Useful-Links

Linux

http://www.thegeekstuff.com/2010/11/50-linux-commands/

http://www.thegeekstuff.com/2009/06/15-practical-crontab-examples/

http://www.tecmint.com/ip-command-examples/

Games/CTF

https://www.hackthis.co.uk/levels/

https://www.codingame.com/multiplayer/clashofcode

https://www.vulnhub.com/

https://www.root-me.org/en/Challenges/

https://immersivelabs.online/signin

https://www.hackthebox.eu/invite

Tech News Websites

https://hackernoon.com/

https://thehackernews.com/

Sysadmin

https://github.com/trimstray/test-your-sysadmin-skills/blob/master/README.md#guru-sysadmin

http://thelazyadministrator.com/

https://foxdeploy.com/

Programming

https://tutorialedge.net/python/concurrency/getting-started-with-asyncio-python/

https://linustechtips.com/main/topic/301263-ultimate-programming-resources-thread/

https://www.flashcardmachine.com/c-programming.html

https://realpython.com/

Video Resources

http://www.securitytube.net/

https://infosec-conferences.com/best-def-con-talks/

Other Github collections

https://github.com/ctfs/

https://github.com/apsdehal/awesome-ctf

https://github.com/Kickball/awesome-selfhosted

Penetration Testing

https://highon.coffee/blog/penetration-testing-tools-cheat-sheet/

http://www.0daysecurity.com/penetration-testing/enumeration.html

https://medium.com/@johntroony/a-practical-overview-of-stack-based-buffer-overflow-7572eaaa4982

https://liveoverflow.com/

https://www.owasp.org/index.php/OWASP_Cheat_Sheet_Series

https://highon.coffee/blog/penetration-testing-tools-cheat-sheet/

Hak5 Channel https://www.youtube.com/channel/UC3s0BtrBJpwNDaflRSoiieQ

DEFCON Channel https://www.youtube.com/channel/UC6Om9kAkl32dWlDSNlDS9Iw

LiveOverflow Channel https://www.youtube.com/channel/UClcE-kVhqyiHCcjYwcpfj9w

Research Blogs

http://chrissanders.org/

DevOps

https://github.com/collections/devops-tools