sparse image

[Vincent Hoffman]

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 at 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 at ostracod /scratch/media]# ls -lh foo.img
-rw-r--r--  1 root  wheel   1.0G Jun 23 11:45 foo.img
[root at ostracod /scratch/media]# du -h foo.img
 48K    foo.img
[root at ostracod /scratch/media]# mdconfig -a -t vnode -f foo.img
md0
[root at ostracod /scratch/media]# gpart create -s gpt md0
md0 created
[root at ostracod /scratch/media]# gpart add -t freebsd-ufs md0
md0p1 added
[root at 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 at ostracod /scratch/media]# !ls
ls -lh foo.img
-rw-r--r--  1 root  wheel   1.0G Jun 23 11:46 foo.img
[root at ostracod /scratch/media]# !du
du -h foo.img
736K    foo.img
[root at ostracod /scratch/media]# mount /dev/md0p1 /mnt/foo/
[root at ostracod /scratch/media]# df -h | grep foo
/dev/md0p1                  989M    4.0K    910M     0%    /mnt/foo
[root at ostracod /scratch/media]#

Hope this is helpful.
Vince
 
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