backup.sh

#!/bin/sh

# Pull incremental backups from remote host

TIMESTAMP=$(date +%F--%H-%M-%S)

SRC_LOC="$1"
SRC_HOST="$(echo "$SRC_LOC" | cut -f 2 -d @)"
SRC_DIR="/*"
DEST_BASE="/srv/mnt/backups/incremental/$SRC_HOST"
DEST_DIR_TMP_BASE="$DEST_BASE/tmp"
DEST_DIR_TMP="$DEST_DIR_TMP_BASE/$TIMESTAMP"
DEST_DIR="$DEST_BASE/$TIMESTAMP"
RSYNC_OPTS="\
-aHAX \
--stats
--numeric-ids \
--exclude=/dev/* \
--exclude=/lost+found \
--exclude=/mnt/* \
--exclude=/proc/* \
--exclude=/run/* \
--exclude=/srv/mnt/* \
--exclude=/sys/* \
--exclude=/tmp/* \
--exclude=/var/lib/docker/overlay2/* \
--exclude=/var/lib/machines/* \
--exclude=/var/lib/nfs/rpc_pipefs/* \
--exclude=/home/*/media/* \
--exclude=/home/*/.cache/mozilla/* \
--exclude=/home/*/.cache/chromium/*\
"

# Prompt user for confirmation and read input
confirm() {
    echo -n "Proceed? [Y/n] "
    local RESPONSE=
    read -r RESPONSE
    case $RESPONSE in
        [Nn][Oo]|[Nn])
            false
            ;;
        *)
            true
            ;;
    esac
}

# Kill the script
# usage: die "$message" $status
die() {
    echo "$1" 1>&2
    exit $2
}

do_backup() {
    if [ -t 0 ]; then
        set -f
        echo running: rsync $RSYNC_OPTS $SRC_LOC:$SRC_DIR $DEST_DIR_TMP
        set +f
        confirm || die "backup aborted by user" 2
    fi

    set -f
    RSYNC_OUTPUT="$(rsync $RSYNC_OPTS $SRC_LOC:$SRC_DIR $DEST_DIR_TMP 2>&1)"
    RET="$?"
    set +f
    if [ "$RET" -ne "0" ]; then
        die "$RSYNC_OUTPUT" $RET
    fi

    mv "$DEST_DIR_TMP" "$DEST_DIR"
    if [ "$?" -ne "0" ]; then
        die "couldn't move backup $DEST_DIR_TMP to $DEST_DIR" 3
    fi

    if [ -t 0 ]; then
        echo moved backup "$DEST_DIR_TMP" to "$DEST_DIR"
        echo finished backup
    fi
}

# Find previous backup if any
find_prev_dir() {
    PREV_DIRS="$(find "$DEST_BASE" -mindepth 1 -maxdepth 1 -type d)"

    if [ "$?" -ne "0" ]; then
        die "error: failed to determine previous backup dir" 1
    fi

    if [ -n "$PREV_DIRS" ]; then
        local PREV_DIR=$(\
            echo "$PREV_DIRS" \
                | grep -E '[0-9]{4}(-[0-9]{2}){2}-(-[0-9]{2}){3}' \
                | sort -r \
                | sed -n '1 p'\
        )
        if [ -n "$PREV_DIR" ]; then
            RSYNC_OPTS="$RSYNC_OPTS --link-dest=$PREV_DIR"
        fi
    fi
}

# Make sure necessary directories are created
prep_dirs() {
    mkdir -p "$DEST_DIR_TMP_BASE"
}

prep_dirs
find_prev_dir
do_backup