Backups. No one likes doing them, but they’re too important not to do. Typically when I’m doing stuff for my websites, I will occasionally do a tar of a directory and save it off, or even set up a script that will do this nightly. Then I have issues with disks filling up, and not wanting to delete my backups for fear of losing something (like the 20 copies aren’t enough!)

Recently, I decided to put an end to my backup worries, and write a differential backup system. What is a differential backup? Go go gadget Wikipedia! Basically, a differential backup means that I won’t be filling up my drives any time soon, because I’m not doing a FULL backup each time — it’s only backing up the changes that have been made since the last full backup, which runs weekly and monthly. I’ve been running and tuning the script for a while, and wanted to make sure that it’s working properly. If you decide to use this script, you MUST test the restores with it, as I can’t be responsible if you lose data and the script somehow fails you. You have been warned! Without further ado, the script:

#!/usr/bin/perl
# Website Differential Backup
# Keeps several websites and their databases backed up
# by Ed Salisbury (ed@edsalisbury.net)
# http://www.edsalisbury.net
# (c)2009 Ed Salisbury, Some Rights Reserved
#
# Config File Format
# DIR /path/to/dir
# DB dbname
#
# Limitations:
# * Cannot do differential backups of databases
#
#
# License:
# Except where otherwise noted, this work is licensed under Creative Commons
#   Attribution ShareAlike 3.0.
#
# You are free:
#   * to Share - to copy, distribute and transmit the work
#   * to Remix - to adapt the work
#
# Under the following conditions:
#   * Attribution. You must attribute the work in the manner specified by the
#     author or licensor (but not in any way that suggests that they endorse
#     you or your use of the work).
#   * Share Alike. If you alter, transform, or build upon this work, you may
#     distribute the resulting work only under the same, similar or a
#     compatible license.
#   * For any reuse or distribution, you must make clear to others the license
#     terms of this work. The best way to do this is with a link to the
#     license's web page (http://creativecommons.org/licenses/by-sa/3.0/)
#   * Any of the above conditions can be waived if you get permission from the
#   * Nothing in this license impairs or restricts the author's moral rights.

use strict;
use warnings;

# Place to store backups
my $BACKUP_DIR = "/backup";
# Configuration file to read what to backup
my $BACKUP_CONF = "/usr/local/etc/backup.conf";
# Database user/pass
my $DB_USER = 'root';
my $DB_PASS = '**DBPASSWD**';

# Turn off output buffering
$|++;

# Tools
my $TAR = '/bin/tar';
my $GZIP = '/bin/gzip';
my $LS = '/bin/ls';
my $HEAD = '/usr/bin/head';
my $MKDIR = '/bin/mkdir';
my $RM = '/bin/rm';
my $MYSQLDUMP = '/usr/local/mysql/bin/mysqldump';

my @months = qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec );
my @days = qw( Sun Mon Tue Wed Thu Fri Sat );
my @dirs;
my @dbs;

# Get current date
my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst) = localtime time;
my $datestamp = sprintf("%04d%02d%02d", $year+1900, $mon+1, $mday);
my $day = $days[$wday];

# Read config file
unless (open(CFG, $BACKUP_CONF))
{
    print "Error: Cannot open $BACKUP_CONFn";
    exit(1);
}
while (<CFG>)
{
    chomp;
    if (/^DIRs+(.*)$/i)
    {
        push (@dirs, $1);
    }
    elsif (/^DBs+(.*)$/i)
    {
        push (@dbs, $1);
    }
}
close (CFG);

# Do Directory Backups
foreach my $dir (@dirs)
{
    print "Backing up $dir... ";

    # Add backslashes for spaces
    $dir =~ s/ /\ /g;

    my $backup_src = $dir;

    # Convert slashes to underscores
    $dir =~ s///_/g;
    # Remove leading slash
    $dir = substr($dir,1);

    unless (-d "$BACKUP_DIR/$dir")
    {
        system("$MKDIR -p $BACKUP_DIR/$dir");
    }

    # Get datestamp of last full backup
    my $last_full = `$LS -t $BACKUP_DIR/$dir/${dir}_full* 2>&1 | $HEAD -1`;
    chomp($last_full);
    if ($last_full =~ /No such file or directory/)
    {
        $last_full = '';
    }
    my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,
        $blksize,$blocks) = stat($last_full);

    if ($mday == 1)
    {
        # Monthly Full Backup
        system("$TAR -cf $BACKUP_DIR/$dir/${dir}_full_monthly_$datestamp.tar $backup_src > /dev/null 2>&1");
        system("$GZIP -f $BACKUP_DIR/$dir/${dir}_full_monthly_$datestamp.tar");
        system("$RM $BACKUP_DIR/$dir/${dir}_full_weekly_*");
    }
    elsif ($wday == 0 || !$last_full)
    {
        # Weekly Full Backup
        system("$TAR -cf $BACKUP_DIR/$dir/${dir}_full_weekly_$datestamp.tar $backup_src  > /dev/null 2>&1");
        system("$GZIP -f $BACKUP_DIR/$dir/${dir}_full_weekly_$datestamp.tar");
    }

    # Daily Differential Backup
    if ($mtime)
    {
        my $newer = sprintf("%02d-%s", (localtime($mtime))[3], $months[(localtime($mtime))[4]]);
        system("$TAR --newer $newer -cf $BACKUP_DIR/$dir/${dir}_diff_daily_$day.tar $backup_src > /dev/null 2>&1");
    }
    else
    {
        system("$TAR -cf $BACKUP_DIR/$dir/${dir}_diff_daily_$day.tar $backup_src > /dev/null 2>&1");
    }
    system("$GZIP -f $BACKUP_DIR/$dir/${dir}_diff_daily_$day.tar");

    print "done.n";
}

# Do Database Backups
foreach my $db (@dbs)
{
    my $db_name = $db;
    $db = "db_$db";

    unless (-d "$BACKUP_DIR/$db")
    {
        system("$MKDIR -p $BACKUP_DIR/$db");
    }

    print "Backing up $db_name database... ";

    if ($mday == 1)
    {
        # Monthly Backup
        system("$MYSQLDUMP --user=$DB_USER --password='$DB_PASS' $db_name > $BACKUP_DIR/$db/${db}_monthly_$datestamp.sql");
        system("$GZIP -f $BACKUP_DIR/$db/${db}_monthly_$datestamp.sql");
        system("$RM $BACKUP_DIR/$db/${db}_weekly_*");
    }
    elsif ($wday == 0)
    {
        # Weekly Backup
        system("$MYSQLDUMP --user=$DB_USER --password='$DB_PASS' $db_name > $BACKUP_DIR/$db/${db}_weekly_$datestamp.sql");
        system("$GZIP -f $BACKUP_DIR/$db/${db}_weekly_$datestamp.sql");
    }

    # Daily Backup
    system("$MYSQLDUMP --user=$DB_USER --password='$DB_PASS' $db_name > $BACKUP_DIR/$db/${db}_daily_$day.sql");
    system("$GZIP -f $BACKUP_DIR/$db/${db}_daily_$day.sql");

    print "done.n";
}

Call the script something like /usr/local/bin/backup, and then create a config file /usr/local/etc/backup.conf, that has the following format:
DIR /www/domain1.com
DIR /www/domain2.com
DB domain1_wp_db
DB domain2_wp_db

(Substituting locations/db names appropriate for your environment of course). If you use a different config file than /usr/local/etc/backup.conf, be sure to change that line in the script. Also, you’ll need to change the mysql root password in the script to be whatever it is for your env (or make it non-root, whichever you want, it just needs to be able to do a mysqldump on the databases)

Next, set up your crontab to run nightly:

sudo crontab -e

Add the following line:

0 1 * * * /usr/local/bin/backup > /dev/null 2>&1

That should be it! Again, make sure to do some test restores to verify that it works ok! Here’s what a typical backup directory looks like after a couple of months running the script:

[ed@halo1:/backup/www_edsalisbury.net]$ ls -l
total 144240
-rw-r--r--  1 root root  5423759 Sep 11 01:00 www_edsalisbury.net_diff_daily_Fri.tar.gz
-rw-r--r--  1 root root  1839115 Sep  7 01:00 www_edsalisbury.net_diff_daily_Mon.tar.gz
-rw-r--r--  1 root root  5787136 Sep 12 01:00 www_edsalisbury.net_diff_daily_Sat.tar.gz
-rw-r--r--  1 root root  7193167 Sep 13 01:00 www_edsalisbury.net_diff_daily_Sun.tar.gz
-rw-r--r--  1 root root  3782727 Sep 10 01:00 www_edsalisbury.net_diff_daily_Thu.tar.gz
-rw-r--r--  1 root root  2455973 Sep  8 01:00 www_edsalisbury.net_diff_daily_Tue.tar.gz
-rw-r--r--  1 root root  3268897 Sep  9 01:00 www_edsalisbury.net_diff_daily_Wed.tar.gz
-rw-r--r--  1 root root 23705401 Aug  1 01:00 www_edsalisbury.net_full_monthly_20090801.tar.gz
-rw-r--r--  1 root root 33975458 Sep  1 01:00 www_edsalisbury.net_full_monthly_20090901.tar.gz
-rw-r--r--  1 root root 31453170 Sep  6 01:00 www_edsalisbury.net_full_weekly_20090906.tar.gz
-rw-r--r--  1 root root 28556424 Sep 13 01:00 www_edsalisbury.net_full_weekly_20090913.tar.gz

Not too bad, size-wise. For all of my sites, the backup directory is about 4 GB, and will stay around that size for quite a while. The differentials get deleted and so do the weekly full backups after the monthly full completes. This makes it so that the directory only really grows when there’s a new full monthly. If you find this script useful or have issues, be sure to post a comment!