Alright, kdump that mysterious feature that saves your bacon when your Linux system goes belly up. But before we dive in, let me ask you a question: have you ever wondered how much memory you need for kdump? Well, wonder no more! In this article, I’m going to show you the secret sauce for estimating kdump size with ease and grace.

To start what is kdump? It’s essentially a crash dump utility that allows your system to recover from kernel panics or other catastrophic events by booting into a separate memory space, capturing the state of the system at the time of failure, and saving it to disk for analysis. Pretty cool, right?

But here’s the thing kdump requires some extra memory to do its job properly. And that’s where our little trick comes in handy!

Introducing…the kdumpctl estimate command! This magical tool helps you calculate the recommended crashkernel value for your system based on various factors like kernel size, modules, initramfs, and LUKS encrypted target memory requirements (if applicable).

Here’s how it works:

1. Run `kdumpctl estimate` in a terminal window. This will print out the estimated crashkernel value that you should use for kdump.

2. Take note of this number it’s your new best friend!

3. Configure your system to use this recommended crashkernel size by editing your kernel command line options (usually found in /etc/default/grub). Add the following line: `crashkernel=` and save the changes.

4. Reboot your system, and voila! Your kdump is now ready to roll with its new memory allocation.

But wait what if you’re using LUKS encryption for your kdump target? In that case, you need to add an extra step: calculate the required size for your encrypted target by running `kdumpctl estimate` again and looking at the “LUKS required size” value. This is the amount of memory needed to store the encrypted data during a crash dump.

5. Add this LUKS required size to your kernel command line options, like so: `crashkernel=:` (replace and with the appropriate values).

And that’s it! You now have a fully configured kdump system with enough memory to handle even the most catastrophic events.

But wait what if your RAM size is larger than 2GB? In that case, you can reserve 128MB of memory for crashkernel by running `echo “vmalloc=512M” /etc/sysctl.conf` and then rebooting the system. This will ensure that kdump has enough space to do its job properly without interfering with your regular system operations.

Finally, you can verify that the kernel has reserved the requested memory area for crashkernel by running `dmesg | grep -i crash`. If everything is working correctly, you should see a message like this: “Reserving 64MB of memory at 800MB for crashkernel (System RAM: 1023MB)”.

And that’s it! You now have a fully configured kdump system with enough memory to handle even the most catastrophic events. So go ahead and sleep soundly, knowing that your Linux machine is protected by this magical tool called kdump.