Portainer backup to S3-compatible storage (Google Cloud Storage)

[CMircea]

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Hello!

I am trying to configure Portainer to backup to Google Cloud Storage, using the S3 interoperability.

These are my settings:
Access key ID: access key generated for the service account on the Settings -> Interoperability tab)
Secret access key: secret key from the same tab
Region: eu (region of the GCP bucket)
Bucket name: backups.example.com/portainer (name of the GCP bucket / path in the bucket)
S3 compatible host: https://storage.googleapis.com

However, I get the following error when the backup runs or I try to run it manually:

2025-04-15T05:16:32.432758297Z 2025/04/15 05:16AM ERR backup/backup.go:59 > failed to upload backup to S3 | error="failed to upload the backup: operation error S3: PutObject, https response error StatusCode: 403, RequestID: , HostID: , api error SignatureDoesNotMatch: Access denied." 
2025-04-15T05:16:32.432758297Z     at Upload (s3_client.go:55) 
2025-04-15T05:16:32.432758297Z     at BackupToS3 (backup.go:58) 
2025-04-15T05:16:32.432758297Z     at (*Handler).backupToS3 (backup.go:94) 
2025-04-15T05:16:32.432758297Z     at LoggerHandler.ServeHTTP (error.go:24) 
2025-04-15T05:16:32.432758297Z     at (*RequestBouncer).PureAdminAccess.(*RequestBouncer).mwUpgradeToRestrictedRequest.func1 (bouncer.go:404) 

I have given the service account read permissions on the bucket itself (Storage Legacy Bucket Reader) and on the folder (Storage Object Creator), but the permissions aren't the issue - I've tried to give it Bucket Owner permissions which would grant full control, but I get the same error.

I've also tried to remove the path and enter only the bucket same and removing the region, with no success.

What can I do to have Portainer backup to Google Cloud Storage?

For context, I am able to use the same configuration to backup Docker volumes using docker-volume-backup, which also supports S3-compatible storage and it works with Google Cloud Storage.

Thank you!

[jpoehnelt]

Also same error, unable to resolve, here is one of many variations I tried (changed region and bucket):