X-Recipient: archive-cygwin AT delorie DOT com DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:content-type:mime-version:subject:from :in-reply-to:date:content-transfer-encoding:message-id :references:to; q=dns; s=default; b=LHa4euz9Is1SKSF6To/AnSjBZznY nBZkQXqtzUsufzw73TiNRzEmqgm1aiMU5ic8N6CVvSjpiIGle3VOUSIzRg+OIVhH xuLVYCUqdrZtZIAMyG/Zws610tMbSJ3lzOuZM9sCJrFkSADplZKaHwV7aVt8nHEh NGuDqPjiMGmP6Fw= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:content-type:mime-version:subject:from :in-reply-to:date:content-transfer-encoding:message-id :references:to; s=default; bh=ygVQJj3hkHSSA02wyLXyLOh63iQ=; b=bx PtdeVeEY8B6lTCiTosVDD3CMibyDqo1k18jTLkAN4KJ6aPFKxod8UGLLWcsMrHEB SjOMTtiTfGLY/haKczCek9cvvMFnXquqU1WUBauZlMhvNN+OsGrSPo2hMhlDjwbN jUy+YVu/GRulTkyuhuFr0x0ChZfio5DNWfpEa58KE= Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com 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 AT redhat DOT com, H*MI:sk:9fdf98c, H*MI:sk:09f604c X-HELO: gproxy6-pub.mail.unifiedlayer.com 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 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 10:24:07 -0500 Message-Id: References: <9fdf98cf-e3d1-e453-1c98-2c206afe81c9 AT gmail DOT com> <09f604cd-61df-e0c7-b313-1dcf1ef59b4e AT gmail DOT com> <574313B3 DOT 3090703 AT redhat DOT 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 AT solidrocksystems DOT com} X-IsSubscribed: yes Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id u4NFOkGU012438 > 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. >>> >>> >>> 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. > > 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. This is ultimately Eric’s decision, but… It doesn’t _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 what. I personally don’t want to have to guess at tar’s behavior. I want to know it’s 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