I had installed Windows 10 successfully. While messing around with my other Linux partitions, a partition delete went awry and on booting I was dropped into a GRUB rescue prompt. What I wanted was the Master Boot Record to be restored to boot into Windows 10.
On another computer, I downloaded a Windows 10 ISO and created a bootable Windows recovery USB disk as described here.
I booted with this USB disk, chose Troubleshoot -> Advanced Options -> Command Prompt.
Bootchart is a tool that can be used to visualize and analyze the boot process. It is a shell script that is run by the kernel in the background. It analyzes all the information and renders a chart that makes it easy to understand the CPU, disk and services that run at boot. This can be useful to understand your system or find bottlenecks that might be making your system to boot slowly.
Installing Bootchart is easy:
$ sudo apt install bootchart
That is it! It will automatically run every time the system is booted up. The chart it generates is stored in /var/log/bootchart as a PNG file.