Z3 is a theorem prover developed at Microsoft research and available as a dynamically linked C++ library in Debian-based distributions. While the library is a whopping 16 MB, and the solver is a tad slow, it’s permissive licensing, and number of tactics offered give it a huge potential for use in solving dependencies in a wide variety of applications. Z3 does not need normalized formulas, but offers higher level abstractions like atmost and atleast and implies, that we will make use of together with boolean variables to translate the dependency problem to a form Z3 understands. ... Read more

This is an edited copy of an email I sent to provide guidance to users of apt-key as to how to handle things in a post apt-key world. The manual page already provides all you need to know for replacing apt-key add usage: Note: Instead of using this command a keyring should be placed directly in the /etc/apt/trusted.gpg.d/ directory with a descriptive name and either “gpg” or “asc” as file extension ... Read more

APT 2.2.0 marks the freeze of the 2.1 development series and the start of the 2.2 stable series. Let’s have a look at what changed compared to 2.2. Many of you who run Debian testing or unstable, or Ubuntu groovy or hirsute will already have seen most of those changes. New features Various patterns related to dependencies, such as ?depends are now available (2.1.16) The Protected field is now supported. ... Read more

Yesterday I got a fresh new Pixel 4a, to replace my dying OnePlus 6. The OnePlus had developed some faults over time: It repeatedly loses connection to the AP and the network, and it got a bunch of scratches and scuffs from falling on various surfaces without any protection over the past year. Why get a Pixel? Camera: OnePlus focuses on stuffing as many sensors as it can into a phone, rather than a good main sensor, resulting in pictures that are mediocre blurry messes - the dreaded oil painting effect. ... Read more

Sporting a beautiful 10.1" 1920x1200 display, the Lenovo IdeaPad Duet Chromebook or Duet Chromebook, is one of the latest Chromebooks released, and one of the few slate-style tablets, and it’s only about 300 EUR (300 USD). I’ve had one for about 2 weeks now, and here are my thoughts. Build & Accessories The tablet is a fairly Pixel-style affair, in that the back has two components, one softer blue one housing the camera and a metal feeling gray one. ... Read more

Ubuntu “Focal Fossa” 20.04 was released two days ago, so I took the opportunity yesterday and this morning to upgrade my VPS from Ubuntu 18.04 to 20.04. The VPS provides: SMTP via Postfix Spam filtering via rspamd HTTP(S) via nginx and letsencrypt (certbot) Weechat relay OpenVPN server Shadowsocks proxy Unbound recursive DNS resolver, for the spam filtering I rebooted one more time than necessary, though, as my cloud provider Hetzner recently started offering 2nd generation EPYC instances which I upgraded to from my Skylake Xeon based instance. ... Read more

After brewing in experimental for a while, and getting a first outing in the Ubuntu 19.10 release; both as 1.9, APT 2.0 is now landing in unstable. 1.10 would be a boring, weird number, eh? Compared to the 1.8 series, the APT 2.0 series features several new features, as well as improvements in performance, hardening. A lot of code has been removed as well, reducing the size of the library. ... Read more

If you have ever used aptitude a bit more extensively on the command-line, you’ll probably have come across its patterns. This week I spent some time implementing (some) patterns for apt, so you do not need aptitude for that, and I want to let you in on the details of this merge request !74. so, what are patterns? Patterns allow you to specify complex search queries to select the packages you want to install/show. ... Read more

In the previous post about setting up a email server, I explained how I setup a forwarder using Postfix. This post will look at setting up Dovecot to store emails (and provide IMAP and authentication) on the server using GPG encryption to make sure intruders can’t read our precious data! Architecture The basic architecture chosen for encrypted storage is that every incoming email is delivered to postfix via LMTP, and then postfix runs a sieve script that invokes a filter that encrypts the email with PGP/MIME using a user-specific key, before processing it further. ... Read more

This week, I’ve been working on rolling out mail services on my server. I started working on a mail server setup at the end of November, while the server was not yet in use, but only for about two days, and then let it rest. As my old shared hosting account expired on January 1, I had to move mail forwarding duties over to the new server. Yes forwarding - I do plan to move hosting the actual email too, but at the moment it’s “just” forwarding to gmail. ... Read more