Explanation DKIM (DomainKeys Identified Mail) in all details DKIM (DomainKeys Identified Mail) is a system that lets your official mail servers add a signature to headers of outgoing email and identifies your domain’s public key so other mail servers can verify the signature. As with SPF (Sender Policy Framework helps keep your mail from being considered spam. It also lets mail servers detect when your mail has been tampered with in transit. Networking Security
SPF - Sender Policy Framework Email Message Structure To understand how SPF (Sender Policy Framework) and DKIM works is to know the difference between email envelope and email header . Short Definition: Sender Addresses in E-Mails Like paper mail letters, e-mail messages have at least two kinds of sender addresses: one on the envelope and one in the letterhead. The envelope sender address (sometimes also called the return-path) is used during the transport of the message from mail server to mail server, e. Networking Security
What is email envelope and email header The key for understand smtp protocol is learn, what is difference between email envelope and email header. Another words, what is email envelope vs email header. Networking Security
The most important Redis data structures you must understand Redis is the world's most popular in-memory data structure server. In order to make good use of it, we need to understand its basic data structures first. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs and geospatial indexes with radius queries. Linux
Python Dictionaries on Steroids with Python-benedict Python-benedict is a powerful Python library that extends the capabilities of Python's built-in dictionary (or dict) class. The library enables you to easily access, search, and modify nested values, manipulate and transform data, and convert various formats to and from dictionaries. As the dictionary is one of the most commonly used data structures in Python, this library could be a potential boost to productivity. Python Development
Webserver in bash - execute bash command Do you want a quick, dirty, and unsafe way to execute commands to your Linux box over HTTP? You can use the following hack! I don't recommend using this for a production system or something more important than a hobby project. Linux Bash
Nginx TLS TCP Proxy server for tcp upstream servers What is SSL Termination SSL/TLS termination means that NGINX acts as the server-side SSL/TLS endpoint for connections with clients: it performs the decryption of requests and encryption of responses that backend servers would otherwise have to do. The operation is called termination because NGINX closes the client connection and forwards the client data over a newly created, unencrypted connection to the servers in an upstream tcp servers. In release R6 and later, NGINX performs SSL/TLS termination for TCP connections as well as HTTP connections. Web Servers Security
Bash Parameter Substitution Table 1: Bash Parameter Substitution Variable Description ${parameter:-defaultValue} Get default shell variables value ${parameter:=defaultValue} Set default shell variables value ${parameter:?"Error Message"} Display an error message if parameter is not set ${#var} Find the length of the string ${var%pattern} Remove from shortest rear (end) pattern ${var%%pattern} Remove from longest rear (end) pattern ${var:num1:num2} Substring ${var#pattern} Remove from shortest front pattern ${var##pattern} Remove from longest front pattern ${var/pattern/string} Find and replace (only replace first occurrence) ${var//pattern/string} Find and replace all occurrences ${! Linux Bash Development
BASH - Check IP is in range of ip pools I have a list of IPs in MAXCDN_ARRAY to be used as whitelist. I want to check if a specific IP address is in range in this array. How can I structure the code so that it can compare all IPs in the array and say the specific IP in in range of this list or not? GrepCIDR You can use grepcidr to check if an IP address is in a list of CIDR networks. Linux Bash Development
Pyhon Lru Cache with time expiration In this tutorial, you'll learn: How to expand the functionality of the @lru_cache decorator and make it expire after a specific time Python Development
How to Test an SMTP Server with Telnet command line How to test SMTP and IMAP servers using the telnet command-line Linux Networking Windows
Nginx Location Priority Manual The location directive within NGINX server block allows to route request to correct location within the file system. The directive is used to tell NGINX where to look for a resource by including files and folders while matching a location block against an URL. In this tutorial, we will look at NGINX location directives in details. Linux Networking Web Servers
