How to download, edit, and upload a MON map in a Ceph cluster?

Solution Verified - Updated

Environment

  • Red Hat Ceph Storage 1.2.3

  • Red Hat Ceph Storage 1.3.x

  • Red Hat Ceph Storage 2.x

Issue

  • How to manipulate the monitor map in a Ceph cluster?

  • How to manually edit a monitor map and upload it back to the Ceph cluster?

Resolution

1.Download the monitor map using:

# ceph mon getmap -o /tmp/mon_map.bin

2.View the monitor map with:

# monmaptool --print /tmp/mon_map.bin

3.Edit the monmap with the 'monmaptool' command. In most cases, adding or removing a monitor would be the use case.

# monmaptool --rm mon_node2 /tmp/mon_map.bin

OR

# monmaptool --add mon_node /tmp/mon_map.bin
  • For more options, read the man page of 'monmaptool'. 
# man monmaptool

4.Check if the monitor map is updated with the changes

# monmaptool --print /tmp/mon_map.bin

5.Prior uploading the changed/updated monitor map, make sure that the monitor service is not running.

# service ceph stop mon

6.Upload the monitor map to the local monitor db

# ceph-mon -i <monitor_node> --inject-monmap /tmp/mon_map.bin

7.Start the mon process 

# service ceph start mon
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