Date: Mon, 9 Nov 1998 15:40:41 +1030 From: Greg Lehey <grog@lemis.com> To: Bryce Newall <data@dreamhaven.net>, Jordan Krushen <jkrushen@home.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Tape backup questions Message-ID: <19981109154041.J499@freebie.lemis.com> In-Reply-To: <Pine.NEB.3.96.981108181906.15750j-100000@ds9.dreamhaven.org>; from Bryce Newall on Sun, Nov 08, 1998 at 06:25:13PM -0800 References: <000801be0b7f$582dc7e0$0300000a@oblivion.purplemedia.com> <Pine.NEB.3.96.981108181906.15750j-100000@ds9.dreamhaven.org>
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On Sunday, 8 November 1998 at 18:25:13 -0800, Bryce Newall wrote: > On Sun, 8 Nov 1998, Jordan Krushen wrote: > >> I've just added a Seagate TapeStor 4/8Gb SCSI drive to my 2.2.7 system, and >> I'm having a hard time figuring out how to have multiple sessions added to >> the tape. When using tar with /dev/nrst0 for two consecutive files, only >> the first file written to the tape remains. > > Tar doesn't allow you to create archive files on a tape. Rather, it sees > the tape itself *as* the archive file, and allows you to add files to and > extract them from the archive file. If you want to add to an existing > tape archive, you should theoretically be able to use the -A (append) > switch on the tar command. (I've never actually tried this, so I can't > verify that it actually works.) Otherwise, tar will erase the header on > the tape and start a new one. I don't know where you get this idea. tar does allow you to create archive files on a tape. That's what it's there for. You're talking about explicitly appending to a tar archive, which used to be popular, but is a Bad Thing with streamers. # tar clf /dev/nrst0 / # tar clf /dev/nrst0 /usr # tar clf /dev/nrst0 /home This will give you three backups with the contents of each of the file systems /, /usr and /home. In Jordan's case, I'm pretty sure that both files are there. Unfortunately, streamers are a little sloppy writing file marks, and it's possible for the following to happen with the tape written above: # mt -f /dev/nrst0 rewind # tar tvf /dev/nrst0 (list of / file system) # tar tvf /dev/nrst0 (nothing) # tar tvf /dev/nrst0 (nothing) # tar tvf /dev/nrst0 (list of /usr file system) # tar tvf /dev/nrst0 (nothing) # tar tvf /dev/nrst0 (list of /home file system). Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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