Websites -- like hackernews/ycombinator -- free code hosting, on gogs  -- privacy

Linux System and Network Performance Monitoring/Analysis

general performance analysis --

traceroute and mtr --

ss -- 

Tech -- self-hosted git
irc server admin
dns records / domain name registration
ubuntu service management
Pure Bash Bible -

GNU/Linux, *NIX Sysadmin
Debian Stretch Administrator's Handbook:
Arch sysadmin:

Mailserver admin

Postfix architecture overview:
Antomy of Postfix: