# Bitnami Secure Image for Apache ZooKeeper

> Apache ZooKeeper provides a reliable, centralized register of configuration data and services for distributed applications.

[Overview of Apache ZooKeeper](https://zookeeper.apache.org)
Trademarks: This software listing is packaged by Bitnami. The respective trademarks mentioned in the offering are owned by the respective companies, and use of them does not imply any affiliation or endorsement.

## TL;DR

```console
docker run --name zookeeper bitnami/zookeeper:latest
```

## Why use Bitnami Secure Images?

Those are hardened, minimal CVE images built and maintained by Bitnami. Bitnami Secure Images are based on the cloud-optimized, security-hardened enterprise [OS Photon Linux](https://vmware.github.io/photon/). Why choose BSI images?

- Hardened secure images of popular open source software with Near-Zero Vulnerabilities
- Vulnerability Triage & Prioritization with VEX Statements, KEV and EPSS Scores
- Compliance focus with FIPS, STIG, and air-gap options, including secure bill of materials (SBOM)
- Software supply chain provenance attestation through in-toto
- First class support for the internet’s favorite Helm charts

Each image comes with valuable security metadata. You can view the metadata in [our public catalog here](https://app-catalog.vmware.com/bitnami/apps). Note: Some data is only available with [commercial subscriptions to BSI](https://bitnami.com/).

![Alt text](https://github.com/bitnami/containers/blob/main/BSI%20UI%201.png?raw=true "Application details")
![Alt text](https://github.com/bitnami/containers/blob/main/BSI%20UI%202.png?raw=true "Packaging report")

If you are looking for our previous generation of images based on Debian Linux, please see the [Bitnami Legacy registry](https://hub.docker.com/u/bitnamilegacy).

## How to deploy Apache ZooKeeper in Kubernetes

Deploying Bitnami applications as Helm Charts is the easiest way to get started with our applications on Kubernetes. Read more about the installation in the [Bitnami Apache ZooKeeper Chart GitHub repository](https://github.com/bitnami/charts/tree/master/bitnami/zookeeper).

## Why use a non-root container?

Non-root container images add an extra layer of security and are generally recommended for production environments. However, because they run as a non-root user, privileged tasks are typically off-limits. Learn more about non-root containers [in our docs](https://techdocs.broadcom.com/us/en/vmware-tanzu/application-catalog/tanzu-application-catalog/services/tac-doc/apps-tutorials-work-with-non-root-containers-index.html).

## Supported tags and respective `Dockerfile` links

Learn more about the Bitnami tagging policy and the difference between rolling tags and immutable tags [in our documentation page](https://techdocs.broadcom.com/us/en/vmware-tanzu/application-catalog/tanzu-application-catalog/services/tac-doc/apps-tutorials-understand-rolling-tags-containers-index.html).

You can see the equivalence between the different tags by taking a look at the `tags-info.yaml` file present in the branch folder, i.e `bitnami/ASSET/BRANCH/DISTRO/tags-info.yaml`.

Subscribe to project updates by watching the [bitnami/containers GitHub repository](https://github.com/bitnami/containers).

## Get this image

The recommended way to get the Bitnami Apache ZooKeeper Docker Image is to pull the prebuilt image from the [Docker Hub Registry](https://hub.docker.com/r/bitnami/zookeeper).

```console
docker pull bitnami/zookeeper:latest
```

To use a specific version, you can pull a versioned tag. You can view the [list of available versions](https://hub.docker.com/r/bitnami/zookeeper/tags/) in the Docker Hub Registry.

```console
docker pull bitnami/zookeeper:[TAG]
```

If you wish, you can also build the image yourself by cloning the repository, changing to the directory containing the Dockerfile and executing the `docker build` command. Remember to replace the `APP`, `VERSION` and `OPERATING-SYSTEM` path placeholders in the example command below with the correct values.

```console
git clone https://github.com/bitnami/containers.git
cd bitnami/APP/VERSION/OPERATING-SYSTEM
docker build -t bitnami/APP:latest .
```

## Using `docker-compose.yaml`

Please be aware this file has not undergone internal testing. Consequently, we advise its use exclusively for development or testing purposes. For production-ready deployments, we highly recommend utilizing its associated [Bitnami Helm chart](https://github.com/bitnami/charts/tree/main/bitnami/zookeeper).

## Persisting your data

If you remove the container all your data and configurations will be lost, and the next time you run the image the database will be reinitialized. To avoid this loss of data, you should mount a volume that will persist even after the container is removed.

> **NOTE** If you have already started using Apache ZooKeeper, follow the steps on [backing up](#backing-up-your-container) and [restoring](#restoring-a-backup) to pull the data from your running container down to your host.

The image exposes a volume at `/bitnami/zookeeper` for the Apache ZooKeeper data. For persistence you can mount a directory at this location from your host. If the mounted directory is empty, it will be initialized on the first run.

> **NOTE** As this is a non-root container, the mounted files and directories must have the proper permissions for the UID `1001`.

## Connecting to other containers

Using [Docker container networking](https://docs.docker.com/engine/userguide/networking/), an Apache ZooKeeper server running inside a container can easily be accessed by your application containers.

Containers attached to the same network can communicate with each other using the container name as the hostname.

## Configuration

The following sections describe environment variables, Apache ZooKeeper configuration, security, TLS, and FIPS.

### Environment variables

You can adjust the instance using the variables below.

#### Customizable environment variables

| Name                                 | Description                                                                                                                                                                                                          | Default Value |
|--------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|
| `ZOO_DATA_LOG_DIR`                   | ZooKeeper directory where data is stored.                                                                                                                                                                            | `nil`         |
| `ZOO_PORT_NUMBER`                    | ZooKeeper client port.                                                                                                                                                                                               | `2181`        |
| `ZOO_SERVER_ID`                      | ID of the server in the ensemble.                                                                                                                                                                                    | `1`           |
| `ZOO_SERVERS`                        | Comma, space or semi-colon separated list of servers.                                                                                                                                                                | `nil`         |
| `ZOO_ENABLE_ADMIN_SERVER`            | Whether to enable the ZooKeeper admin server.                                                                                                                                                                        | `yes`         |
| `ZOO_ADMIN_SERVER_PORT_NUMBER`       | ZooKeeper admin server port.                                                                                                                                                                                         | `8080`        |
| `ZOO_PEER_TYPE`                      | Zookeeper Node Peer type                                                                                                                                                                                             | `nil`         |
| `ZOO_TICK_TIME`                      | Basic time unit in milliseconds used by ZooKeeper for heartbeats.                                                                                                                                                    | `2000`        |
| `ZOO_INIT_LIMIT`                     | ZooKeeper uses to limit the length of time the ZooKeeper servers in quorum have to connect to a leader                                                                                                               | `10`          |
| `ZOO_SYNC_LIMIT`                     | How far out of date a server can be from a leader.                                                                                                                                                                   | `5`           |
| `ZOO_MAX_CNXNS`                      | Limits the total number of concurrent connections that can be made to a ZooKeeper server. Setting it to 0 entirely removes the limit.                                                                                | `0`           |
| `ZOO_MAX_CLIENT_CNXNS`               | Limits the number of concurrent connections that a single client may make to a single member of the ZooKeeper ensemble.                                                                                              | `60`          |
| `ZOO_AUTOPURGE_INTERVAL`             | The time interval in hours for which the autopurge task is triggered. Set to a positive integer (1 and above) to enable auto purging of old snapshots and log files.                                                 | `0`           |
| `ZOO_AUTOPURGE_RETAIN_COUNT`         | When auto purging is enabled, ZooKeeper retains the most recent snapshots and the corresponding transaction logs in the dataDir and dataLogDir respectively to this number and deletes the rest. Minimum value is 3. | `3`           |
| `ZOO_LOG_LEVEL`                      | ZooKeeper log level. Available levels are: `ALL`, `DEBUG`, `INFO`, `WARN`, `ERROR`, `FATAL`, `OFF`, `TRACE`.                                                                                                         | `INFO`        |
| `ZOO_4LW_COMMANDS_WHITELIST`         | List of whitelisted 4LW commands.                                                                                                                                                                                    | `srvr, mntr`  |
| `ZOO_RECONFIG_ENABLED`               | Enable ZooKeeper Dynamic Reconfiguration.                                                                                                                                                                            | `no`          |
| `ZOO_LISTEN_ALLIPS_ENABLED`          | Listen for connections from its peers on all available IP addresses.                                                                                                                                                 | `no`          |
| `ZOO_ENABLE_PROMETHEUS_METRICS`      | Expose Prometheus metrics.                                                                                                                                                                                           | `no`          |
| `ZOO_PROMETHEUS_METRICS_PORT_NUMBER` | Port where a Jetty server will expose Prometheus metrics.                                                                                                                                                            | `7000`        |
| `ZOO_MAX_SESSION_TIMEOUT`            | Maximum session timeout in milliseconds that the server will allow the client to negotiate.                                                                                                                          | `40000`       |
| `ZOO_PRE_ALLOC_SIZE`                 | Block size for transaction log file.                                                                                                                                                                                 | `65536`       |
| `ZOO_SNAPCOUNT`                      | The number of transactions recorded in the transaction log before a snapshot can be taken (and the transaction log rolled).                                                                                          | `100000`      |
| `ZOO_HC_TIMEOUT`                     | Timeout for the Zookeeper healthcheck script (in seconds).                                                                                                                                                           | `5`           |
| `ZOO_FIPS_MODE`                      | Enable FIPS compatibility mode in ZooKeeper                                                                                                                                                                          | `yes`         |
| `ZOO_TLS_CLIENT_ENABLE`              | Enable TLS for client communication.                                                                                                                                                                                 | `false`       |
| `ZOO_TLS_PORT_NUMBER`                | Zookeeper TLS port.                                                                                                                                                                                                  | `3181`        |
| `ZOO_TLS_CLIENT_KEYSTORE_FILE`       | KeyStore file.                                                                                                                                                                                                       | `nil`         |
| `ZOO_TLS_CLIENT_KEYSTORE_TYPE`       | KeyStore file type.                                                                                                                                                                                                  | `nil`         |
| `ZOO_TLS_CLIENT_KEYSTORE_PASSWORD`   | KeyStore file password.                                                                                                                                                                                              | `nil`         |
| `ZOO_TLS_CLIENT_TRUSTSTORE_FILE`     | TrustStore file.                                                                                                                                                                                                     | `nil`         |
| `ZOO_TLS_CLIENT_TRUSTSTORE_TYPE`     | TrustStore file type.                                                                                                                                                                                                | `nil`         |
| `ZOO_TLS_CLIENT_TRUSTSTORE_PASSWORD` | TrustStore file password.                                                                                                                                                                                            | `nil`         |
| `ZOO_TLS_CLIENT_AUTH`                | Specifies options to authenticate TLS connections from clients. Available values are: `none`, `want`, `need`.                                                                                                        | `need`        |
| `ZOO_TLS_QUORUM_ENABLE`              | Enable TLS for quorum communication.                                                                                                                                                                                 | `false`       |
| `ZOO_TLS_QUORUM_KEYSTORE_FILE`       | KeyStore file.                                                                                                                                                                                                       | `nil`         |
| `ZOO_TLS_QUORUM_KEYSTORE_TYPE`       | KeyStore file type.                                                                                                                                                                                                  | `nil`         |
| `ZOO_TLS_QUORUM_KEYSTORE_PASSWORD`   | KeyStore file password.                                                                                                                                                                                              | `nil`         |
| `ZOO_TLS_QUORUM_TRUSTSTORE_FILE`     | TrustStore file.                                                                                                                                                                                                     | `nil`         |
| `ZOO_TLS_QUORUM_TRUSTSTORE_TYPE`     | TrustStore file type.                                                                                                                                                                                                | `nil`         |
| `ZOO_TLS_QUORUM_TRUSTSTORE_PASSWORD` | TrustStore file password.                                                                                                                                                                                            | `nil`         |
| `ZOO_TLS_QUORUM_CLIENT_AUTH`         | Specifies options to authenticate TLS connections from clients. Available values are: `none`, `want`, `need`.                                                                                                        | `need`        |
| `JVMFLAGS`                           | Default JVMFLAGS for the ZooKeeper process.                                                                                                                                                                          | `nil`         |
| `ZOO_HEAP_SIZE`                      | Size in MB for the Java Heap options (Xmx and XMs). This env var is ignored if Xmx an Xms are configured via `JVMFLAGS`.                                                                                             | `1024`        |
| `ZOO_ENABLE_AUTH`                    | Enable ZooKeeper auth. It uses SASL/Digest-MD5.                                                                                                                                                                      | `no`          |
| `ZOO_CLIENT_USER`                    | User that will use ZooKeeper clients to auth.                                                                                                                                                                        | `nil`         |
| `ZOO_SERVER_USERS`                   | Comma, semicolon or whitespace separated list of user to be created.                                                                                                                                                 | `nil`         |
| `ZOO_CLIENT_PASSWORD`                | Password that will use ZooKeeper clients to auth.                                                                                                                                                                    | `nil`         |
| `ZOO_SERVER_PASSWORDS`               | Comma, semicolon or whitespace separated list of passwords to assign to users when created. Example: `pass4user1, pass4user2, pass4admin`.                                                                           | `nil`         |
| `ZOO_ENABLE_QUORUM_AUTH`             | Enable ZooKeeper auth. It uses SASL/Digest-MD5.                                                                                                                                                                      | `no`          |
| `ZOO_QUORUM_LEARNER_USER`            | User that will be used by the ZooKeeper Quorum Learner to auth with Quorum Servers.                                                                                                                                  | `nil`         |
| `ZOO_QUORUM_LEARNER_PASSWORD`        | Password that will use ZooKeeper Quorum Learner to auth.                                                                                                                                                             | `nil`         |
| `ZOO_QUORUM_SERVER_USERS`            | Comma, semicolon or whitespace separated list of quorum users to be created.                                                                                                                                         | `nil`         |
| `ZOO_QUORUM_SERVER_PASSWORDS`        | Comma, semicolon or whitespace separated list of passwords to assign to quorum users when created. Example: `pass4user1, pass4user2, pass4admin`.                                                                    | `nil`         |

#### Read-only environment variables

| Name                   | Description                                 | Value                           |
|------------------------|---------------------------------------------|---------------------------------|
| `ZOO_BASE_DIR`         | ZooKeeper installation directory.           | `${BITNAMI_ROOT_DIR}/zookeeper` |
| `ZOO_VOLUME_DIR`       | ZooKeeper persistence directory.            | `/bitnami/zookeeper`            |
| `ZOO_DATA_DIR`         | ZooKeeper directory where data is stored.   | `${ZOO_VOLUME_DIR}/data`        |
| `ZOO_CONF_DIR`         | ZooKeeper configuration directory.          | `${ZOO_BASE_DIR}/conf`          |
| `ZOO_DEFAULT_CONF_DIR` | ZooKeeper default configuration directory.  | `${ZOO_BASE_DIR}/conf.default`  |
| `ZOO_CONF_FILE`        | ZooKeeper configuration file.               | `${ZOO_CONF_DIR}/zoo.cfg`       |
| `ZOO_LOG_DIR`          | Directory where ZooKeeper logs are stored.  | `${ZOO_BASE_DIR}/logs`          |
| `ZOO_LOG_FILE`         | Directory where ZooKeeper logs are stored.  | `${ZOO_LOG_DIR}/zookeeper.out`  |
| `ZOO_BIN_DIR`          | ZooKeeper directory for binary executables. | `${ZOO_BASE_DIR}/bin`           |
| `ZOO_DAEMON_USER`      | ZooKeeper system user.                      | `zookeeper`                     |
| `ZOO_DAEMON_GROUP`     | ZooKeeper system group.                     | `zookeeper`                     |

When you start the Apache ZooKeeper image, you can adjust the configuration of the instance by passing one or more environment variables either on the docker-compose file or on the `docker run` command line. If you want to add a new environment variable:

- For manual execution add a -e option with each variable and value:

```console
docker run --name zookeeper -e ZOO_SERVER_ID=1 bitnami/zookeeper:latest
```

- For docker-compose add the variable name and value under the application section in the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/zookeeper/docker-compose.yml) file present in this repository:

```yaml
services:
  zookeeper:
  ...
    environment:
      - ZOO_SERVER_ID=1
  ...
```

### Apache ZooKeeper configuration

The image looks for configuration in the `conf/` directory of `/opt/bitnami/zookeeper`.

### Security

Authentication based on SASL/Digest-MD5 can be easily enabled by passing the `ZOO_ENABLE_AUTH` environment variable.
When enabling the Apache ZooKeeper authentication, it is also required to pass the list of users and passwords that will
be able to login.

> **NOTE** Authentication is enabled using the CLI tool `zkCli.sh`. Therefore, it's necessary to set `ZOO_CLIENT_USER` and `ZOO_CLIENT_PASSWORD` environment variables too.

As SASL/Digest-MD5 is not compatible with FIPS, it's mandatory to disable "fips-mode" in Apache ZooKeeper.

> **NOTE** If fips-mode is required in your environment, you should deploy Apache ZooKeeper using a different auth mechanism like TLS.

### Start Apache ZooKeeper with TLS

The Apache ZooKeeper container can be setup to serve clients securely via TLS. To do so, enable the `ZOO_TLS_CLIENT_ENABLE` environment variable.

The keystore and truststore can be mounted in the `/bitnami/zookeeper/certs` directory. Note that the environment variables `ZOO_TLS_CLIENT_KEYSTORE_FILE` or `ZOO_TLS_CLIENT_TRUSTSTORE_FILE` define the location of the mounted certificates.

Run the image with TLS enabled as follows.

```console
docker run --name zookeeper \
  -v /path/to/zookeeper.keystore.jks:/bitnami/zookeeper/certs/zookeeper.keystore.jks:ro
  -v /path/to/zookeeper.truststore.jks:/bitnami/zookeeper/certs/zookeeper.truststore.jks:ro
  -e ZOO_TLS_CLIENT_ENABLE=yes \
  -e ZOO_TLS_CLIENT_KEYSTORE_FILE=/bitnami/zookeeper/certs/zookeeper.keystore.jks \
  -e ZOO_TLS_CLIENT_TRUSTSTORE_FILE=/bitnami/zookeeper/certs/zookeeper.truststore.jks \
  bitnami/zookeeper:latest
```

### Setting up an Apache ZooKeeper ensemble

An Apache ZooKeeper (<https://zookeeper.apache.org/doc/r3.1.2/zookeeperAdmin.html>) cluster can easily be setup with the Bitnami Apache ZooKeeper Docker image using the following environment variables:

- `ZOO_SERVERS`: Comma, space or semi-colon separated list of servers. This can be done with or without specifying the ID of the server in the ensemble. No defaults. Examples:
- without Server ID - zoo1:2888:3888,zoo2:2888:3888
- with Server ID - zoo1:2888:3888::1,zoo2:2888:3888::2
- without Server ID and Observers - zoo1:2888:3888,zoo2:2888:3888:observer
- with Server ID and Observers - zoo1:2888:3888::1,zoo2:2888:3888:observer::2

For reliable Apache ZooKeeper service, you should deploy Apache ZooKeeper in a cluster known as an ensemble. As long as a majority of the ensemble are up, the service will be available. Because Apache ZooKeeper requires a majority, it is best to use an odd number of machines. For example, with four machines Apache ZooKeeper can only handle the failure of a single machine; if two machines fail, the remaining two machines do not constitute a majority. However, with five machines Apache ZooKeeper can handle the failure of two machines.

You have to use 0.0.0.0 as the host for the server. More concretely, if the ID of the zookeeper1 container starting is 1, then the ZOO_SERVERS environment variable has to be 0.0.0.0:2888:3888,zookeeper2:2888:3888,zookeeper3:2888:3888 or if the ID of zookeeper servers are non-sequential then they need to be specified 0.0.0.0:2888:3888::2,zookeeper2:2888:3888::4.zookeeper3:2888:3888::6

### FIPS configuration in Bitnami Secure Images

The Bitnami Apache ZooKeeper Docker image from the [Bitnami Secure Images](https://go-vmware.broadcom.com/contact-us) catalog includes extra features and settings to configure the container with FIPS capabilities. You can configure the next environment variables:

- `OPENSSL_FIPS`: whether OpenSSL runs in FIPS mode or not. `yes` (default), `no`.

## Logging

The Bitnami Apache ZooKeeper Docker image sends the container logs to the `stdout`. To view the logs:

```console
docker logs zookeeper
```

or using Docker Compose:

```console
docker-compose logs zookeeper
```

You can configure the containers [logging driver](https://docs.docker.com/engine/admin/logging/overview/) using the `--log-driver` option if you wish to consume the container logs differently. In the default configuration docker uses the `json-file` driver.

## Maintenance

The following sections describe how to back up, restore, and upgrade the container.

### Backing up your container

To backup your data, follow these simple steps:

#### Step 1: Stop the currently running container

```console
docker stop zookeeper
```

or using Docker Compose:

```console
docker-compose stop zookeeper
```

#### Step 2: Run the backup command

We need to mount two volumes in a container we will use to create the backup: a directory on your host to store the backup in, and the volumes from the container we just stopped so we can access the data.

```console
docker run --rm -v /path/to/zookeeper-backups:/backups --volumes-from zookeeper busybox \
  cp -a /bitnami/zookeeper /backups/latest
```

or using Docker Compose:

```console
docker run --rm -v /path/to/zookeeper-backups:/backups --volumes-from `docker-compose ps -q zookeeper` busybox \
  cp -a /bitnami/zookeeper /backups/latest
```

### Restoring a backup

Restoring a backup is as simple as mounting the backup as volumes in the container.

```console
docker run -v /path/to/zookeeper-backups/latest:/bitnami/zookeeper bitnami/zookeeper:latest
```

or using Docker Compose:

```yaml
version: '2'

services:
  zookeeper:
    image: bitnami/zookeeper:latest
    ports:
      - 2181:2181
    volumes:
      - /path/to/zookeeper-backups/latest:/bitnami/zookeeper
```

## Notable changes

The following subsections describe notable changes.

### 3.5.5-r95

- Apache ZooKeeper configuration moved to bash scripts in the rootfs/ folder.

### 3.4.12-r25

- Configuration is not persisted, it is regenerated each time the container is created or it is used as volume.

### 3.4.10-r4

- The zookeeper container has been migrated to a non-root container approach. Previously the container run as `root` user and the zookeeper daemon was started as `zookeeper` user. From now on, both the container and the zookeeper daemon run as user `1001`.
  As a consequence, the configuration files are writable by the user running the zookeeper process.

### 3.4.10-r0

- New release

## License

Copyright &copy; 2026 Broadcom. The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

<http://www.apache.org/licenses/LICENSE-2.0>

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
