week 44, 2019

How to locate and close an open port in Linux

So you're a network administrator and you have a number of Linux machines in your data center. You've found some odd traffic bouncing about your network and your curiosity is piqued. Is it possible that traffic is making use of an open port on a machine? If so, where's the port and how do you close it?

On those Linux machines, the task is actually pretty simple. I want to show you how to locate an open port and close it. I'll be demonstrating on Ubuntu Server 18.04, although the process will be similar on many distributions—the only difference being how you close the port.

Source: How to locate and close an open port in Linux, an article by Jack Wallen.

See also Use nmap to find machines and open ports and What's listening on port 8080.

The complicated truth about a cat’s purr

We think we know what a cat’s purr means.

It is arguably the most recognisable sign of animal contentment: a pleasurable rasp that erupts whenever a cat is tickled or petted, the soundtrack to countless sessions sprawled on an owner’s lap.

But that’s not quite the full story. There is a lot more going on with the cat’s purr than you might reasonably expect.

Source: The complicated truth about a cat’s purr, an article by Stephen Dowling.

7 Practical Tips for Cheating at Design

It’s easy to throw your hands up and say, “I’ll never be able to make this look good, I’m not an artist!” but it turns out there are a ton of tricks you can use to level up your work that don’t require a background in graphic design.

Here are seven simple ideas you can use to improve your designs today.

Source: 7 Practical Tips for Cheating at Design, an article by Adam Wathan & Steve Schoger.

The Night Fire

Harry Bosch and LAPD Detective Renée Ballard come together again on the murder case that obsessed Bosch's mentor, the man who trained him.

In the evening I started in The Night Fire, a Renée Ballard and Harry Bosch novel by Michael Connelly.

Deploying Docker Securely

In this post, I will outline steps you can take to securely deploy a docker environment. This assumes you are using Docker daemon on hardware running Linux that you administer. Our main goal is to prevent container escapes and multiple container breaches in the event that a single container is compromised.

Source: Deploying Docker Securely, an article by Charlie Belmer.

Using top on macOS

In the afternoon I noticed that my Mac mini 2014 running macOS Mojave was running slow. Even typing was sluggish. So I typed the following in an open terminal:

top -u

to find the culprit, which turned out to be Thunderbird, using 67% CPU.

Note that top -u is an alias for

top -o cpu -O time

meaning it sorts first on the CPU column, and on the time column next.

Let's Encrypt

In the evening I installed a new operating system image on the virtual private server (VPS) that hosts Plurrrr. It was originally running on an old CentOS installation but this time I decided to use Ubuntu.

The main reason for the update was to switch to HTTPS for Plurrrr, which turned out easier than I expected thanks to Certbot.