Generating files of any size

For various reasons, you may need to generate a file filled with random data. It may be for creating a test file to perform tests, such as an application efficiency test that uses a large file as input, or to test the splitting of files into many parts, or to create loopback filesystems (loopback files are files that can contain a filesystem itself and these files can be mounted similarly to a physical device using the mount command). It takes effort to create such files by writing specific programs. So we use general utilities.

How to do it...

The easiest way to create a large-size file with the given size is to use the dd command. The dd command clones the given input and writes an exact copy to the output. Input can be stdin, a device file, a regular file, or so on. Output can be stdout, a device file, a regular file, or so on. An example of the dd command is as follows:

$ dd if=/dev/zero of=junk.data bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes...