Automating Backups

Problem

You want to make a dated archive of a directory to burn to CD or otherwise store on backup media.

Solution

This script copies a directory to a timestamped backup. It reuses the File.versioned_ filename method defined in Recipe 6.14, so you can create multiple backups in the same time period:

	require fileutils

	def backup(from_dir, to_dir, time_format="-%Y%m%d")
	 from_path, from_name = File.split(from_dir)
	 now = Time.now.strftime(time_format)
	 Dir.mkdir(to_dir) unless File.exists? to_dir
	 unless File.directory? to_dir
	 raise ArgumentError, "Not a directory: #{to_dir}"
	 end
	 to = File.versioned_filename(File.join(to_dir, from_name + now))
	 FileUtils.cp_r(from_dir, to, :preserve=>true)
	 return to
	end

	# This method copied from "Backing Up to Versioned Filenames"
	class File
	 def File.versioned_filename(base, first_suffix=".0")
	 suffix = nil
	 filename = base
	 while File.exists?(filename)
	 suffix = (suffix ? suffix.succ : first_suffix)
	 filename = base + suffix
	 end
	 return filename
	 end
	end

	# Create a dummy directory
	Dir.mkdir(
ecipes)
	# And back it up.
	backup(
ecipes, /tmp/backup) # => "/tmp/backup/recipes-20061031"
	backup(
ecipes, /tmp/backup) # => "/tmp/backup/recipes-20061031.0"
	backup(
ecipes, /tmp/backup, -%Y%m%d-%H.%M.%S)
	# => "/tmp/backup/recipes-20061031-20.48.56"

Discussion

The backup method recursively copies the contents of a directory into another directory, possibly on another filesystem. It uses the time-based scheme you specify along with versioned_filename to uniquely name the destination directory.

As written, the backup method uses a lot of space: every time you call it, it creates an entirely new copy of every file in the source directory. Fortunately, the technique has many variations. Instead of copying the files, you can make a timestamped tarball with the techniques from Recipe 12.10. You can archive the files to another computer with the techniques from Recipe 14.11 (although to save space, you should use the rsync program instead). You could even automatically check your work into a version control system every so often; this works better with text than with binary files.

See Also

• Recipe 6.14, "Backing Up to Versioned Filenames"
• Recipe 12.10, "Compressing and Archiving Files with Gzip and Tar"
• Recipe 14.11, "Copying a File to Another Machine"