Linux Shell Scripting Cookbook - Third Edition

How to do it...

The easiest way to create a large file of a given size is with 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, and so on. Output can be stdout, a device file, a regular file, and 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 (1.0 MB) copied, 0.00767266 s, 137 MB/s

This command creates a file called junk.data containing exactly 1 MB of zeros.

Let's go through the parameters:

• if defines the input file
• of defines the output file
• bs defines bytes in a block
• count defines the number of blocks to be copied

Be careful while using the dd ...