Date: Sat, 27 Oct 2001 18:02:44 -0400 (EDT) From: Stephen Hovey <shovey@buffnet.net> To: Nils Holland <nils@tisys.org> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Funny things to do with tar... Message-ID: <Pine.BSF.4.05.10110271802190.10637-100000@buffnet11.buffnet.net> In-Reply-To: <20011027121324.O692-100000@jodie.ncptiddische.net>
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The only backup method native to the install that I DONT have trouble restoring afterwards with = is pax On Sat, 27 Oct 2001, Nils Holland wrote: > Hi folks, > > well, in the following I will talk about some strange experiences I have > recently made usig "tar". Probably some of you will have some suggestions > as to how to make my future tar-esperiences less strange. In that case, > I'd be glad to hear about it! > > Ok, the situation was like that: I started investigating in the > possibility of using tar together with CD-RW media in order to back up my > system. I thought the best thing I might do was trying it out under real > world conditions, which means creating a backup of machine 1 and then > extract it back to machine 2, which I have put together especially for > this test. > > So let's do it, I thought, and had a look at the tar man page. I decided > that I could simply use tar with the standards -c option, then tell it > that I wanted multiple volumes (-M) and that the volumes should be > CD-sizes (-L). > > I started tar like that, created multiple .tar files on my hard disk, and > burned them on CD. Note that I made an ISO-fs of each .tar file first, as > pervious experiences have shown that burning a "raw" .tar file to CD > causes problems that manifest themselves that during the extraction > process tar will not be able to detect the end-of-file, so it will abort > with a lot of read errors once it has reached the end of the first CD. > Making an ISOFS from each .tar file solves that issue. > > Let's go ahead: Finally, all my CDs were ready, containing the complete > /usr partition of my work machine. I then headed over to my test machine > to restore the CDs. It did in fact work, without any obvious error > messages! > > The problematic part begins here: Upon having extracted the tar-CDs, I > tried to see if the extracted data was actually usable. In order to find > that out, I decided to start a few programs and see if them run. > Interestingly, when I started X with KDE, KDE didn't want to start. > kdeinit (as well as several other KDE processes) crashed and dumped core. > I tried to investigate on that issue, but without luck. > > Eventually, I erased the whole /usr partition on my test machine, and used > NFS to directly copy /usr over from my work machine to my test machine. > After that operation had completed, KDE would run again! > > So, what have I learned? Obviously, the data extracted from my .tar-CDs > was at least partly corrupted, as copying the same data via NFS worked. > All of this makes the issue extremely complicated: I don't know if the > data got corrupted during creation of the .tar files, during the burncd > process, or during the extraction process. Furthermore, I don't know if I > should probably look for the fault in the CD-RW writer, in the CD-ROM > drive that read the data, or if I should suspect I have bad CD-RW media. > All I know is that a backup process like this is not a good thing to use > for actually backing up important files. > > So, any suggestions? Is anybody using tar + CD-RW and can tell me about > successes or similar failures? Any ideas how I can better make sure that > the data on my CD-RW media is actually in good working condition? I'd be > glad to hear about anything related to this issue! > > Greetings > Nils > > Nils Holland > Ti Systems - FreeBSD in Tiddische, Germany > http://www.tisys.org * nils@tisys.org > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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