iptables rules are all lost when the PC is shutdown. This post shows how to permanently enable the added rules even after restarts. The post uses systemctl startup script introduced here. Suppose that you want to add this rule: -A INPUT -i docker0 -j ACCEPT -p tcp --dport 1234. Step

Sometimes you need to quickly fix an npm package without waiting for a new version to be published which usually takes time. In this post, I will show you how to do that with yarn 2, without using any additional tools. For yarn 1 users, please use the patch-package package

Problem Sometimes, the OS open a new VSCode instance when you want to open a directory (via xdg-open) with the default file manager (such as nautilus). Many users have claimed about this issue: #41037, #80499, #44344, archlinux, ... Background The OS chooses an application when opening a file (directory is a

This post includes the following content: * Create a certificate signing request (CSR) * Create your own certificate authority (CA) certificate to self-sign the CSR * Test the signed certificate with chrome and curl Part 1: Create a certificate signing request (CSR) Step 1: Create a private RSA key openssl genrsa -out server.

In this post, I will show 3 ways to use apt in a private server (a server that does not have direct internet access). Method 1: Download the .deb files and install them manually Adding  --print-uris to the apt command will print the URLs to download necessary .deb files. You

This post shows you how to SSH through a proxy server. Prerequisites The local client is required to have OpenBSD netcat installed. There are 2 versions of netcat. Traditional netcat and OpenBSD netcat. This tutorial explicitly requires OpenBSD netcat. Traditional netcat won't work. See their difference here. In macOS: # nc

Running (training) legacy machine learning models, especially models written for TensorFlow v1, is not a trivial task mostly due to the version incompatibility issue. This post will show the compatibility table with references to official pages. The general flow of the compatibility resolving process is * TensorFlow → Python * TensorFlow → Cudnn/Cuda

Initially, when you create a Kubernetes cluster in AWS (or we call EKS = Elastic Kubernetes Service), only the creator can have full access to the cluster. Other AWS users, even with the Administrator access of the AWS organization, can see the cluster name and several general configurations, but cannot access

You have your own AWS account (in your organization), and several accounts in client organizations. This post shows you how to manage all accesses in a single account. So that you do not have to log out and log in every time. Some values used in this post: * Your organization

For security purposes, some browsers have a minimum font setting larger than zero by default in a specific condition. When your website has text with a font size smaller than 10px or 12px, you should expect that that text might be rendered as 10px (even you set it as smaller,

It sometimes happens that although you have already set up your private/public key, you still cannot get connected to the remote server with ssh. In practice, there is an uncountable number of reasons: firewall, server configuration that restricts external access, ... The recommended method to find the reason is to

This article explains the order of the NULL value in the ORDER BY clause in sql, with reference to the official document for each dialect. The default behavior The following SQL dialects consider NULL as the largest value (the last position in ascending order of any value type): PostgreSQL, Oracle.

If you are using Python 3.9, you might get the following error when running the add-apt-repository command: Traceback (most recent call last): File "/usr/bin/add-apt-repository", line 191, in if not sp.add_source_from_shortcut(shortcut, options.enable_source): File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line

TLDR; Go to /Library/Developer/CoreSimulator/Profiles/Runtimes and delete your unused simulators. To quickly open the directory. There are 3 ways: * From the terminal, run open /Library/Developer/CoreSimulator/Profiles/Runtimes. * In Finder, press Cmd + shift + g, paste the directory path. * In Finder, select Go menu, select Go to

Fundamental concepts * In general, x/ left suffices refer to the horizontal distance, while y/ top suffices refer to the vertical one. * Viewport is the area/portion of the web page (precisely speaking, the nearest iframe) that we can see on the screen. Imagine a web page is an infinite landscape,

TLDR; * z z or z .: move the current line to the center (in German: zentrum) of the viewport. * z t: move the current line to the top of the view port. * z b: move the current line to the bottom of the view port. * ctrl y: move the viewport up

Check the current swap space configuration Use swapon --show or free -h. If swap space is not used, swapon --show will output nothing, while free -h outputs with 0 bytes for swap, for example: total used free shared buff/cache available Mem: 1.9Gi 214Mi 138Mi 2.0Mi 1.6Gi

Definition What is event bubbling? Most events attached to the DOM node do propagate (bubble/capture). In other words, when an event is triggered * It first goes from the most parent event (i.e., the window object) to the lowest descendant. This phase is called capturing. Note: IE does not

I made this post to summarize several critical practices in the PR review process based on my experience. The list includes only essential rules, rather than general ones. Feel free to pick up and adopt any of them to your team. Hope that they can be helpful. -------------------------------------------------------------------------------- P1. Avoid

In this post, I will share my coding convention for my React projects. If you think they are useful for your project especially at the initial setup stage of the project, please feel free to pick up any of them and apply to your team. Although these rules are rather

From ES6, there are Proxy [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy] and Reflect [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect] classes that allow us to customize the objects at several language levels. For example property retrieval, assignment, iteration, function

Check if a value is an array type. To check whether an object is array type, use Array.isArray() [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray] , instead of instanceof Array. Reason: instanceof Array does not work across realms ( window, iframe). Check here [https://stackoverflow.

TLDR; * With an ES6 Map, use for (const [key, value] of myMap), this is equivalent to for (const [key, value] of myMap.entries()). * With an ES6 Set, use for (const value of mySet), this is equivalent to for (const value of mySet.values()). * With an array, use for (const value

In Javascript, an object's property falls into exactly one of two categories (not both, not none of them): data property, accessor property (ECMA [https://tc39.es/ecma262/#sec-object-type]). Definition Regardless of with or without your explicit definition, all object's properties have their associated property descriptor, which has the following properties.

How does the new operator work in Javascript, when for example, calling new MyClass(...params)? * Step 1: create a new object by Object.create(MyClass.prototype). * Step 2: call MyClass's constructor function (the MyClass itself if and only if (iff) it is a function) with this set as the object