Date: Wed, 30 Jun 2010 13:19:43 +0800 From: Aiza <aiza21@comclark.com> To: Vincent Hoffman <vince@unsane.co.uk> Cc: freebsd-questions@freebsd.org Subject: Re: sparse image Message-ID: <4C2AD3EF.5020803@comclark.com> In-Reply-To: <4C21E7F8.2050802@unsane.co.uk> References: <4C21E163.70003@comclark.com> <4C21E7F8.2050802@unsane.co.uk>
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Vincent Hoffman wrote: > On 23/06/2010 11:26, Aiza wrote: >> Is there an equivalent of the MAC sparseimage on FreeBSD? > If you mean you would like to make a sparse file and attach it using > mdconfg then > dd if=/dev/zero of=/path/to/outfile bs=1M seek=1024 count=0 > This will give you a sparse file that reports a gig in size, but only > uses whats actually in use. > you can then use mdconfig(8) to allow this to be partitioned formatted > and mounted. > Example below. see also > http://www.freebsd.org/doc/en/books/handbook/disks-virtual.html although > that example doesnt use a spare file. > > [root@ostracod /scratch/media]# dd if=/dev/zero of=foo.img bs=1M > seek=1024 count=0 > 0+0 records in > 0+0 records out > 0 bytes transferred in 0.000066 secs (0 bytes/sec) > [root@ostracod /scratch/media]# ls -lh foo.img > -rw-r--r-- 1 root wheel 1.0G Jun 23 11:45 foo.img > [root@ostracod /scratch/media]# du -h foo.img > 48K foo.img > [root@ostracod /scratch/media]# mdconfig -a -t vnode -f foo.img > md0 > [root@ostracod /scratch/media]# gpart create -s gpt md0 > md0 created > [root@ostracod /scratch/media]# gpart add -t freebsd-ufs md0 > md0p1 added > [root@ostracod /scratch/media]# newfs /dev/md0p1 > /dev/md0p1: 1024.0MB (2097084 sectors) block size 16384, fragment size 2048 > using 6 cylinder groups of 183.72MB, 11758 blks, 23552 inodes. > super-block backups (for fsck -b #) at: > 160, 376416, 752672, 1128928, 1505184, 1881440 > [root@ostracod /scratch/media]# !ls > ls -lh foo.img > -rw-r--r-- 1 root wheel 1.0G Jun 23 11:46 foo.img > [root@ostracod /scratch/media]# !du > du -h foo.img > 736K foo.img > [root@ostracod /scratch/media]# mount /dev/md0p1 /mnt/foo/ > [root@ostracod /scratch/media]# df -h | grep foo > /dev/md0p1 989M 4.0K 910M 0% /mnt/foo > [root@ostracod /scratch/media]# > > Hope this is helpful. > Vince > Thanks Vince this was very helpful. I was able to create a sparse image jail, but when I used cpio to duplicate the sparse file to other jails I lost the sparseness of the file. Is there a way to copy a sparse file and keep it intact?
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