Failing to Backup ClickHouse Database: Authentication Failed

[m-mattia-m]

I've set up a ClickHouse database using the Bitnami Helm Chart. For backup purposes, I added the altinity/clickhouse-backup tool. Initially, I created a CronJob to perform the backups but later realized that it needs to run within the same Pod as the database.

To address this, I added the backup tool as a sidecar container to the ClickHouse Pod. However, I'm encountering an authentication failure when the backup container tries to connect to the database.

Interestingly, if I forward the port to my local machine, I can successfully log in using the same username and password:

Is there anything I'm missing in my setup?

kubectl -n plausible port-forward svc/plausible-clickhouse 8123:8123

Here is my relevant values.yaml configuration:

clickhouse:
  image:
  shards: 1
  replicaCount: 1
  keeper:
    replicaCount: 1
  auth:
    enabled: true
    username: "plausible"
    existingSecret: "plausible-db-clickhouse-credentials"
    existingSecretKey: "password"
  persistence:
    enabled: true
    storageClass: "csi-cinder-sc-retain"
    size: "8Gi"
  initdbScripts:
    db-init.sql: |
      CREATE DATABASE IF NOT EXISTS plausible_events
  sidecars:
    - name: backup
      image: ghcr.io/altinity/clickhouse-backup:2.6.32
      env:
        - name: LOG_LEVEL
          value: debug
        - name: CLICKHOUSE_HOST
          value: "localhost"
        - name: CLICKHOUSE_PORT
          value: "9000"
        - name: CLICKHOUSE_USER
          value: plausible
        - name: CLICKHOUSE_PASSWORD
          valueFrom:
            secretKeyRef:
              name: plausible-db-clickhouse-credentials
              key: password
        - name: CONFIG_FILE
          value: ""
        - name: S3_ENDPOINT
          value: "https://sos-ch-gva-2.exo.io"
        - name: S3_BUCKET
          value: "c01-database-backup"
        - name: S3_PREFIX
          value: "clickhouse/plausible"
        - name: CLICKHOUSE_BACKUP_S3_ACCESS_KEY
          valueFrom:
            secretKeyRef:
              name: s3-credentials
              key: accessKeyId
        - name: CLICKHOUSE_BACKUP_S3_SECRET_KEY
          valueFrom:
            secretKeyRef:
              name: s3-credentials
              key: secretAccessKey
        - name: CLICKHOUSE_BACKUP_S3_REGION
          value: "ch-gva-2"
      volumeMounts:
        - mountPath: /bitnami/clickhouse
          name: data

Here is the error I'm facing:

:/# clickhouse-backup create_remote
2025-08-07 14:37:35.131 INF pkg/clickhouse/clickhouse.go:131 > clickhouse connection prepared: tcp://localhost:9000 run ping
2025-08-07 14:37:35.133 WRN pkg/clickhouse/clickhouse.go:141 > clickhouse connection ping: tcp://localhost:9000 return error: code: 516, message: default: Authentication failed: password is incorrect, or there is no user with such name.

If you use ClickHouse Cloud, the password can be reset at https://clickhouse.cloud/
on the settings page for the corresponding service.

If you have installed ClickHouse and forgot password you can reset it in the configuration file.
The password for default user is typically located at /etc/clickhouse-server/users.d/default-password.xml
and deleting this file will reset the password.
See also /etc/clickhouse-server/users.xml on the server where ClickHouse is installed., will wait 5 second to reconnect

[Slach]

user CLICKHOUSE_USERNAME instead of CLICKHOUSE_USER you tried to connect with default user

[m-mattia-m]

What a silly mistake I made! This worked — thank you very much.