command to create a large file

[John Meissner]

I'm trying to test someting and need to create a large file - about 5Gb. I can't think of the command to do this. Thanks for the help.

[Patrick Wallek · Accepted solution]

prealloc is what you want.

# prealloc test 5000000000

The above shoud be 5,000,000,000 bytes or approximately 5GB. It will take a while for prealloc to create the file, but it will get done eventually.

[A. Clay Stephenson]

dd if=/dev/zero bs=256k count=20000 of=mybigfile

If this is 10.20, you will need to create /dev/zero
mknod /dev/zero c 3 0x03
chmod 444 /dev/zero

If early 11.0,
mknod /dev/zero c 3 0x04

but you will probably already have /dev/zero on 11.x.

[John Meissner]

thanks for the incredibly fast answers guys!!!

This forum is SUCH an incredibly useful tool... from critical issues to something stupid like this. Thanks for the answers and for the help