howtos

Random 1GB file

To create a random file (random name, random data) that is 1GB in size, you can use:

dd \
  if=/dev/urandom \
  of=/some_folder/`tr -dc A-Za-z0-9 </dev/urandom | head -c 26` \
  iflag=fullblock \
  oflag=direct \
  bs=64M \
  count=16 \
  status=progress

Note that you need to replace some_folder in the above command to the actual folder where you want the random files to be generated.

The sub command tr -dc A-Za-z0-9 </dev/urandom | head -c 26 simply generates a random string containing 26 characters.

If you want to loop the command, and create N random files, you can use the following:

for i in {1..N}; do COMMAND; done

Where COMMAND should be replaced with the command to create 1 random file.

Sample bash script

Here is a Bash script that will create 869 random files, each being 1GB in size. Make sure to properly set FOLDER_TO_FILL.

#!/bin/bash

FOLDER_TO_FILL=/some/system/path

for i in {1..869}; do
echo "Writing random file ${i} of 869:"
  dd \
    if=/dev/urandom \
    of=$FOLDER_TO_FILL/`tr -dc A-Za-z0-9 </dev/urandom | head -c 26` \
    iflag=fullblock \
    oflag=direct \
    bs=64M \
    count=16 \
    status=progress
done

echo "done; without errors ;)"
exit 0

Using dcfldd tool

There is a tool available to write random data to a device called dcfldd. You can install it on any Linux system. For example, on a Debian based system:

sudo apt-get install dcfldd

Then figure out the device name from dmesg or gparted. Once you know the device name (for example /dev/sda), you can completely overwrite it with random data:

sudo dcfldd \
  if=/dev/urandom \
  of=/dev/sda \
  statusinterval=10 \
  status=progress \
  bs=10M \
  conv=notrunc

After the device is completely wiped, use gparted to format it with a new file system.

about these howtos

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