Automating Remote Backups

ssmtp is a replacement for Sendmail that is considerably less complex to configure and use. It is not intended to retrieve mail, however. It is intended only for outbound e-mail. It has a small and simple configuration file, and when used as a replacement for Sendmail, it will be used by command-line programs like mail for sending e-mail.

ssmtp is not typically provided by Linux distributions, but the source can be found with a Google search on the Internet. Follow the package directions to build and install under /usr/local. Then, replace sendmail with ssmtp by setting a symbolic link from /usr/sbin/sendmail to the installation location of ssmtp.

$ mv /usr/sbin/sendmail /usr/sbin/sendmail.orig
$ ln -s /usr/local/sbin/ssmtp /usr/sbin/sendmail

If your distribution supports the alternatives tool, you may prefer to use it instead of the symbolic link to let the system use ssmtp instead of Sendmail. Note that, as a bonus, when the author replaced Sendmail with ssmtp, LogWatch suddenly began sending nightly reports via e-mail, allowing me a view on system activity I never had seen before and which many Linux users probably never have seen before either.

Backing up system configuration files is handled by a Perl script that verbosely lists the files to be copied to a location on the /home partition. The script is run by root via cron every night to copy the configuration files to a directory in user data space (under /home):

#!/usr/bin/perl
$filelist = <<EOF;
/etc/passwd
/etc/group
...  # other config files to backup
EOF

@configfiles = split('\n', $filelist);
for (@configfiles)
{
    if (-e $_) { $files = join(" ", $files, $_); }
    elsif (index($_, "*") >= 0) {
        $files = join(" ", $files, $_);
    }
}
print "Creating archive...\n";
`tar Pczf $ARGV[0]/systemfiles.tar.gz $files`;

This brute-force method contains a list of the files to back up, joins them into a single tar command and builds a tar archive of those files on the local system. The script is maintained easily by modifying the list of files and directories. Because the configuration files are copied locally to user data space, and user data space is backed up separately, there is no need for rsync commands here. Instead, the system configuration tar archive is kept with user data and easily referenced when doing restores or system upgrades. The backup script functions as a full backup, replacing the tar archive with each execution unless a different destination is specified as a command-line argument.

What this script lacks in Perl excellence it makes up for in simplicity of maintenance. Note that the “retail” version of this script ought to include additional error checking for the command-line argument required to specify the location to save the archive file.

Like system configuration files, databases are backed up to user data directories to be included in the user data backups. Databases are of slightly higher importance in day-to-day use, so this script uses a seven-day rotating cycle for database file dumps. This allows restoring backups from up to a week ago without overuse of disk space for the backups. This method is not incremental, however. It is a set of seven full backups of each database.

Like the system configuration file backup script, this script lists the items to back up. The mysqldump command assumes no password for the root user to access the databases. This is highly insecure, but for users behind a firewall, it is likely the easiest way to handle database management:

#!/usr/bin/perl -w
use File::Path qw(make_path remove_tree);
my $BUDIR1="/home/httpd/db";
my ($sec,$min,$hour,$mday,$mon,$year,
    $wday,$yday,$isdst) = localtime time;
$year += 1900;
$mon += 1;
if ($mon < 10 )  { $mon  = "0".$mon; }
if ($mday < 10 ) { $mday = "0".$mday; }
$TODAY = $wday;

@dbname = (
    "mysql",
    "wordpress",
);

make_path ("$BUDIR1/$year");
foreach $db (@dbname) {
    $cmd = "mysqldump -B -u root $db " .
           "-r $BUDIR1/$year/$TODAY-$db.sql";
    system("$cmd");
}

print ("Database Backups for " .
       $year . "/" . $mon . "/" .
       $mday . "\n");
print ("-------------------------------\n");
open(PD, "ls -l $BUDIR1/$year/$TODAY-*.sql |" );
@lines = <PD>;
close(PD);
$output = join("\n", @lines);
print ($output);

Unlike the configuration file backup script, this script prints out the list of files that have been created. This provides a quick, visual feedback in the e-mailed report that the backups produced something meaningful.