# Error in MongoDB backup trying to create a backup **URL:** \ **Category:** Database Monitoring and Management\ **Created:** [January 16, 2024, 2:08pm UTC](https://forums.percona.com/t/error-in-mongodb-backup-trying-to-create-a-backup/27807 "2024-01-16T14:08:21Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Enrico\_Bevilacqua](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/enrico_bevilacqua/32/14494_2.png) [@Enrico\_Bevilacqua](https://forums.percona.com/u/Enrico_Bevilacqua)\ **Post date:** [January 16, 2024, 2:08pm UTC](https://forums.percona.com/t/error-in-mongodb-backup-trying-to-create-a-backup/27807/1 "2024-01-16T14:08:21Z")
I’m trying to create a backup to do a test, one first On Demand backup on a three nodes replica set with this _Service name_: - percona-mongodb-mongodb - percona-mongodb-2-mongodb - percona-mongodb-3-mongodb It seems to me that everything in configured correctly such as: - service name, pmm agent - local path of the backup I can see in the_Create Backup on demand_ page all of three _Service name_ where I can choose from where I can create the backup. But when I click on **Backup** I get the following error: **Service percona-mongodb-mongodb must be a member of a cluster** I checked many times but the problem is still there. ---
**Author:** ![vasyl.yurkovych](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/vasyl.yurkovych/32/132_2.png) [@vasyl.yurkovych](https://forums.percona.com/u/vasyl.yurkovych)\ **Post date:** [January 24, 2024, 5:11pm UTC](https://forums.percona.com/t/error-in-mongodb-backup-trying-to-create-a-backup/27807/2 "2024-01-24T17:11:38Z")
Hi @Enrico_Bevilacqua. I think you didn’t add the --cluster flag when you were adding your mongodb instances to monitoring. We have it in our docs. Please check [here](https://docs.percona.com/percona-monitoring-and-management/get-started/backup/mongo-prerequisites.html#mongodb-backup-prerequisites) step 6