Linux

Sometimes it happens that vagrant hangs during boot of your virtual image. Right after typing: ``bash $ vagrant up ` It hangs for a long time and then finally throws: `bash [default] Failed to connect to VM! Failed to connect to VM via SSH. Please verify the VM successfully booted by looking at the VirtualBox GUI. `` If you open VirtualBox you'll see that the virtual machine preview shows a black screen with kernels to choose from. This is GRUB requiring user input to boot further. Here's how to fix that.

Unfortunately the Linux DNS resolver has no direct support for detecting and doing failovers for DNS servers. It keeps feeding requests to your primary resolving nameserver, waits for a configured timeout, attempts again, and only then tries the second nameserver. This typically means nearly 30s delay for all request as long as your primary nameserver is unreachable. It doesn't learn to directly target your secondary nameserver so long as there is trouble. Even with the most optimal configuration, the delay will still be measured in seconds per request. For many requests, that's many more seconds. I wanted to solve this.

I recently had an annoying encounter with the error message: `Too many authentication failures for root`. I found out this can be caused because you've hoarded too many SSH keys :) So serves me right, but let's see what happens exactly.

If something weird is happening, you want to know everything that's going on on a server, as fast as possible. At these times, you will be very happy to have a simple alias `wtf` installed that you can type immediately after logging into a server, and see all that it's busy with.

> "Simplicity is prerequisite for reliability." [Edsger W. Dijkstra](https://www.cs.utexas.edu/users/EWD/transcriptions/EWD04xx/EWD498.html) As our experience grows, we learn from past mistakes and discover what's truly important in reliable systems. When designing systems, simplicity is an often heard mantra, but it isn't getting applied nearly as much as spoken of. I'm guilty of this too. I think it's mainly because engineers love to, well, engineer :) and will naturally try to [outsmart problems by throwing more tech at it](https://teddziuba.com/2010/12/the-3-basic-tools-of-systems-engineering.html).