Ceph MON (CLI)

Ceph MON as static binary built
intend to use QNAP NAS Storage as a quorum/witness, generally required when a Ceph scaled-out cluster setup is running nodes in different locations

due to complexity, this is for advanced users.

ceph-mon command line is in $PATH

[~] # ceph-mon --help
usage: ceph-mon -i [flags]
--debug_mon n
debug monitor level (e.g. 10)
--mkfs
build fresh monitor fs
--force-sync
force a sync from another mon by wiping local data (BE CAREFUL)
--yes-i-really-mean-it
mandatory safeguard for --force-sync
--compact
compact the monitor store
--osdmap
only used when --mkfs is provided: load the osdmap from
--inject-monmap
write the monmap to the local monitor store and exit
--extract-monmap
extract the monmap from the local monitor store and exit
--mon-data
where the mon store and keyring are located
--set-crush-location = sets monitor's crush bucket location (only for stretch mode)
--conf/-c FILE read configuration from the given configuration file
--id/-i ID set ID portion of my name
--name/-n TYPE.ID set name
--cluster NAME set cluster name (default: ceph)
--setuser USER set uid to user or uid (and gid to user's gid)
--setgroup GROUP set gid to group or gid
--version show version and quit

--debug_ms N set message debug level (e.g. 1)


To add a MON to an existing Ceph cluster, you need to retrieve the monmap and the MON keyring from an existing Ceph node, then initialize the MON store on your MON machine. This is the official method: retrieve the monitor map and the monitor keyring, then run `ceph-mon –mkfs` with these two files.

Last update: 28 June 2026