Garbage collector for Docker with Docker.

docker-gc.sh

#!/usr/bin/env bash
set -euo pipefail

# ======================================================================================================================
# Custom implementation of a garbage collector for Docker images, containers and volumes.
#
# Usage:
# bash docker-gc.sh
#
# In order to clean Docker volumes, the argument "-v" must be provided to the script.
#
# Three additional files are needed: .gc-excludes-images, .gc-excludes-containers and .gc-excludes-volumes. Those
# configuration files must be placed into the $HOME/.docker directory. They describe which elements must be preserved by
# the garbage collector. And they must contain "grep" compliant values, but can be empty as well.
# ======================================================================================================================

# Define output formats
question=$(tput bold)
warning=$(tput setaf 3)
error=$(tput setaf 1)
info=$(tput setaf 4)
success=$(tput setaf 2)
reset=$(tput sgr0)

# Check whether exclusion patterns are configured
exclude_files=("$HOME/.docker/.gc-exclude-images" "$HOME/.docker/.gc-exclude-containers" "$HOME/.docker/.gc-exclude-volumes")
for file in "${exclude_files[@]}"; do
  if [[ ! -f "${file}" ]]; then
    echo "${warning}${file} is missing, potential side-effects may occurred!${reset}"
    exit 1
  fi
done

# Request a confirmation going further
echo "This action is irreversible. Are you sure you want to continue? Only 'yes' will be accepted to approve."
read -r -p "${question}Enter a value:${reset} " response
if [[ "${response}" != "yes" ]]; then
    echo "${error}Cleaning cancelled.${reset}"
    exit 2
fi

echo ""
echo "${info}==> Cleaning containers and images...${reset}"

# Remove all unused images and containers
rm -rf /tmp/docker/spotify-gc && \
git clone git@github.com:spotify/docker-gc.git /tmp/docker/spotify-gc && \
docker build -t spotify/docker-gc /tmp/docker/spotify-gc && \
docker run --rm \
    -e "EXCLUDE_FROM_GC=$HOME/.docker/.gc-exclude-images" \
    -e "EXCLUDE_CONTAINERS_FROM_GC=$HOME/.docker/.gc-exclude-containers" \
    -v /var/run/docker.sock:/var/run/docker.sock -v /etc:/etc spotify/docker-gc

# Remove all dangling volumes
if [[ $# -eq 1 && $1 == "-v" ]]; then
    echo ""
    echo "${info}==> Cleaning volumes...${reset}"

    dangling_volumes=$(docker volume ls --quiet --filter="dangling=true" | grep -vf $HOME/.docker/.gc-exclude-volumes || true)
    if [[ ! -z ${dangling_volumes} ]]; then
        docker volume rm -f $(echo ${dangling_volumes})
    fi
fi

echo ""
echo "${success}==> Cleaning completed.${reset}"