Cross-Platform Backup Software

[Lennart Sorensen]

On Wed, Oct 03, 2007 at 03:01:28PM -0400, Christopher Browne wrote:
> I'd actually tend to prefer cpio to tar, for this application.
> 
> tar expects you to specify sets of directories/directories, and if
> you're doing anything particularly fancy in terms of modifying the set
> of files, in order to exclude certain undesired files, the sets of
> parameters get progressively more and more complex.
> 
> In contrast, with cpio, the inputs tend to be simpler:  if you have
> something that generates lists of desired files, then you can simply
> submit that to cpio, telling it what to grab.  Thus:
> 
> $ program_generating_list_of_files_to_be_backed_up |
> filter_to_modify_this | cpio -o | bzip2 >
> /var/backup/my-latest-backup.cpio.bz2

afio is actually nice in that it can gzip the files individually, while
keeping the header for each file in the archive uncompressed, which
allows much faster seeks and restores of individual files in an archive.
Anything that uses gzip or bzip2 after creating the archive requires
decompressing the whole thing to get at any file in the archive.  it is
really just a much better cpio.

> Doing sophisticated things, on the front end, does NOT forcibly make
> it more complex to extract data from the archive.
> 
> This argues strongly for using standard or quasi-standard formats.
> There are four that seem worth considering:
> 
> a) POSIX tar (!= GNU tar; GNU tar has a number of extensions)
> b) GNU tar
> c) cpio (which, I should note, is the format used internally by RPM)
> d) afio (a more advanced version of CPIO, generally command line
> compatible; likes to compress files; cpio can be used to recover afio
> archives, in a pinch...)
> 
> To a degree, they seem in order of increasing preferability to me.

There is also star for really advanced tar features like your file list
control and such that you said made cpio better than tar.  Of course it
is written by that cdrecord guy, so that maybe a point against it. :)

--
Len Sorensen
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