borg-reverse/backup.sh

#!/bin/bash

# Stop on any error and provide some info if DEBUG set
set -e
[ -n "$DEBUG" ] && set -x

# NOTE:
# The repo variable is used in a few different ways - it should be the name of:
# 1. an existing borg repository
# 2. a config file in $borg_dir/server_config/
# 3. an entry in your ssh config

main()
{
    local borg_old=0

    while getopts "cp:h" option; do
        case "$option" in
            c)  borg_old=1
                ;;
            p)  BORG_REPO_PATH=$OPTARG
                ;;
            h)
                display_usage 0
                ;;
            *)
                echo "Invalid option"
                display_usage 1
                ;;
        esac
    done
    shift "$((OPTIND - 1))"

    if [ $# -ne 2 ]; then
        display_usage 1
    fi
    if [ `id -u` -eq 0 ]; then
        echo "This script must not be run as root!"
        display_usage 1
    fi
    if [ -z ${BORG_REPO_PATH} ]; then
      echo "[ERROR] BORG_REPO_PATH is empty or unset."
      display_usage 1
    fi

    local mode=$1
    local repo=$2
    local borg_dir="${HOME}/.borg"

    if [ $mode != "create" ] && [ $mode != "extract" ]; then
        display_usage 1
    fi

    # Server config
    # The config file is expected to provide several arrays:
    # include, exclude and volatile
    # TODO: Move config to more standard location
    #local config_file="${borg_dir}/server_config/${repo}"
    local config_file="server_config/${repo}"
    if [[ ! -f ${config_file} ]]; then
        echo "[ERROR] Config file missing; expected ${config_file}"
        exit 1
    fi
    source "${config_file}"

    # Make sure the config defined the required arrays
    for var in include exclude; do
        if [[ -z ${!var} ]]; then
            echo "[ERROR] ${repo}: The config requires an '${var}' array"
            exit 1
        fi
    done

    # borg-backup requires --exclude to prepend each excluded item
    exclude=( "${exclude[@]/#/--exclude }" )

    ## Logging
    local log_dir="${borg_dir}/log"
    local log_month_dir=${log_dir}/$(date --utc "+%Y-%m")
    local log_file=${log_month_dir}/$(date --utc "+%Y-%m-%d_%H.%M.%SZ")_${repo}.log

    if [[ ! -d "${log_month_dir}" ]]; then
        echo "== Creating log directory"
        mkdir --parent "${log_month_dir}" \
            || { echo "[ERROR] Failed to create log directory. Aborting."; exit 1; }
    fi

    touch ${log_file} \
        || { echo "[ERROR] Failed to create log file. Aborting"; exit 1; }

    echo "== NOTE: To monitor progress, run this from another terminal:"
    echo "   $ tail -f ${log_file}"

    # Temporarilly disallow glob
    set -o noglob

    local borg_options=(--show-rc --list --stats --one-file-system --exclude-caches)

    if [[ -n $DEBUG ]]; then
        borg_options+=(--verbose)
    fi
    if [ -z $BORG_OLD ]; then
        borg_options+=(--show-version --exclude-nodump --keep-exclude-tags)
    fi

    local socket_local="/tmp/borg-local.sock"
    local socket_remote="/tmp/borg-remote.sock"

    if [ $mode == 'create' ]; then
        echo "== CREATING"
        # NOTE: "backup-server" is arbitrary and can be anything
        # the socat-wrapper will ignore it
        server_wrap $socket_local $socket_remote $mode $repo \
            borg create \
                "${borg_options[@]}" \
                "${exclude[@]}" "${volatile[@]}" \
                ssh://backup-server/$BORG_REPO_PATH/$repo::{utcnow:%Y-%m-%d} \
                "${include[@]}" \
            2>&1 | tee ${log_file}

    # TODO: Test and fix up extract procedure
    else
        echo "== EXTRACTING"
        local archive=$(borg info $BORG_REPO_PATH/$repo --last 1 | grep 'Archive name' | awk '{print $3}')
        server_wrap $socket_local $socket_remote $mode $repo \
            borg extract \
                --dry-run \
                ssh://backup-server/$BORG_REPO_PATH/$repo::$archive \
            2>&1 | tee $log_file
    fi

    # Re-allow glob
    set +o noglob

    # Tidy up
    # NOTE: socket_remote is dealt with in 'server_wrap.sh'
    if [ -f $socket_local ]; then
        rm $socket_local
    fi
}

server_wrap()
{
    if [ $# -lt 5 ]; then
        echo "[ERROR] Missing argument(s)"
        exit 1
    fi

    set -o noglob

    local socket_local="$1"
    local socket_remote="$2"
    local mode="$3"
    local repo="$4"
    local borg_command="${@:5}; rm $socket_remote"
    local remote_socat_command="'bash -c \"exec socat STDIO UNIX-CONNECT:$socket_remote\"'"

    # Make command more robust against premature expansion
    borg_command=`echo $borg_command | sed "s/--exclude\s\(\S\+\)/--exclude \'\1\'/g"`

    # TODO: Handle extract
    #if [ $mode == "extract" ]; then
    #    SH_CMD="cd /mnt"
    #fi

    exec socat UNIX-LISTEN:"$socket_local" \
        "EXEC:borg serve --append-only --restrict-to-path $BORG_REPO_PATH --umask 077" &
    ssh -t -R "$socket_remote":"$socket_local" $repo \
        sudo BORG_RSH="$remote_socat_command" "$borg_command"

    set +o noglob
}

display_usage()
{
    echo "Usage: $(basename $0) [-ch] [-p path] create|extract repo-name"
    echo "    -c    Use flags compatible with borg < (version tbd)"
    echo "    -p    Repository path. Overrides BORG_REPO_PATH"
    exit $1
}

main "$@"