[**--keyring**](#keyring)

Specify a keyring for use with **--mkfs**.

[**--use-mon-keyring**](#use)

Use the mon's keyring file as authoritative for the "mon." secret. Normally the key in the mons' auth database is used.

[**--no-config-file**](#no)

Signal that we don't want to rely on a *ceph.conf*, either user provided or the default, to run the daemon. This will entail providing all necessary options to the daemon as arguments.

# [AVAILABILITY](#AVAILABILITY)

**ceph-mon** is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at <https://docs.ceph.com> for more information.

# [SEE ALSO](#SEE_ALSO)

ceph <>(8), ceph-mds <>(8), ceph-osd <>(8)

# [Copyright](#Copyright)

2010-2014, Inktank Storage, Inc. and contributors. Licensed under Creative Commons Attribution Share Alike 3.0 (CC-BY-SA-3.0)

October 16, 2026 dev

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Document: ceph-mon(8) from ceph-20 20.2.4-r8 (Chainguard OS)
Source: https://github.com/ceph/ceph.git