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I have deployed a ceph cluster with four node, and there are 4 mon's but i want only 3 , if I delete the 4th mon, it automatically comes back after reboot.

how do i remove it so it doesnot comes back, i am using cephadm to deploy ceph

this is the ceph mon dump output

epoch 14
fsid 383f1e64-f5a6-11ef-93f3-112a7d71c1d4
last_changed 2025-02-28T11:18:59.890169+0000
created 2025-02-28T07:34:26.733991+0000
min_mon_release 17 (quincy)
election_strategy: 1
0: [v2:10.10.20.4:3300/0,v1:10.10.20.4:6789/0] mon.ceph1
1: [v2:10.10.20.6:3300/0,v1:10.10.20.6:6789/0] mon.ceph2
2: [v2:10.10.20.5:3300/0,v1:10.10.20.5:6789/0] mon.ceph3
3: [v2:10.10.20.7:3300/0,v1:10.10.20.7:6789/0] mon.ceph4
dumped monmap epoch 14
Gerald Schneider
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biplab
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1 Answers1

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You have to edit the mon specs either directly via CLI command or via spec file. Check out the docs for more information. To get the current spec, run the following command to save the current config into file:

ceph orch ls mon --export > mon.yaml

Then remove one host from the placement and apply the file. Use the --dry-run flag to confirm your intention:

ceph orch apply -i mon.yaml --dry-run

If the result shows that one mon daemon would be removed, repeat the command with the dry-run flag.

To do the same directly via CLI command, just run:

ceph orch apply mon "host1,host2,host3"
eblock
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