backup-data

#!/bin/bash
#
# backup-data - back up data partitions using borg-backup
#
# Copyright (C) 2024 Rodrigo Silva (MestreLion) <linux@rodrigosilva.com>
# License: GPLv3 or later, at your choice. See <http://www.gnu.org/licenses/gpl>
#------------------------------------------------------------------------------
set -Eeuo pipefail  # Exit on most errors.
trap '>&2 echo "error: line $LINENO, status $?: $BASH_COMMAND"' ERR
# See https://fvue.nl/wiki/Bash:_Error_handling for caveats
#------------------------------------------------------------------------------

# TODO:
# - Consider -x | --one-file-system
# - Consider cd to _source_ instead of _repo_


# Config file location
config=${XDG_CONFIG_HOME:-$HOME/.config}/backup-data.conf

# Config arrays
declare -a options=(
	--progress
	--stats
)
declare -a excludes=(
	'lost+found'
	'.Trash*'
)

# Default archive name
default_archive='.::{now}'

#------------------------------------------------------------------------------

self="${0##*/}"

fatal()  { if (($#)); then echo "$@" >&2; usage 1 >&2; fi; }
usage()  { echo "Usage: ${self} [SOURCE_DIR [REPO_DIR [PASSWORD]]]"; exit ${1:-0}; }
exists() { type "$@" >/dev/null 2>&1; }
escape() { printf '%q' "$1"; }


#------------------------------------------------------------------------------

if ! exists borg; then
	sudo apt-get install borg
fi

if ! [[ -f "$config" ]]; then
	cat > "$config" <<-EOF
	# backup-data config file
	# Sourced by bash, mind the syntax!

	# Full path of directory to backup.
	# Mandatory, but can also be set on each run by command line argument 1.
	source=

	# Full path to backup repository (destination directory).
	# Mandatory, but can also be set by envvar BORG_REPO or command-line argument 2.
	# Will be the current directory during 'borg create' execution
	repository=

	# Repository password, if any.
	# Can also be set by envvar BORG_PASSPHRASE or command-line argument 3.
	# Leaving this blank in a password-protected repositoy will prevent
	#   non-interactive use, as borg will prompt for one.
	password=

	# Archive name. If empty will use '$default_archive' by default.
	archive=

	# Directory or device to auto-mount, usually containing the backup repository.
	# May require an entry on /etc/fstab for the device, usually with options set
	#   as 'defaults,user,noauto'.
	mount=

	# If the above mount requires sudo or not. 0 = no, 1 = yes.
	sudo_mount=1

	# 'borg create' extra options.
	# Must be a Bash array, and the following is already excluded by default:
	#	${options[@]}
	# (change '+=' to '=' in the assignment below to remove default options)
	options=(
	)

	# Extra paths to exclude from backup. Each entry will be prepended with
	#   '--exclude ' and included to 'borg create' options.
	# Since Borg 1.2.3, all paths must be relative to source directory, so
	#   do NOT use leading slashes!
	# Must be a bash array, and the following is already excluded by default:
	#	${excludes[@]}
	# (change '+=' to '=' in the assignment below to remove default excludes)
	excludes+=(
	)
	EOF
	echo "warning: config file not found, blank one created at: $config" >&2
	if [[ -t 1 ]]; then
		editor "$config"
	else
		echo "edit it and try again" >&2
		exit 1
	fi
fi

source "$config" || fatal "could not read config file: $config"

source=${source:-${1:-}}
export BORG_REPO=${2:-${BORG_REPO:-${repository:-}}}
export BORG_PASSPHRASE=${3:-${BORG_PASSPHRASE:-${password:-}}}

[[ "$source"    ]] || fatal "source directory not set"
[[ "$BORG_REPO" ]] || fatal "backup repository path not set"

archive=${archive:-$default_archive}
mount=${mount:-}
sudo_mount=${sudo_mount:-1}

for exclude in "${excludes[@]}"; do
	options+=(--exclude "$exclude")
done

if [[ "$mount" ]] && ! [[ -d "$mount" ]]; then
	if ((sudo_mount)); then sudo=sudo; else sudo=env; fi
	$sudo mount "$mount"
fi

# borg exits with code 1 on mere warnings (file permissions), 2 for actual errors
cd "$BORG_REPO" &&
echo borg create "${options[@]}" "$archive" "${source%/}"/ || (( $? >= 2 ))