From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 53032 invoked by alias); 23 May 2016 15:24:30 -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 51819 invoked by uid 89); 23 May 2016 15:24:27 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.5 required=5.0 tests=BAYES_05,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=eblakeredhatcom, eblake@redhat.com, H*MI:sk:9fdf98c, H*MI:sk:09f604c X-HELO: gproxy6-pub.mail.unifiedlayer.com Received: from gproxy6-pub.mail.unifiedlayer.com (HELO gproxy6-pub.mail.unifiedlayer.com) (67.222.39.168) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with SMTP; Mon, 23 May 2016 15:24:20 +0000 Received: (qmail 21393 invoked by uid 0); 23 May 2016 15:24:15 -0000 Received: from unknown (HELO cmgw4) (10.0.90.85) by gproxy6.mail.unifiedlayer.com with SMTP; 23 May 2016 15:24:15 -0000 Received: from box867.bluehost.com ([69.195.124.67]) by cmgw4 with id xrQA1s00a1TMts501rQDt5; Mon, 23 May 2016 09:24:15 -0600 X-Authority-Analysis: v=2.1 cv=EftbHpWC c=1 sm=1 tr=0 a=x/h8IXy5FZdipniTS+KQtQ==:117 a=x/h8IXy5FZdipniTS+KQtQ==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=IkcTkHD0fZMA:10 a=CnPQkyIfcMwA:10 a=xmZoPxhebIwA:10 a=yrkiwgmsf1kA:10 a=Wa7ptvNIr5gA:10 a=20KFwNOVAAAA:8 a=R2KNy1cDpNDN3Zb9hfcA:9 a=QEXdDO2ut3YA:10 a=e_O65bzb51kRm2y5VmPK:22 Received: from [192.154.176.197] (port=19490 helo=[10.1.84.178]) by box867.bluehost.com with esmtpsa (TLSv1:ECDHE-RSA-AES256-SHA:256) (Exim 4.86_2) (envelope-from ) id 1b4riE-0003wv-AS for cygwin@cygwin.com; Mon, 23 May 2016 09:24:10 -0600 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: =?utf-8?Q?Re=3A_tar_incremental_backups_and_ctime=E2=80=8F_probl?= =?utf-8?Q?em?= From: Vince Rice In-Reply-To: Date: Mon, 23 May 2016 15:24:00 -0000 Content-Transfer-Encoding: quoted-printable Message-Id: References: <9fdf98cf-e3d1-e453-1c98-2c206afe81c9@gmail.com> <09f604cd-61df-e0c7-b313-1dcf1ef59b4e@gmail.com> <574313B3.3090703@redhat.com> To: Cygwin Mailing List X-Identified-User: {3986:box867.bluehost.com:solidrr2:solidrocksystems.com} {sentby:smtp auth 192.154.176.197 authed with vrice@solidrocksystems.com} X-IsSubscribed: yes X-SW-Source: 2016-05/txt/msg00268.txt.bz2 > 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. >>>=20 >>> - Are you asking the package maintainer to change the behaviour of >>> cygwin tar ? Unlikely to happen, but I leave to him. >>>=20 >>>=20 >>> Hi Marco, >>>=20 >>> 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. >>=20 >> 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. >=20 > Hi Eric, >=20 > The problem is not faking time stamps. Even commercial Windows backup > programs are checking the modification time to identify the modified > files. >=20 > 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. >=20 > Cygwin tar can be a good alternative for Windows users to do > differential \ incremental backups but the ctime problem must be > solved. This is ultimately Eric=E2=80=99s decision, but=E2=80=A6 It doesn=E2=80=99t _have_ to be solved. If someone wants to use Cygwin tar = as a backup, then that someone lives with the fact that tar uses ctime. The= differential might be a little too big, but no actual harm is done. So wha= t. I personally don=E2=80=99t want to have to guess at tar=E2=80=99s behavior.= I want to know it=E2=80=99s the same on Cygwin as elsewhere. -- 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