Date: Mon, 25 Feb 2008 13:36:17 +0100 From: "Martin Laabs" <martin.laabs@mailbox.tu-dresden.de> To: freebsd-hackers@freebsd.org Subject: emulate an end-of-media Message-ID: <op.t62ymri0724k7f@martin>
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Hi, I'll write a script that back up my data on dvd-r and dvd-rams. (And some incremental backups also at some internet storage services.) Therefore I'd like to use dump. It is not too hard to create dump-volumes with fixed size through the -B option. But now I'd like to use some sort of compression. (bzip2 seems far to be to slow. Maybe I'll use gzip or compress) However - with compression I can't use the -B switch of dump because I can't be sure about the compression ratio. This means I have to use the '-a' switch. With that switch enabled, dump starts a new volume after it detects an EOM signal. Because dump itself does not support compression I have to build a pipe like that: dump -aL0 -f - /MYFILESYSTEM|compress -c|aespipe ...|cdrecord dev=3D... = - This obvisouly does not work. I tried to wrote a script that close the pipe after the amount of compressed data reached 4.6GB. But if I close the pipe in that script dump aborts (because of the broken pipe) at all instead of just starting a new volume. What I'd need is a magaic pipe device that converts a ordenary close at the one side to an EOM at the other. Then I could do something like this: dump -aL0 -f /dev/MyMagicDevice & dd if=3D/dev/MyMagicDevice bs=3D1M count=3D4600|./compress -c|cdrecord d= ev=3D... - Before I try to write a kernel module that will do the job (I never wrote a freebsd kernel module before but I think it is some fun to learn that.) I want to ask if anyone see another solution for that problem. (Maybe patching dump - but I don't want to fudge in the CORE source.) Thank you in advance, Martin L. PS: Splitting up the huge (maybe compressed) dump file (also in stream operation) is not a good idea beacause I'd need to insert all the media - even if I resore only a single file.
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