How To Become A Hacker by Eric Steven Raymond
The Linux Command Line by William Shotts
SSL/TLS related
The definitive guide to using the OpenSSL command line for configuration and testing, by Ivan Ristić:
https://www.feistyduck.com/books/openssl-cookbook/
Se vi interessa approfondire ulteriormente potete acquistare BULLETPROOF TLS AND PKI dello stesso autore.BSD related links
A weekly podcast and "the place to B...SD":