Karjala's blog

Someone please make for me a Linux program that will show RAM used by each process and all its child/descendant processes.

Here's my review of Void linux, a summary of the good and the bad I saw after using this flavour of Linux for well over a year now.

First, install etckeeper.

Then, create these two (executable) files:

/usr/local/bin/xbps-install

#!/usr/bin/env perl

use v5.38;

`whoami` eq "root\n" or die "Not root user";

!system('etckeeper pre-install') or die "Couldn't execute 'etckeeper pre-install'";
!system("/usr/bin/xbps-install", @ARGV) or die "Couldn't execute '/usr/bin/xbps-install @ARGV'";
!system('etckeeper post-install') or die "Couldn't execute 'etckeeper post-install'";

/usr/local/bin/xbps-remove

#!/usr/bin/env perl

use v5.38;

`whoami` eq "root\n" or die "Not root user";

!system('etckeeper pre-install') or die "Couldn't execute 'etckeeper pre-install'";
!system("/usr/bin/xbps-remove", @ARGV) or die "Couldn't execute '/usr/bin/xbps-remove @ARGV'";
!system('etckeeper post-install') or die "Couldn't execute 'etckeeper post-install'";

Then do sudo etckeeper init.

Then edit /etc/.gitignore to include files that shouldn't be versioned (such as /etc/resolv.conf).

Then create this executable file:

/etc/cron.daily/01-record_manual_packages

#!/bin/sh
xpkg -m > /etc/my_list_of_manual_pkgs

Then create this executable file:

/etc/cron.daily/02-etckeeper-daily-commit

#!/bin/sh
etckeeper commit "daily commit"

This setup is perfect.

All I had to do was use the Steam package from Flathub instead of the official Void package. And it works fine.

Apparently setting CGROUP_MODE to unified is not at all bad for you, so you should follow all the instructions contained in the incus/README.vodilinux file, including that.

If you still have problems starting Incus containers after that, like I did, your problem could be that you have the elogind service enabled. As everyone on IRC says, you shouldn't have it enabled. Disable it.

You may now ignore my previous #incus-tagged post.

1. I'll be able to debug programs that have problems and submit PRs to the author
2. I think I'll be able to follow documentation on how Linux works under the hood, where often code samples appear
3. I hope I'll be able to help in creating Void Linux packages for the software I use, increasing this way the availability of software for my favorite Linux distro
4. Be able to use C libraries from Perl scripts and create CPAN modules for them
5. Become able to use XS in Perl

I've started by starting to read beginners' books for C, not extremely sure that my IQ will be able to keep up with it though.

This is arcane and useful knowledge, so you should be grateful I'm giving it to you:

UPDATE my_table
    SET foo = my_table.foo + new_table.foo
    FROM (VALUES (1, 5), (2,6), (3,7)) AS new_table(id, foo)
    WHERE my_table.id = new_table.id;

This works optimally (in terms of duration per row updated) for a specific number of rows per SQL query, and slower as you move away from that number.

How to make your browser not show the annoying cookie banners on every site you visit:

Step 1: Install the uBlock Origin browser add-on (sorry Chrome users)

Step 2: uBlock Origin settings -> "filter lists" tab -> in the search box there type: cookie -> tick all the checkbox -> click on the apply settings button

I had written a Math paper which was not good enough to be published in a journal, yet I wanted to have proof of the date I wrote it on so I could post the paper on the web without other people later being able to question who first came up with the idea.

The way I thought was more correct to do this was to publish the paper's sha256 checksum on the Bitcoin blockchain. Posting the SHA on social media (such as x.com) was not enough, as paid members can edit their old posts.

I got in touch with BBRTJ, the maintainer of Bitcoin::Crypto, who was very helpful in teaching me how to use his module and achieving my aim.

The goal, he told me, was to include the SHA256 checksum as the comment (technically the 'NULLDATA') of a small bitcoin transaction.

1. I created a BTC address with Perl, using Bitcoin::Crypto
2. I transferred a very few dollars worth of BTC to this address
3. I found the transaction ID at mempool
4. I found the index number of the ouptut of the transaction that got crypto into my address, because this number together with the transaction ID are what form the UTXO
5. I used this UTXO as input (funds) in a new transaction that had two outputs: One output was the NULLDATA string (the "comment" that contains the SHA256 checksum of the PDF document), and the other was a "change" address of mine, which would receive the rest of the money from the UTXO (full amount minus transaction fee (around $1)).

Here are these steps in more detail, and with code:

Δεκεμβριανά 1944: Η ιστορία όπως έγινε κι όχι όπως θέλουν κάποιοι να την παραχαράξουν (video)

Δεκεμβριανά, Ώρα Ελλάδας, ΕΡΤ, Νικόλας Αγγελίδης, 4.12.2024 (video)

Podcast της ΚΝΕ - Επεισόδιο 37 | Πώς φτάσαμε στα Δεκεμβριανά; (video)

Πολλοί ιστότοποι που σερβίρουν πειρατικά αρχεία, όπως το pirate bay και το libgen, έχουν μπλοκαριστεί στην Ελλάδα απ' τους παρόχους internet σε επίπεδο DNS.

Επειδή αυτοί οι ιστότοποι σερβίρουν και πολλά νόμιμα αρχεία επίσης, καλό είναι να ξέρουμε πώς να παρακάμψουμε τους περιορισμούς αυτούς, χωρίς να πληρώσουμε συνδρομή σε VPN.

Ακολουθούν οι οδηγίες.

Το κείμενο δεν ειναι δικό μου, αλλά σας το παρουσιάζω:

Γιατί μας ενδιαφέρουν οι BRICS.

α. Οι BRICS ασχολούνται αποκλειστικά με τις διακρατικές σχέσεις, δεν επιβάλλουν δεσμεύσεις. Ο προστατευτισμός καθώς και άλλα πολιτικά συστήματα επιτρέπονται, αντίθετα με το σημερινό σύστημα που επιφέρει κυρώσεις. (Κούβα, Βενεζουέλα, Βολιβία, ...)

β. Αναπτύσσουν σε ένα οικονομικό σύστημα το οποίο βασίζεται στο χρυσό και άλλα αγαθά. Πράγμα που σημαίνει ότι υπάρχουν όρια και τα αποθεματικά δεν είναι πράσινα χαρτάκια που αντιστοιχούν σε αέρα κοπανιστό.

γ. Καθώς απαγορεύονται οι κυρώσεις μεταξύ τους, όπως και οι επεμβάσεις στα εσωτερικά κρατών μελών. Εμείς ως αναρχικοί / κομμουνιστές είμαστε σαφέστατα ΥΠΕΡ ΜΕ ΤΑ ΜΠΟΥΝΙΑ.

δ. Το νέο οικονομικό σύστημα άμεσα κόβει τα πόδια στις ΗΠΑ που πιθανόν να μην συνέλεθει ποτέ από το χτύπημα. Γιατί να επενδύσεις σε δολάριο όταν το άλλο νόμισμα έχει αντιστοιχία σε αγαθά; Δεν χρειάζεται καν να πιέσουν κανένα, μόνοι τους θα επενδύουν στο νέο νόμισμα.

Έχω να προτείνω ένα νέο, καλύτερο τρόπο να γίνονται οι διαγωνισμοί του δημοσίου:

Οι υποψήφιοι θα κατατάσσονται με βάσει το net worth τους (των ιδίων και των συγγενών τους μέχρι τεταρτου βαθμού - πρώτα ξαδέρφια δηλαδή), και οι πιο φτωχοί θα βλέπουν τις προσφορές που έχουν υποβάλει οι πιο πλούσιοι πριν υποβάλουν τη δική τους. Δηλαδή ο τρίτος πλουσιότερος θα βλέπει τις προσφορές του δεύτερου και του πρώτου, κ.ο.κ.

Έτσι οι πιο φτωχοί θα έχουν περισσότερες πιθανότητες να κερδίσουν δουλειές (και με την αξία τους!) και μάλιστα για καλή τιμή. Επίσης θα σπάσουν τα μονοπώλια και θα υπάρχει μεγαλύτερη ισοκατανομή του πλούτου.

Είναι το μόνο δίκαιο σύστημα και θα οδηγούσε σε χαμηλότερες τιμές και αύξηση της επιχειρηματικής δραστηριότητας.

Παρακαλώ τα σχόλιά και τις διαφωνίες σας.

Time::Piece is a core module in Perl, and very efficient. If you learn to use it, and care only about the UTC timezone, you can replace the DateTime module with it in your webapp. At least I did.

A few of my apps were taking an inordinate amount of time to launch (approximately 15 seconds). I was told I should prepend strace in the command-line that executes the app to see what was wrong.

A huge variety of fonts used everywhere to be able to view webpages properly is contained in the following four packages:

noto-fonts-cjk - Chinese, Japanese, Korean
noto-fonts-emoji
noto-fonts-ttf
noto-fonts-ttf-extra

(Found out on IRC)

Void Linux is one of the best Linux distributions out there: It's not maintained by a company and doesn't even have or want sponsors, so it'll stay on the side of users forever. It doesn't use systemd (that many users hate) as its init system, its package manager is very fast (maybe the fastest around), and it's extremely minimal in the amount of software installed by default (good for CPU & disk, the environment, and user-choice of alternatives), and it's a rolling stable distro.

The downside is that it's not for beginners. You'll often need to read documentation (Void's official documentation does a great job) to get things done, and also end-up asking questions in Void's IRC channel to Void's more experienced users.

I did (and still do) a lot of the asking, so I'm providing the most important information I learned there in this series of blog posts tagged #void_linux.

I created a function in Perl called pg_dt, that will convert PostgreSQL's datetime values into Perl's DateTime values and vice versa. This is useful both when you want to store DateTime values into the database, or want to convert the pg datetime/timestamp value from the database into a DateTime object value that Perl can use.

Incus is the replacement of LXD one should use. For some reason it won't work well on Void out of the box after a while, and incus start <container-name> might stop doing anything. How do we fix it?

Looking at /usr/share/doc/incus/README.voidlinux it suggests the following:

Some container configurations may require that the `CGROUP_MODE`
variable in `/etc/rc.conf` be set to `unified`.

One way to solve it is that. I did another solution however, which I found at this github issue. I did the following:

I created this Perl script, called enable_incus somewhere:

#!/usr/bin/env perl

use v5.38;

! -d '/sys/fs/cgroup/systemd' or say("Incus already enabled. Skipping."), exit;

system('sudo mkdir /sys/fs/cgroup/systemd');
system('sudo mount -t cgroup -o none,name=systemd systemd /sys/fs/cgroup/systemd');

say 'OK';

Then I edited /etc/sv/incus/run and added this line near the top:

/path/to/enable_incus

...so that my script gets executed just before incus is launched.

This fixed the problem.

Until now I've never managed to do it. Every time LXD complained that the backup I'm trying to restore is configured in an incompatible way with our system. Different bridge interface name, static IP is out of range of this machine's network pool, and other such stuff. So I was ending up creating new LXD containers from scratch instead of restoring my backups, whenever I re-installed Linux on my laptop.

Not this time though. The backup was a tar.gz file, so I uncompressed it, edited its two configuration files in there (backup/index.yaml and backup/container/backup.yaml) to my liking, re-compressed, and managed to import it.

Incus rocks!

Perl v5.40 introduced native true and false keywords. Unfortunately not all CPAN modules are ready to use them. One of those not yet ready is Mojo::Pg.

Normally you'd want to pass booleans to your queries as just 1's and 0's. However, since Mojo::JSON's true & false stringify to 1 and 0, my 5.38-using codebase is full of Mojo::Pg queries with Mojo::JSON's true and false as arguments.

This is a problem if I want to upgrade the perl interpreter of that project to Perl v5.40, because if I write "use v5.40;" in the file that contains those boolean keywords, Perl's builtin booleans will be used instead, which don't stringify to 1 and 0, but to 1 and the empty string, which can't be used by DBD::Pg in boolean fields and makes DBD::Pg throw an exception.

The solution I found was to subclass Mojo::Pg::Database, and wrap the query method, so that if Perl's builtin booleans are found, they are replaced in the query with native Pg booleans.

This is the subclass:

package Local::My::Pg::Database;

use v5.40;
use Mojo::Base 'Mojo::Pg::Database';

use DBD::Pg ':pg_types';

use experimental 'builtin';

sub query {
    my ($self, $query) = (shift, shift);
    my $cb = ref $_[-1] eq 'CODE' ? pop : undef;
    my @args = map { builtin::is_bool($_) ? { type => PG_BOOL, value => $_ ? 1 : 0 } : $_ } @_;

    return $self->SUPER::query($query, @args, $cb // ());
}

...which requires the Mojo::Pg object to be told to use it:

$pg->database_class('Local::My::Pg::Database');

This solved my problem.

The other module I had problems with on Perl v5.40 is Mojolicious::Plugin::OpenAPI, which doesn't let the builtin booleans to be used in the API spec. I wrote a patch for that, and might submit it to the author.

Other than those, Mojo::JSON does not stringify builtin booleans to booleans, but to 1 and "" unless Cpanel::JSON::XS is installed, in which case it works fine.

Have you found other CPAN modules that need to be updated for Perl v5.40's booleans?

This block of code is valid Perl:

if (my $var1 = calc1()) {
    say $var1;
} elsif (my $var2 = calc2()) {
    say "$var1, $var2";
}

As you can see, $var1, which is declared in the if clause, is visible inside the elsif clause too.

Perl never ceases to amaze me!

Σ' αυτό το σημείο, κι αφού η Άννα-Μισέλ παραιτήθηκε και το θέμα του spam δείχνει νά' χει ενδιαφέρον, να υπενθυμίσουμε ότι ο Κυριάκος Μητσοτάκης όταν ξεκίνησε τη πολιτική του καριέρα είχε πάρει τη λίστα των emails όλων των αποφοίτων του Κολλεγίου Αθηνών απ' το σάιτ του ΣΑΚΑ (σύλλογος αποφοίτων κολλεγίου αθηνών) και μας σπάμαρε ανελέητα για πολλά χρόνια.

Κατά παράβαση του νόμου που ήδη υπήρχε για προσωπικά δεδομένα, και τον οποίον είχε ψηφίσει και η ΝΔ, ο οποίος μας προστάτευε και από το σπαμ (το έβλεπε ως παράνομη επεξεργασία προσωπικών δεδομένων).

Έτσι: νόμους βγάζουνε για να τους τηρείς εσύ κι εγώ, όχι αυτοί. Γιατί εσείς είστε τα κορόιδα, ενώ αυτοί όχι!

*σημείωση: ξέρω ότι τα email τα πήρε απ' το σάιτ του ΣΑΚΑ, γιατί μου έστελνε στο saka@<some domain> που είχα χρησιμοποιήσει μόνο για να γραφτώ σ' αυτό το σάιτ.

Η ΝΔ δεν τα πήγαινε καλά με το νόμο για σπαμ όμως, ούτε αργότερα. Το Μάιο 2018, όταν τέθηκε σε εφαρμογή ο νόμος GDPR για τα προσωπικά δεδομένα, η ΝΔ (όπως και όλες οι εταιρείες) όφειλε να λάβει opt-in επιβεβαίωση απ' τα μέλη της αν ήθελε να συνεχίσει να τους στέλνει ενημερωτικά emails, ευχές στις γιορτές, κλπ. Δεν τό' κανε. Οι βουλευτες της συνέχισαν να στέλνουν τακτικά στα μέλη της ΝΔ χωρίς κανείς τους να πάρει την απαιτούμενη συγκατάθεση.

Κάποτε ο κόσμος ήταν καλός και κυβερνούσαν οι καλοί, αλλά σε κάποια φάση ήρθαν οι κακοί στην εξουσία με ύπουλες μεθοδεύσεις. Αυτό είχε σα συνέπεια ο κόσμος να πάει να καταστραφεί και μόνος τρόπος να σωθεί είναι να ξανάρθουν στα πράγματα οι καλοί. Φυσικά αυτό δε γίνεται με δημοκρατικές μεθόδους, γιατί οι κακοί έχουν φροντίσει να αποβλακώσουν το κόσμο, οπότε αναγκαστικά θα έρθουμε στα πράγματα πραξικοπιματικά.

Ετοιμαστείτε.

A bunch of statistics showing Greece's true position in the world.

This site offers a programming challenge for every day of December until Christmas. It's really interesting, and fun to try to solve.

I seem to have gotten the hang of it.

Welcome. As you will hopefully find out in this blog, Perl is the best language in the world.

#!/usr/bin/env perl

print "Hello, world!\n";