# Bitnami package for Memcached

## What is Memcached?

> Memcached is an high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

[Overview of Memcached](http://memcached.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 memcached bitnami/memcached:latest
```

## Why use Bitnami Images?

* Bitnami closely tracks upstream source changes and promptly publishes new versions of this image using our automated systems.
* With Bitnami images the latest bug fixes and features are available as soon as possible.
* Bitnami containers, virtual machines and cloud images use the same components and configuration approach - making it easy to switch between formats based on your project needs.
* All our images are based on [**minideb**](https://github.com/bitnami/minideb) -a minimalist Debian based container image that gives you a small base container image and the familiarity of a leading Linux distribution- or **scratch** -an explicitly empty image-.
* All Bitnami images available in Docker Hub are signed with [Notation](https://notaryproject.dev/). [Check this post](https://blog.bitnami.com/2024/03/bitnami-packaged-containers-and-helm.html) to know how to verify the integrity of the images.
* Bitnami container images are released on a regular basis with the latest distribution packages available.

Looking to use Memcached in production? Try [VMware Tanzu Application Catalog](https://bitnami.com/enterprise), the commercial edition of the Bitnami catalog.

## How to deploy Memcached 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 Memcached Chart GitHub repository](https://github.com/bitnami/charts/tree/master/bitnami/memcached).

## 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).

## Only the latest stable branch maintained in the free Bitnami catalog

Starting December 10th, 2024, only the latest stable branch of each container image will receive updates in the free Bitnami catalog. To access up-to-date releases for all upstream-supported branches (e.g., LTS), consider upgrading to Bitnami Premium. Previously released versions will not be deleted and will remain available for pulling from DockerHub.

Please check the Bitnami Premium page in our partner [Arrow Electronics](https://www.arrow.com/globalecs/na/vendors/bitnami?utm_source=GitHub&utm_medium=containers) for more information.

## 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 repo](https://github.com/bitnami/containers).

## Get this image

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

```console
docker pull bitnami/memcached: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/memcached/tags/) in the Docker Hub Registry.

```console
docker pull bitnami/memcached:[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 .
```

## Connecting to other containers

Using [Docker container networking](https://docs.docker.com/engine/userguide/networking/), a Memcached 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.

### Using the Command Line

#### Step 1: Create a network

```console
docker network create app-tier --driver bridge
```

#### Step 2: Launch the Memcached server instance

Use the `--network app-tier` argument to the `docker run` command to attach the Memcached container to the `app-tier` network.

```console
docker run -d --name memcached-server \
    --network app-tier \
    bitnami/memcached:latest
```

#### Step 3: Launch your application container

```console
docker run -d --name myapp \
    --network app-tier \
    YOUR_APPLICATION_IMAGE
```

> **IMPORTANT**:
>
> 1. Please update the **YOUR_APPLICATION_IMAGE_** placeholder in the above snippet with your application image
> 2. In your application container, use the hostname `memcached-server` to connect to the Memcached server

### Using a Docker Compose file

When not specified, Docker Compose automatically sets up a new network and attaches all deployed services to that network. However, we will explicitly define a new `bridge` network named `app-tier`. In this example we assume that you want to connect to the Memcached server from your own custom application image which is identified in the following snippet by the service name `myapp`.

```yaml
version: '2'

networks:
  app-tier:
    driver: bridge

services:
  memcached:
    image: 'bitnami/memcached:latest'
    networks:
      - app-tier
  myapp:
    image: 'YOUR_APPLICATION_IMAGE'
    networks:
      - app-tier
```

> **IMPORTANT**:
>
> 1. Please update the **YOUR_APPLICATION_IMAGE_** placeholder in the above snippet with your application image
> 2. In your application container, use the hostname `memcached` to connect to the Memcached server

Launch the containers using:

```console
docker-compose up -d
```

## Configuration

### Environment variables

#### Customizable environment variables

| Name                        | Description                                                            | Default Value |
|-----------------------------|------------------------------------------------------------------------|---------------|
| `MEMCACHED_LISTEN_ADDRESS`  | Host that the Memcached service will bind to.                          | `nil`         |
| `MEMCACHED_PORT_NUMBER`     | Port number used by Memcached.                                         | `11211`       |
| `MEMCACHED_USERNAME`        | Memcached admin username.                                              | `root`        |
| `MEMCACHED_PASSWORD`        | Password for the Memcached admin user.                                 | `nil`         |
| `MEMCACHED_MAX_ITEM_SIZE`   | Memcached maximum item size.                                           | `nil`         |
| `MEMCACHED_EXTRA_FLAGS`     | Extra flags to be used when running Memcached.                         | `nil`         |
| `MEMCACHED_MAX_TIMEOUT`     | Maximum timeout in seconds for Memcached to start or stop.             | `5`           |
| `MEMCACHED_CACHE_SIZE`      | Memcached cache size in MB.                                            | `nil`         |
| `MEMCACHED_MAX_CONNECTIONS` | Maximum amount of concurrent connections that Memcached will tolerate. | `nil`         |
| `MEMCACHED_THREADS`         | Amount of process threads that Memcached will use.                     | `nil`         |

#### Read-only environment variables

| Name                         | Description                                 | Value                                |
|------------------------------|---------------------------------------------|--------------------------------------|
| `MEMCACHED_BASE_DIR`         | Memcached installation directory.           | `${BITNAMI_ROOT_DIR}/memcached`      |
| `MEMCACHED_CONF_DIR`         | Memcached configuration directory.          | `${MEMCACHED_BASE_DIR}/conf`         |
| `MEMCACHED_DEFAULT_CONF_DIR` | Memcached configuration directory.          | `${MEMCACHED_BASE_DIR}/conf.default` |
| `MEMCACHED_BIN_DIR`          | Memcached directory for binary executables. | `${MEMCACHED_BASE_DIR}/bin`          |
| `SASL_CONF_PATH`             | Memcached SASL configuration directory.     | `${MEMCACHED_CONF_DIR}/sasl2`        |
| `SASL_CONF_FILE`             | Memcached SASL configuration                | `${SASL_CONF_PATH}/memcached.conf`   |
| `SASL_DB_FILE`               | Memcached SASL database file.               | `${SASL_CONF_PATH}/memcachedsasldb`  |
| `MEMCACHED_DAEMON_USER`      | Memcached system user.                      | `memcached`                          |
| `MEMCACHED_DAEMON_GROUP`     | Memcached system group.                     | `memcached`                          |

### Specify the cache size

By default, the Bitnami Memcached container will not specify any cache size and will start with Memcached defaults (64MB). You can specify a different value with the `MEMCACHED_CACHE_SIZE` environment variable (in MB).

```console
docker run --name memcached -e MEMCACHED_CACHE_SIZE=128 bitnami/memcached:latest
```

or by modifying the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
services:
  memcached:
  ...
    environment:
      - MEMCACHED_CACHE_SIZE=128
  ...
```

### Specify maximum number of concurrent connections

By default, the Bitnami Memcached container will not specify any maximum number of concurrent connections and will start with Memcached defaults (1024 concurrent connections). You can specify a different value with the `MEMCACHED_MAX_CONNECTIONS` environment variable.

```console
docker run --name memcached -e MEMCACHED_MAX_CONNECTIONS=2000 bitnami/memcached:latest
```

or by modifying the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
services:
  memcached:
  ...
    environment:
      - MEMCACHED_MAX_CONNECTIONS=2000
  ...
```

### Specify number of threads to process requests

By default, the Bitnami Memcached container will not specify the amount of threads for which to process requests for and will start with Memcached defaults (4 threads). You can specify a different value with the `MEMCACHED_THREADS` environment variable.

```console
docker run --name memcached -e MEMCACHED_THREADS=4 bitnami/memcached:latest
```

or by modifying the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
services:
  memcached:
  ...
    environment:
      - MEMCACHED_THREADS=4
  ...
```

### Specify max item size (slab size)

By default, the Memcached container will not specify any max item size and will start with Memcached defaults (1048576 ~ 1 megabyte). You can specify a different value with the `MEMCACHED_MAX_ITEM_SIZE` environment variable. Only numeric values are accepted - use `8388608` instead of `8m`

```console
docker run --name memcached -e MEMCACHED_MAX_ITEM_SIZE=8388608 bitnami/memcached:latest
```

or by modifying the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
services:
  memcached:
  ...
    environment:
      - MEMCACHED_MAX_ITEM_SIZE=8388608
  ...
```

### Creating the Memcached admin user

Authentication on the Memcached server is disabled by default. To enable authentication, specify the password for the Memcached admin user using the `MEMCACHED_PASSWORD` environment variable (or in the content of the file specified in `MEMCACHED_PASSWORD_FILE`).

To customize the username of the Memcached admin user, which defaults to `root`, the `MEMCACHED_USERNAME` variable should be specified.

```console
docker run --name memcached \
  -e MEMCACHED_USERNAME=my_user \
  -e MEMCACHED_PASSWORD=my_password \
  bitnami/memcached:latest
```

or by modifying the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
version: '2'

services:
  memcached:
  ...
    environment:
      - MEMCACHED_USERNAME=my_user
      - MEMCACHED_PASSWORD=my_password
  ...
```

> The default value of the `MEMCACHED_USERNAME` is `root`.

### Passing extra command-line flags to memcached

Passing extra command-line flags to the Memcached service command is possible by adding them as arguments to *run.sh* script:

```console
docker run --name memcached bitnami/memcached:latest /opt/bitnami/scripts/memcached/run.sh -vvv
```

Alternatively, modify the [`docker-compose.yml`](https://github.com/bitnami/containers/blob/main/bitnami/memcached/docker-compose.yml) file present in this repository:

```yaml
services:
  memcached:
  ...
    command: /opt/bitnami/scripts/memcached/run.sh -vvv
  ...
```

Refer to the [Memcached man page](https://www.unix.com/man-page/linux/1/memcached/) for the complete list of arguments.

### Using custom SASL configuration

In order to load your own SASL configuration file, you will have to make them available to the container. You can do it doing the following:

* Mounting a volume with your custom configuration
* Adding custom configuration via environment variable.

By default, when authentication is enabled the SASL configuration of Memcached is written to `/opt/bitnami/memcached/sasl2/memcached.conf` file with the following content:

```config
mech_list: plain
sasldb_path: /opt/bitnami/memcached/conf/memcachedsasldb
```

The `/opt/bitnami/memcached/conf/memcachedsasldb` is the path to the sasldb file that contains the list of Memcached users.

## Logging

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

```console
docker logs memcached
```

or using Docker Compose:

```console
docker-compose logs memcached
```

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

### Upgrade this image

Bitnami provides up-to-date versions of Memcached, including security patches, soon after they are made upstream. We recommend that you follow these steps to upgrade your container.

#### Step 1: Get the updated image

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

or if you're using Docker Compose, update the value of the image property to
`bitnami/memcached:latest`.

#### Step 2: Remove the currently running container

```console
docker rm -v memcached
```

or using Docker Compose:

```console
docker-compose rm -v memcached
```

#### Step 3: Run the new image

Re-create your container from the new image.

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

or using Docker Compose:

```console
docker-compose up memcached
```

## Notable Changes

### 1.5.18-debian-9-r13 and 1.5.19-ol-7-r1

* Fixes regression in Memcached Authentication introduced in release `1.5.18-debian-9-r6` and `1.5.18-ol-7-r7` (#62).

### 1.5.18-debian-9-r6 and 1.5.18-ol-7-r7

* Decrease the size of the container. The configuration logic is now based on Bash scripts in the `rootfs/ folder.
* Custom SASL configuration should be mounted at `/opt/bitnami/memcached/conf/sasl2/` instead of `/bitnami/memcached/conf/`.
* Password for Memcached admin user can be specified in the content of the file specified in `MEMCACHED_PASSWORD_FILE`.

### 1.5.0-r1

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

### 1.4.25-r4

* `MEMCACHED_USER` parameter has been renamed to `MEMCACHED_USERNAME`.

### 1.4.25-r0

* The logs are always sent to the `stdout` and are no longer collected in the volume.

## 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/memcached).

If you detect any issue in the `docker-compose.yaml` file, feel free to report it or contribute with a fix by following our [Contributing Guidelines](https://github.com/bitnami/containers/blob/main/CONTRIBUTING.md).

## Contributing

We'd love for you to contribute to this container. You can request new features by creating an [issue](https://github.com/bitnami/containers/issues) or submitting a [pull request](https://github.com/bitnami/containers/pulls) with your contribution.

## Issues

If you encountered a problem running this container, you can file an [issue](https://github.com/bitnami/containers/issues/new/choose). For us to provide better support, be sure to fill the issue template.

## License

Copyright &copy; 2025 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.
