Initial commit: PostgreSQL 18 slim Docker image

Alpine-based minimal PostgreSQL 18 image with multi-arch support.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: acvigue

.github/workflows/docker_image.yml

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+name: Docker Build
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    uses: acvigue/.github/.github/workflows/docker_build.yml@main

Dockerfile

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+FROM alpine:3.23
+
+ENV LANG=en_US.UTF-8 \
+    PG_MAJOR=18 \
+    PGDATA=/var/lib/postgresql/data
+
+RUN set -eux; \
+    addgroup -g 70 -S postgres; \
+    adduser -u 70 -S -D -G postgres -H -h /var/lib/postgresql -s /bin/sh postgres; \
+    mkdir -p /var/lib/postgresql; \
+    chown -R postgres:postgres /var/lib/postgresql
+
+RUN set -eux; \
+    apk add --no-cache \
+        postgresql${PG_MAJOR} \
+        postgresql${PG_MAJOR}-client \
+        su-exec \
+        tzdata \
+    ; \
+    # Remove unnecessary files
+    rm -rf \
+        /usr/share/doc \
+        /usr/share/man \
+        /var/cache/apk/* \
+    ; \
+    # Verify installation
+    postgres --version
+
+# Create required directories
+RUN mkdir -p /var/run/postgresql && chown -R postgres:postgres /var/run/postgresql && chmod 3777 /var/run/postgresql \
+    && mkdir -p "$PGDATA" && chown -R postgres:postgres "$PGDATA" && chmod 1777 "$PGDATA"
+
+COPY docker-entrypoint.sh /usr/local/bin/
+RUN chmod +x /usr/local/bin/docker-entrypoint.sh
+
+STOPSIGNAL SIGINT
+EXPOSE 5432
+
+ENTRYPOINT ["docker-entrypoint.sh"]
+CMD ["postgres"]

README.md

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+# PostgreSQL 18 Slim (Alpine)
+
+Minimal PostgreSQL 18 image for arm64/amd64. ~50MB uncompressed vs ~250MB official.
+
+## Build
+
+```bash
+# Single arch
+docker build -t postgres:18-slim .
+
+# Multi-arch
+docker buildx build --platform linux/amd64,linux/arm64 -t yourrepo/postgres:18-slim --push .
+```
+
+## Usage
+
+```bash
+# Basic
+docker run -d \
+  -e POSTGRES_PASSWORD=secret \
+  -v pgdata:/var/lib/postgresql/data \
+  postgres:18-slim
+
+# With custom db/user
+docker run -d \
+  -e POSTGRES_PASSWORD=secret \
+  -e POSTGRES_USER=myuser \
+  -e POSTGRES_DB=mydb \
+  -v pgdata:/var/lib/postgresql/data \
+  postgres:18-slim
+
+# Dev mode (no password)
+docker run -d \
+  -e POSTGRES_HOST_AUTH_METHOD=trust \
+  postgres:18-slim
+```
+
+## Environment Variables
+
+| Variable                    | Default                    | Description                                |
+| --------------------------- | -------------------------- | ------------------------------------------ |
+| `POSTGRES_PASSWORD`         | -                          | Superuser password (required unless trust) |
+| `POSTGRES_USER`             | `postgres`                 | Superuser name                             |
+| `POSTGRES_DB`               | `$POSTGRES_USER`           | Default database                           |
+| `POSTGRES_HOST_AUTH_METHOD` | -                          | Set to `trust` for no password             |
+| `PGDATA`                    | `/var/lib/postgresql/data` | Data directory                             |
+
+## Init Scripts
+
+Mount `.sh` or `.sql` files to `/docker-entrypoint-initdb.d/` for first-run initialization.
+
+## What's Removed vs Official
+
+- Locale generation (uses C.UTF-8)
+- gosu → su-exec (smaller)
+- Extensive bash scripting → sh
+- Doc/man pages
+- Contrib modules (add if needed: `postgresql18-contrib`)

docker-entrypoint.sh

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+#!/bin/sh
+set -e
+
+# Run as postgres user if started as root
+if [ "$(id -u)" = '0' ]; then
+    exec su-exec postgres "$0" "$@"
+fi
+
+# Initialize database if PGDATA is empty
+if [ "$1" = 'postgres' ] && [ -z "$(ls -A "$PGDATA" 2>/dev/null)" ]; then
+    # Set password file for initdb
+    if [ -n "$POSTGRES_PASSWORD" ]; then
+        PWFILE=$(mktemp)
+        printf '%s' "$POSTGRES_PASSWORD" > "$PWFILE"
+        INITDB_OPTS="--pwfile=$PWFILE"
+        AUTH_METHOD="scram-sha-256"
+    elif [ "${POSTGRES_HOST_AUTH_METHOD:-}" = 'trust' ]; then
+        AUTH_METHOD="trust"
+        INITDB_OPTS=""
+    else
+        echo "Error: POSTGRES_PASSWORD must be set or POSTGRES_HOST_AUTH_METHOD=trust" >&2
+        exit 1
+    fi
+
+    initdb \
+        --username="${POSTGRES_USER:-postgres}" \
+        --auth-host="$AUTH_METHOD" \
+        --auth-local="$AUTH_METHOD" \
+        $INITDB_OPTS \
+        "$PGDATA"
+
+    [ -n "${PWFILE:-}" ] && rm -f "$PWFILE"
+
+    # Configure listening
+    echo "listen_addresses = '*'" >> "$PGDATA/postgresql.conf"
+
+    # Allow connections from anywhere (container networking)
+    echo "host all all all $AUTH_METHOD" >> "$PGDATA/pg_hba.conf"
+
+    # Create additional user/database if specified
+    if [ -n "$POSTGRES_DB" ] || [ -n "$POSTGRES_USER" ]; then
+        pg_ctl -D "$PGDATA" -o "-c listen_addresses=''" -w start
+
+        if [ "$POSTGRES_DB" != 'postgres' ] && [ -n "$POSTGRES_DB" ]; then
+            psql -v ON_ERROR_STOP=1 --username "${POSTGRES_USER:-postgres}" <<-EOSQL
+                CREATE DATABASE "$POSTGRES_DB";
+EOSQL
+        fi
+
+        # Run init scripts if present
+        for f in /docker-entrypoint-initdb.d/*; do
+            case "$f" in
+                *.sh)  echo "Running $f"; . "$f" ;;
+                *.sql) echo "Running $f"; psql -v ON_ERROR_STOP=1 --username "${POSTGRES_USER:-postgres}" -f "$f" ;;
+                *)     echo "Ignoring $f" ;;
+            esac
+        done 2>/dev/null || true
+
+        pg_ctl -D "$PGDATA" -m fast -w stop
+    fi
+
+    echo "PostgreSQL init complete; ready for start up."
+fi
+
+exec "$@"