Archives

Archives are created using the archive command:

Model.new(:my_backup, 'My Backup') do
  archive :my_archive do |archive|
    # Run the `tar` command using `sudo`
    archive.use_sudo
    # add a file
    archive.add '/path/to/a/file.rb'
    # add a folder (including sub-folders)
    archive.add '/path/to/a/folder/'
    # exclude a file
    archive.exclude '/path/to/a/excluded_file.rb'
    # exclude a folder (including sub-folders)
    archive.exclude '/path/to/a/excluded_folder'
  end
end

• You may add as many add and exclude paths as needed.
• :my_archive will be the name of your archive.
  It will be stored within your final backup package as archives/my_archive.tar.
• You may add as many archive blocks within your model as you like.
  Just be sure that each is defined with a unique name.

Specifying a Root Path

You have two choices for how the paths within your tar archive will be stored.

• Using the root of the filesystem.
• Using a specified root path.

Filesystem Root

By default, all paths given to the add or exclude commands are expanded to their full paths from the root of the filesystem. Relative paths are expanded based on the current working directory where backup perform is executed. When files are added to the tar archive, the leading / is preserved.

For example, given the following:

archive :my_archive do |archive|
  archive.add 'my_data/save.me'
  archive.add '/opt/save.me.too'
end

If backup perform is run in /home/my_user, your tar file contents would be:

$ tar -tvf my_archive.tar
/home/my_user/my_data/save.me
/opt/save.me.too

When extracting this archive, the leading / will be automatically stripped by default. So, if you extracted this in /home/my_user/tmp, it would create the following:

$ tar -xvf my_archive.tar
/home/my_user/tmp/home/my_user/my_data/save.me
/home/my_user/tmp/opt/save.me.too

However, you may instruct tar not to strip the leading / using the -P option, and it will extract the files back to their original location:

$ tar -xvPf my_archive.tar
/home/my_user/my_data/save.me
/opt/save.me.too

Specified Root

To set the root path for your archive, you can use the root command. When a root path is given, all relative paths added using add or exclude are taken as relative to the root path given.

archive :my_archive do |archive|
  archive.root '/home/my_user'
  archive.add 'my_data/save.me'
  archive.add '/opt/save.me.too'
end

This will instruct tar to change it’s working directory to /home/my_user when creating the archive. In this example, this means that tar will create the following archive:

$ tar -tvf my_archive.tar
my_data/save.me
/opt/save.me.too

Note that it’s still possible to add files/folders from outside the root path using an absolute path. Any leading / will be preserved, so the information above still applies. Be careful when extracting archives with mixed relative/absolute paths without instructing tar to preserve the leading /. For example, the path etc/my_file and /etc/my_file would both extract to ~/tmp/etc/my_file by default if extracted in ~/tmp.

Also note that the root path given will be expanded. This means that if given as archive.root '.', the root path will be the current working directory where backup perform was executed. archive.root '~/' will expand to your $HOME directory. Of course, absolute paths given will be used as-is.

Compressing Archives

To create a compressed archive, simply add a Compressor to your Backup model.

Model.new(:my_backup, 'My Backup') do
  archive :my_archive do |archive|
    # add/exclude files/folders
  end

  compress_with Gzip

  # Storages, etc...
end

The output of the tar command will be piped through the selected compressor. So, if Gzip is the compressor, the archive would be saved in your final backup package as archives/my_archive.tar.gz.

Additional Tar Options

Archives also have a tar_options method, which can be used to add additional options to the tar command used to create the archive.

For example, to have tar follow symlinks and store extended attributes, you could use:

archive :my_archive do |archive|
  archive.add '/path/to/a/file.rb'
  archive.tar_options '-h --xattrs'
end

Note: Do not add compression flags using tar_options. To compress your archives, add a Compressor.

Archiving Files That May Change

Creating an Archive that includes files that may change during the backup process may cause your backup to complete with Warnings. If you have any Notifiers configured to send messages on_success or on_warning, you will be notified that the job completed with Warnings.

Backup supports both GNU and BSD tar, and each will behave differently when the following actions occur.

File is Removed

If a file is removed while it is being archived, GNU tar will detect this and issue a warning. However, you may elect to ignore this warning by adding --warning=no-file-removed to your tar_options.

archive :logs do |archive|
  archive.add '/var/apps/my_app/logs/'
  archive.tar_options '--warning=no-file-removed'
end

BSD tar will issue a warning if this occurs. There is no way to suppress this.

In all cases, the archive will continue to be created and the backup job will continue. If warnings are issued, this will cause your backup to complete with Warnings.

File is Changed

If a file is changed while it is being archived, GNU tar will detect this and issue a warning. However, you may elect to ignore these warnings by adding --warning=no-file-changed to your tar_options.

archive :logs do |archive|
  archive.add '/var/apps/my_app/logs/'
  archive.tar_options '--warning=no-file-changed'
end

BSD tar will not issue a warning if this occurs.

In all cases, the archive will continue to be created and the backup job will continue. If warnings are issued, this will cause your backup to complete with Warnings.

Note: If you wish to have GNU tar ignore warnings when files are changed or removed, both options must be used.

archive :logs do |archive|
  archive.add '/var/apps/my_app/logs/'
  archive.tar_options '--warning=no-file-changed --warning=no-file-removed'
end

File or Folder Does Not Exist

If a file or folder you have explicitly added using archive.add does not exist when the archive is performed, then both GNU and BSD tar will output warnings. These warnings may not be suppressed. The archive will continue to be created, and your backup will be completed with Warnings.

If possible, only add parent folders you know will exist. This way if files/folders are removed below the parent before the archive is performed, no warnings will occur. If they are removed while the archive is being performed, this will fall under the previous sections where suppressing warnings may be possible.

File or Folder is Not Readable

If any files or folders are encountered that can not be read, both GNU and BSD tar will output warnings. These warnings may not be suppressed. The archive will continue to be created, and your backup will be completed with Warnings.