Creating Dummy Files
I have created dummy files two times or so now. Now, what do I mean when I say a dummy file? In my case, I mean a file which doesn’t have any actual content, instead it has more like some random dummy data. Similar to the lorem ipsum content that people use for placeholder text during development when they don’t have actual content ready yet
Before telling the reasons for why I needed a dummy file, I’ll first tell how I created a dummy file. I have created it in two ways now, one is using dd, another is using fallocate which I tried just today! Both of these I had to run in Linux. I also found out how to create dummy files in Mac OS and Windows OS too! See below
Works on Linux and Mac OS too:
$ dd if=/dev/zero of=dummy-file bs=1 count=10000
$ ls -alh dummy-file
That will create bs x count bytes, which is 1 x 10000 = 10000 bytes. You can
check more about the dd command in your OS by using man dd or dd --help
dd is what I used long ago, and I remember it being quite fast. But today I
noticed one more tool that was fast too, and apparently it’s really really
fast compared to dd. It’s called fallocate. This is how I used it
Works only on Linux:
$ fallocate -l 10K dummy-file
$ ls -alh dummy-file
For my use case, I created files of the size 1900MB.
Below is what I tried in MacOS, the mkfile command but it doesn’t seem to use
up disk space, based on what I see in df and du, but ls shows that the
file is big. May be use dd which will lower the disk space by consuming space.
I need to research more on this command 😅
$ mkfile -n 1g dummy-file
$ ls -alh dummy-file
Some asciinema demos in Linux and in Mac:
Linx:
Mac OS:
See below reference links for information on how to do it in Windows, and about where I learned about how to do it in Linux and Mac OS -
stackoverflow: Quickly Create a large file on a Windows system
stackoverflow: Quickly Create a large file on a Mac OS X system
stackoverflow: Quickly Create a large file on a Linux system
So, why did I even need dummy files in the first place? Well, today I needed a dummy file which is of a large size in a rabbitmq pod’s attached volume in kubernetes, so that it can use up disk space and when a lot of disk space is used, it will in turn trigger an alert from our alert system, which I wanted to see and test. Cool right? Putting pressure on your disk by creating large dummy files ;) Our alert was not showing info correctly and I wanted to fix that, so I was simulating the situation like this. And the alert was generated using Prometheus and sent to our Slack alerts channel using Alertmanager. If you are into infrastructure tools and monitoring, these are some well known tools to check out ;)
That’s all I had to tell about creating dummy files :)
Some more reference links that I used:
https://duckduckgo.com/?t=ffab&q=dummy+file+linux&ia=web
https://unix.stackexchange.com/questions/33629/how-can-i-populate-a-file-with-random-data
https://www.cyberciti.biz/faq/howto-create-lage-files-with-dd-command/
https://duckduckgo.com/?t=ffab&q=quickly+create+large+file+in+macos&ia=web&iax=qa