Re: du -sh Error

[Michael Stone]

On Sat, Jun 15, 2002 at 07:43:35PM +0200, Daniel Holbach wrote:
> address@hidden:/var/spool/oops/storages# du -sh
> 24k     .
> address@hidden:/var/spool/oops/storages# ls -l
> -rw-r--r--    1 proxy     proxy   20971520 Jun 15 19:35 oops_storage

Probably a sparse file. For example:

(42)osgiliath:/tmp> dd if=/dev/zero bs=1048576 count=0 seek=20
of=sparsefile
0+0 records in
0+0 records out
(43)osgiliath:/tmp> ls -l sparsefile 
-rw-rw-r--    1 mstone   mstone   20971520 Jun 15 15:17 sparsefile
(44)osgiliath:/tmp> du -sk sparsefile 
0       sparsefile
(45)osgiliath:/tmp> ls -ls sparsefile
   0 -rw-rw-r--    1 mstone   mstone   20971520 Jun 15 15:17 sparsefile

In unix it is possible to create a file with a given filesize but with
no data associated with it. In this case, no actual disk space is used
by the file. This is a mechanism commonly used by, e.g., databases and
core dumps--data can be stored at a particular location within a file,
not necessarily at the beginning, without wasting disk space. du
measures the disk blocks used by a file, while ls -l shows the logical
file size. You can also use ls -s to show the number of blocks allocated
to a file, or ls -ls to compare the number of blocks with the file size
(the number of blocks will be the first digit in the output.)

-- 
Mike Stone