Blog: customizing the docker build bake hcl file

content/authors/dchambre/index.md

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+---
+title:  Daniel Chambre
+avatar: daniel.jpg
+github: smiyc
+---
+
+A DBA and Open Source enthusiast.

content/blog/customizing-hcl/bake.hcl

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+platforms = [
+  "linux/amd64",
+]
+
+extensions = [
+  "dbgsym",
+  "partman",
+  "oracle-fdw",
+  "squeeze",
+  "show-plans",
+  "cron",
+  "tds-fdw",
+]
+
+target "myimage" {
+  dockerfile-inline = <<EOT
+ARG BASE_IMAGE="ghcr.io/cloudnative-pg/postgresql:16.9-standard-bookworm"
+FROM $BASE_IMAGE AS myimage
+ARG EXTENSIONS
+USER root
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends $EXTENSIONS \
+    ldap-utils \
+    ca-certificates \
+    openssl \
+    procps \
+    postgresql-plpython3-"${getMajor(pgVersion)}" \
+    python3-psutil \
+    pgtop \
+    pg-activity \
+    nmon \
+    libsybdb5 \
+    freetds-dev \
+    freetds-common && \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false && \
+    rm -rf /var/lib/apt/lists/* /var/cache/* /var/log/*
+RUN sed -i -e 's/# de_AT.UTF-8 UTF-8/de_AT.UTF-8 UTF-8/' /etc/locale.gen && \
+        locale-gen
+ADD https://your.git.url/postgresql/-/blob/main/.psqlrc?ref_type=heads /var/lib/postgresql/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/etc/ldap/ldap.conf?ref_type=heads /etc/ldap/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/EuropeanSSLServerCA2.crt?ref_type=heads /usr/local/share/ca-certificates/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/RootCA1v0.crt?ref_type=heads /usr/local/share/ca-certificates/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/SubCA1v1.crt?ref_type=heads /usr/local/share/ca-certificates/
+RUN update-ca-certificates 
+USER 26
+EOT
+  matrix = {
+    tgt = [
+      "myimage"
+    ]
+    pgVersion = [
+      "13.21",
+      "14.18",
+      "15.13",
+      "16.9",
+      "17.5",
+    ]
+  }
+  name = "postgresql-${index(split(".",cleanVersion(pgVersion)),0)}-standard-bookworm"
+  target = "${tgt}"
+  args = {
+    BASE_IMAGE = "ghcr.io/cloudnative-pg/postgresql:${cleanVersion(pgVersion)}-standard-bookworm",
+    EXTENSIONS = "${getExtensionsString(pgVersion, extensions)}",
+  }
+}

content/blog/customizing-hcl/index.md

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+---
+title: "Customizing the docker build bake hcl file"
+date: 2025-08-22
+draft: true
+image:
+    url: elephant_cookie.jpg
+    attribution: https://www.wallpaperflare.com/cookies-elephant-breakfast-for-children-dessert-food-sweet-food-wallpaper-asujf/download
+authors:
+ - dchambre
+tags:
+ - blog
+ - information
+ - programming
+ - applications
+ - containers
+ - postgresql
+ - postgres
+ - images
+ - tutorial
+ - bake
+ - docker
+summary: Jonathan Gonzalez wrote a guide on this blog detailing how to customize Docker images by using an override hcl file. I tried it for a spin.
+
+
+---
+
+## Summary
+
+The other week [Jonathan Gonzalez]({{% ref "/authors/jgonzalez/" %}}) wrote an 
+article on
+[how to customize docker images using an override hcl file]({{% ref "/blog/building-images-bake/" %}}).
+Before the [postgres-containers repo](https://github.com/cloudnative-pg/postgres-containers) 
+was enhanced with the option to build the images with `docker build bake`, 
+I had to follow these steps manually in order to have custom images for our workloads.
+
+- clone the repo
+- edit the dockerfile
+- build the image
+- push it to the registry
+
+Edit, build and push had to be done for each PostgreSQL version.
+So a lot of boring work needed to be done in order to have updated images.
+The chance to avoid this work sounded promising to me, so I started with the 
+[hcl file](https://raw.githubusercontent.com/cloudnative-pg/cloudnative-pg.github.io/refs/heads/main/content/blog/building-images-bake/bake.hcl) 
+Jonathan wrote, and adapted it to fit my needs.
+After a troubleshooting session with Jonathan, he asked me to share the changes I made.
+So here are my detailed instructions, in case they could prove useful to others.
+
+## Instructions
+
+### Step 1: Prepare the local Bake file
+
+To build a custom image we add the following content in a local file with name 
+`bake.hcl`:
+
+```hcl
+platforms = [
+  "linux/amd64",
+]
+
+extensions = [
+  "dbgsym",
+  "partman",
+  "oracle-fdw",
+  "squeeze",
+  "show-plans",
+  "cron",
+  "tds-fdw",
+]
+
+target "myimage" {
+  dockerfile-inline = <<EOT
+ARG BASE_IMAGE="ghcr.io/cloudnative-pg/postgresql:16.9-standard-bookworm"
+FROM $BASE_IMAGE AS myimage
+ARG EXTENSIONS
+USER root
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends $EXTENSIONS \
+    ldap-utils \
+    ca-certificates \
+    openssl \
+    procps \
+    postgresql-plpython3-"${getMajor(pgVersion)}" \
+    python3-psutil \
+    pgtop \
+    pg-activity \
+    nmon \
+    libsybdb5 \
+    freetds-dev \
+    freetds-common && \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false && \
+    rm -rf /var/lib/apt/lists/* /var/cache/* /var/log/*
+RUN sed -i -e 's/# de_AT.UTF-8 UTF-8/de_AT.UTF-8 UTF-8/' /etc/locale.gen && \
+        locale-gen
+ADD https://your.git.url/postgresql/-/blob/main/.psqlrc?ref_type=heads /var/lib/postgresql/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/etc/ldap/ldap.conf?ref_type=heads /etc/ldap/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/EuropeanSSLServerCA2.crt?ref_type=heads /usr/local/share/ca-certificates/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/RootCA1v0.crt?ref_type=heads /usr/local/share/ca-certificates/
+ADD https://your.git.url/cloudnativepg/-/blob/main/bake/files/usr/local/share/ca-certificates/SubCA1v1.crt?ref_type=heads /usr/local/share/ca-certificates/
+RUN update-ca-certificates 
+USER 26
+EOT
+  matrix = {
+    tgt = [
+      "myimage"
+    ]
+    pgVersion = [
+      "13.21",
+      "14.18",
+      "15.13",
+      "16.9",
+      "17.5",
+    ]
+  }
+  name = "postgresql-${index(split(".",cleanVersion(pgVersion)),0)}-standard-bookworm"
+  target = "${tgt}"
+  args = {
+    BASE_IMAGE = "ghcr.io/cloudnative-pg/postgresql:${cleanVersion(pgVersion)}-standard-bookworm",
+    EXTENSIONS = "${getExtensionsString(pgVersion, extensions)}",
+  }
+}
+```
+
+Starting at the beginning of the file:
+
+- The `platforms` variable is `linux/amd64` for all of my images.
+- The `extensions` variable contains some extensions I use regularly.
+- The `dockerfile-inline` part is extended with binaries, some of them are handy
+ to have, some needed by extensions or other tools I use e.g. [pgwatch](https://github.com/cybertec-postgresql/pgwatch).
+- With the `sed` command I add needed locales and build them.
+- With the `ADD` commands I extend the image with
+  - .psqlrc file, to have a nice psql Command-line even when connecting via 
+  `kubectl cnpg psql XXX`
+  - ldap.conf and the needed certs
+
+### Step 2: Build the image
+
+We can now build the image using the following command:
+
+```bash
+environment=production registry=your.repo.url docker buildx bake -f docker-bake.hcl -f cwd://bake.hcl "https://github.com/cloudnative-pg/postgres-containers.git" myimage
+```
+
+- The `environment` variable is set to `production` for all of my images, 
+because I use the same image to stage it through dev/test/prod.
+- The `registry` variable contains the repo upload url, so the images get 
+uploaded there instead of the `localhost:5000` registry used in the 
+[hcl file](https://raw.githubusercontent.com/cloudnative-pg/cloudnative-pg.github.io/refs/heads/main/content/blog/building-images-bake/bake.hcl).
+
+### Step 3: Use it
+
+The only missing step to use the images is to update your 
+[Image Catalog / Cluster Image Catalog](https://cloudnative-pg.io/documentation/current/image_catalog/) 
+with the newly built images.
+Test them and stage them through your environment.
+
+## Conclusion
+
+Once you prepare the override file to fit to your needs, the only manual steps 
+to build new images are
+
+- udpate the `pgVersion` variable
+- run the `docker buildx bake` command
+
+I hope this helps streamline your image customization process as much as it 
+did mine—feel free to build on it, and share your own improvements too! 
+You can find the supportive team in the CloudNativePG channels on the CNCF Slack workspace.