Creating large size file for testing

kushalkoolwal · 11-04-2005, 01:46 PM

I am writing a shell script which does some disk checking space and copies file here and there. Is there any way by which I can create file of size around 100MB-500MB using some command. I just need a file contents does not matter. Can I do that with the dd command? If yes, then what is the command that I need to give.?

Thanks

keefaz · 11-04-2005, 01:54 PM

100 MB :

Code:

dd if=/dev/zero of=file.out bs=1MB count=100

500 MB :

Code:

dd if=/dev/zero of=file.out bs=1MB count=500

kushalkoolwal · 11-04-2005, 02:21 PM

ahh. Thanks. Great. Also does the bs always has to be 1MB? What if I give bs=2MB and count=250 to create a 500MB space. This quesiton might be stupid but I am curious to know. Aslo I read the man page but I was not able to figure out anything from there.

Also I when I gave the following command:
dd if=/dev/zero of=file.out bs=1MB count=450
to create a file of size 450MB, it did created the file but the system got really slow after that. My windows were dragging when I try to move them around or switch from one window to another.?

Any ideas why this is happening?

Thank you once again.

keefaz · 11-04-2005, 03:12 PM

The bs is the block size read into memory before be written, so increase it
uses more memory, but not that much if you use 2MB

Now as to why it slowed down your system, I can't tell... Maybe it was caused by
some other processes

vinayak_sarate · 09-30-2008, 07:40 AM

Simple code will create a large sized file :

while [ 1 ]; do dd if=/dev/zero of=largefile bs=65535 count=1024;echo "HI"; sleep 2; done

cniki · 03-31-2010, 08:56 AM

Quote:

Originally Posted by vinayak_sarate

Simple code will create a large sized file :

while [ 1 ]; do dd if=/dev/zero of=largefile bs=65535 count=1024;echo "HI"; sleep 2; done

Maybe someone will believe you !