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Editor: PaulWise
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Current implementation should sort them in alphabetical (qsort / [[http://linux.die.net/man/3/strcmp|strcmp]]) order, for each of the top directories and then descend, doing same sort for each child directory. Current implementation should sort them in alphabetical (qsort / [[DebianMan:3/strcmp|strcmp]]) order, for each of the top directories and then descend, doing same sort for each child directory.

This site describes ?Mempo's extensions to the GNU tar file archive program.

This page has a maintainer: :-) UserRfree (+ Teams/MempoTeam)

This software is (2014-01) experimental addition to Debian, though we hope to in time move it officially to Upstream and to Debian, see ?Mempo#integration for general download&install instructions for Mempo software.

Newest code download should be here: https://github.com/mempo/various/commits/master/tar or try other ?Mempo#downloads.

New option

--sort-input

This new option was added to tar: store all added files in sorted way, so that they are always added in same order, when creating (or appending) archive. Current implementation should sort them in alphabetical (qsort / strcmp) order, for each of the top directories and then descend, doing same sort for each child directory.

Identical tar

With above extensions it should now be trivial to produce .tar files that always are binary identical (and thus have same checksum) if input files have identical content, no matter what UID/GID, user-names, file times or order of files on disk exists each time.

Thus the command: 

tar --sort-input --owner=root --group=root --numeric-owner cf foo.tar input/

should produce identical foo.tar file out of data in input/ directory, verify it with command tar tvf foo.tar.

Perhaps on strange systems where there would be user "root" with UID other then 0, it could not work properly, how ever no such system probably exists and likely it's violating standards so can't be counted as a real use case.

Install

Get and build modified tar:

  • Install dependencies: aptitude install byacc bison

  • Get sources: git clone git@github.com:mempo/various.git

  • cd various/tar and ./bootstrap

  • Because bootstrap overvrite gnu/savedir.c (--sort-input option) we need to get good version from git: git checkout gnu/savedir.c

  • ./configure ; make

  • This step is important in building SameKernel. Copy binary to local folder: cp src/tar ~/.local/usr/bin/tar

Alternatives

Instead of using --faketime one might want to use this script: http://paste.debian.net/76195 rewrite_faketime_tar_dates_script.txt