Learning to be good at thinking, thinking, thinking.

What’s up? Recently, when I use yay -Syu to update the software packages, it always prompts that a package cannot be updated and prompts are warning: could not fully load metadata for package and error: failded to prepare transaction (invalid or corrupted package). It’s time to solve this annoying problem. Remove first Try to remove it firs... Read More

Table Here’s a table of the email server ports. Ports Protocal Security Authentication Description 25 SMTP None AUTH Outgoing Messages 587 SMTP None or TLS STARTTLS Outgoing Messages 465 SMTP ... Read More

Introduction Have you ever thought about setting up your own email server, but then left it behind. However, setting up a email server is not complicated. In this article, we will build it step by step from scratch. Here we will need the following environments: Nginx - an lightweight and open-source web server to offer low memory usage and... Read More

What’s up? Recently, I encountered a weird problem. When I used SSH to connect to a Linux server, the connection was immediately interrupted, and such a message appeared: free(): invalid next size (fast), screenshot as below image: Troubleshooting After that, I tried to connect using another Linux computer and still had the same problem. Bu... Read More

MD-family The MD family of hashing algorithms were designed by Ron Rivest during the late 1980’s and early 1990’s. MD actually stands for “Message Digest”. MD2 It was optimized to run on 8-bit computers and generates a 128-bit hash value the hashes are generally displayed as hexadecimal string which is 32 characters long. This hash exhibits f... Read More

Generating RSA key pair OpenSSL can generate several kinds of public/private keypairs. RSA is the most common kind of keypair generation. Generating an RSA private key You can generate a 2048-bit RSA private key with the following commands: openssl genpkey -algorithm RSA -out rsa_private.pem \ -pkeyopt rsa_keygen_bits:2048 or openssl ge... Read More

Abstract and concrete are opposite concepts, many times we just know what they mean, but don’t really understand them. So today let us get to know them again and have a clearer and deeper understanding of them. Abstract An abstract is a brief summary of one or more things, there are two important points here: From one or more things Find... Read More

Table Here’s a table of the vowels in English. Symbol Word Transcription More Examples [i:] fee [fi:] she, cream, believe, receive, heed, meet [ɪ] fit [fɪt] hit, income, definition, been (for some) [u:] boot [b... Read More

Table Here’s a table of the consonants in English. Manner Voicing Symbol Word Transcription More Examples Plosives/Stops Voiceless [p] pat [pæt] put, post, apart, spar     [t] tie [taɪ] type, stem, nast... Read More

& ampersand, epershand or and @ at % percent / slash, forward slash, oblique, solidus, stroke or division \ backslash . period(US), full stop(UK) or dot * asterisk, multiplication or star ~ tilde _ underscore + plus - minus, hyphen or dash = equal... Read More