Date: Sat, 27 Oct 2001 09:32:35 -0500 From: jacks@sage-american.com To: Nils Holland <nils@tisys.org>, freebsd-questions@FreeBSD.ORG Subject: Re: Funny things to do with tar... Message-ID: <3.0.5.32.20011027093235.00fa6e38@mail.sage-american.com> In-Reply-To: <20011027121324.O692-100000@jodie.ncptiddische.net>
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I wonder if it has anything to do with the fact that the CD writing process messes with the file attributes, like everything is made read-only or other attributes as well, including permissions, ownership. Here's another way: Save your tar files directly to another hard disk first (leave them there as extra safety backup if you have room). The copy those to the CD. Then copy back and watch the attributes. Then untar them on the test machine to see if it works that way.... At 12:33 PM 10.27.2001 +0200, 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 > > Best regards, Jack L. Stone, Server Admin Sage-American http://www.sage-american.com jacks@sage-american.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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