backup bash script

#!/bin/bash
rootcheck () {
    if [ $(id -u) != "0" ]
    then
        echo "warning: auto appending sudo.."
        sudo "$0" "$@"
        exit $?
    fi
}
rootcheck

backup_files="{dirs to backup}"
dest="/data/backups"

now=$(date +%Y-%m-%d_%H:%M)
hostname=$(hostname)
archive_file="$hostname-$now-bak.tar.gz"

echo "backup of $backup_files => $dest/$archive_file"

tar cvzf $dest/$archive_file $backup_files 

echo "backup done. size:"
du -sh $dest/$archive_file 
ls -lh $dest