backup.sh

#!/usr/bin/env bash

__CONFIG_FILE="/etc/backups.conf"

# A simple wrapper for a Gentoo ebuild-like `die`.
die() {
    echo "$*" 1>&2
    exit 1
}

# Source the configuration file.
[[ -f ${__CONFIG_FILE} ]] || die "Cannot find ${__CONFIG_FILE}. Exiting."
source ${__CONFIG_FILE}
# Check the required / optional variables.
[[ -z ${__BACKUP_DIR} ]] && die "__BACKUP_DIR is not set."
[[ -z ${__BACKUP_EXT} ]] && __BACKUP_EXT=".tar.gz" # default compression format
[[ -z ${__BACKUP_AGE} ]] && __BACKUP_AGE=2 # 2 day-old backups stored by default
# Set the date to be inserted to tarball names.
__DATE="$(date +%Y-%m-%d-%H-%M)"

# Wrapper around `mkdir -p`.
mkdir_p() {
    [[ ! -d "${1}" ]] && mkdir -p "${1}" && \
        echo "Created ${1} for you."
}

# Create the backup directory if it does not exist yet.
mkdir_p ${__BACKUP_DIR}

# Creates an empty tar archive. Accepts a single parameter, the filename.
empty_archive() {
    /usr/bin/env tar -cf "${1}" -T /dev/null --xattrs || \
        die "Creating ${1} failed!"
    # This works on BSD and Linux. Not tested with others.
}
# Accepts two parameters, the archive filename and the file to be added.
add_to_archive() {
    /usr/bin/env tar --xattrs --append -pf 2>/dev/null "${1}" "${2}" || \
        die "Adding ${2} to ${1} failed!"
}

clean_up() {
    /usr/bin/env find "${__BACKUP_DIR}" -ctime +${__BACKUP_AGE} -delete || \
        die "Cleanup failed!"
}

backup_docker() {
    echo "Running a Docker volumes backup..."
    if [[ -z ${__BACKUP_DIR_DOCKER} ]]; then
        __BACKUP_DIR_DOCKER=${__BACKUP_DIR}
    fi
    mkdir_p ${__BACKUP_DIR_DOCKER}
    __FILENAME="${__BACKUP_DIR_DOCKER}/${__DATE}-docker${__BACKUP_EXT}"
    # Check the presence of the Docker directory.
    [[ -d /var/lib/docker ]] || die "Docker is likely to not be installed."
    empty_archive ${__FILENAME}
    add_to_archive ${__FILENAME} /var/lib/docker/volumes
}

backup_postgres() {
    echo "Running a PostgreSQL databases backup..."
    if [[ -z ${__BACKUP_DIR_POSTGRES} ]]; then
        __BACKUP_DIR_POSTGRES=${__BACKUP_DIR}
    fi
    mkdir_p ${__BACKUP_DIR_POSTGRES}
    __FILENAME="${__BACKUP_DIR_POSTGRES}/${__DATE}-postgres${__BACKUP_EXT}"
    # The databases need to be listed in a special variable.
    [[ -z ${__BACKUP_DATABASES} ]] && die "The databases list is not specified."
    for database in "${__BACKUP_DATABASES[@]}"; do
        __DUMP_NAME="${__FILENAME}-$database"
        pg_dump -Fc $database > ${__DUMP_NAME} || \
            die "Failed backing up database $database."
        add_to_archive ${__FILENAME} ${__DUMP_NAME}
        rm ${__DUMP_NAME}
    done
}

backup_configs() {
    echo "Running config files backups..."
    if [[ -z ${__BACKUP_DIR_CONFIGS} ]]; then
        __BACKUP_DIR_CONFIGS=${__BACKUP_DIR}
    fi
    mkdir_p ${__BACKUP_DIR_CONFIGS}
    __FILENAME="${__BACKUP_DIR_CONFIGS}/${__DATE}-configs${__BACKUP_EXT}"
    # The files to be saved need to be listed in a special variable.
    [[ -z ${__BACKUP_FILES} ]] && \
        die "The files to be backed up are not specified."
    for file in "${__BACKUP_FILES[@]}"; do
        add_to_archive ${__FILENAME} $file
    done
}

print_help() {
    cat <<EOF
backup.sh: a simple backup script.

Usage:
    backup.sh [flags]

Options:
-a | --all: run the default set of backups (configs and Docker as of now)
-p | --postgres: run the backups on PostgreSQL databases
-d | --docker: run the backups on Docker volumes
-c | --configs: run the backups on the files specified in /etc/backups.conf
EOF
}

case ${1} in
    "-a" | "--all")
        backup_configs
        backup_docker
        # backup_postgres
        # This is commented out by default, as PostgreSQL backups might be
        # preferable to run under a separate user.
        ;;
    "-h" | "--help")
        print_help
        ;;
    *)
        while [[ ! -z ${1} ]]; do
            case ${1} in
                "-d" | "--docker")
                    backup_docker
                    ;;
                "-p" | "--postgres")
                    backup_postgres
                    ;;
                "-c" | "--configs")
                    backup_configs
                    ;;
            esac
            shift
        done
        ;;
esac

clean_up