Date: Sat, 16 Jun 2012 14:59:20 +0200 From: Pieter de Goeje <pieter@degoeje.nl> To: freebsd-hackers@freebsd.org Cc: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, d@delphij.net Subject: Re: BIO_DELETE equivalent for file on FFS filesystem Message-ID: <201206161459.20596.pieter@degoeje.nl> In-Reply-To: <alpine.BSF.2.00.1206140647080.72545@wojtek.tensor.gdynia.pl> References: <alpine.BSF.2.00.1205261704590.70782@wojtek.tensor.gdynia.pl> <4FD94240.6060806@delphij.net> <alpine.BSF.2.00.1206140647080.72545@wojtek.tensor.gdynia.pl>
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On Thursday 14 June 2012 06:48:14 Wojciech Puchar wrote: > >> file to take 900MB or... can i call some system function to "punch" > >> holes? > > > > I think you can only truncate the file at this time, pretty much like > > brk() works for memory. > > BAD. suppose i keep windoze VM image on filesystem which takes 10GB but > uses 5GB. > > i could write simple program to find out what blocks are unused and > then...do nothing. Actually you can. Use dd if=infile of=outfile conv=sparse to convert a file to a sparse file. This obviously only works on filesystems supporting sparse files, such as UFS. Regards, Pieter
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