From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 122610 invoked by alias); 23 May 2016 14:57:42 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 122595 invoked by uid 89); 23 May 2016 14:57:40 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.3 required=5.0 tests=AWL,BAYES_00,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 spammy=eblakeredhatcom, stamps, U*eblake, eblake@redhat.com X-HELO: mail-wm0-f42.google.com Received: from mail-wm0-f42.google.com (HELO mail-wm0-f42.google.com) (74.125.82.42) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Mon, 23 May 2016 14:57:30 +0000 Received: by mail-wm0-f42.google.com with SMTP id z87so51912937wmh.0 for ; Mon, 23 May 2016 07:57:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to; bh=lnYUHtZP19ntIHiWo8qRTyGFQfKo5OGbjgcHwar5ghg=; b=AUVPyxIoMoqheTd6gej2l28nnVEEVssf6v2Fb49zWtHOM71op5sX0Q1+de/Fm3l/TW xf1/pl8OR5JKLuchuV2SrFsY4Q1xBFkK94KfFi3MU6lm3U12yxjAm/xt11xT7RWkzIvR 7kiOoWHaIlvResB80l4m9CSYWEpSXJOJNlywZ5FuXma7HIX8mXVsuLRw3NCvI9SA7jYK gw2I934EMmN8untq5VpJSVYNDHfFqjedK6HnkkmJLjgBPAxZarUgRtZOqa9mKo5wA4hh G3jzPKJ4llp2e5snxqvk/5crlsFbB2whVMHP7XSnhtpCuK9Wrks6y+92BcemVd5krhez 26UA== X-Gm-Message-State: AOPr4FXISqxl4wenyetV6aO0bthKN7uzF5ElZ/mDWZY8DjlFYtaTCruGjhNfLpziw8wQdjGWtD/Da2FYkkTaiA== MIME-Version: 1.0 X-Received: by 10.28.45.9 with SMTP id t9mr18642869wmt.89.1464015447206; Mon, 23 May 2016 07:57:27 -0700 (PDT) Received: by 10.194.56.134 with HTTP; Mon, 23 May 2016 07:57:27 -0700 (PDT) In-Reply-To: <574313B3.3090703@redhat.com> References: <9fdf98cf-e3d1-e453-1c98-2c206afe81c9@gmail.com> <09f604cd-61df-e0c7-b313-1dcf1ef59b4e@gmail.com> <574313B3.3090703@redhat.com> Date: Mon, 23 May 2016 14:57:00 -0000 Message-ID: Subject: =?UTF-8?Q?Re=3A_tar_incremental_backups_and_ctime=E2=80=8F_problem?= From: x y To: cygwin@cygwin.com Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2016-05/txt/msg00267.txt.bz2 >mtime is fakeable, ctime is not. Using only mtime makes it likely that >your incremental backup will miss files. I don't have any good reason >to differ from upstream behavior here. Hi Eric, The problem is not faking time stamps. Even commercial Windows backup programs are checking the modification time to identify the modified files. Consider that you have a lot of files opened and closed without any modification in your company. Because of the priority of the ctime time stamp, reintroducing all of those files to the incremental backup does not make any sense. tar has also the capacity to create differential backups with the condition of taking care of the snapshot file. The ctime issue can result in unnecessarily big differential backups filled with unmodified files. Cygwin tar can be a good alternative for Windows users to do differential \ incremental backups but the ctime problem must be solved. On Mon, May 23, 2016 at 5:29 PM, Eric Blake wrote: > On 05/23/2016 03:18 AM, x y wrote: >> It is not clear to me your expectation: >> - are you asking how to use ctime to select the file with tar alone ? >> It is not possible for my understanding of the manual. >> >> - Are you asking the package maintainer to change the behaviour of >> cygwin tar ? Unlikely to happen, but I leave to him. >> >> Regards >> Marco >> >> >> Hi Marco, >> >> Sorry, I am new to the mailing list. If I am not wrong, tar is >> checking both of the ctime and mtime values to compare files during >> incremental backups. Since opening and closing a MS document without >> changing the content updates ctime, it would be preferable to add a >> new option to tar to use only mtime for file comparing during >> incremental backups. > > mtime is fakeable, ctime is not. Using only mtime makes it likely that > your incremental backup will miss files. I don't have any good reason > to differ from upstream behavior here. > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple