Lester Guerzon guerzon

Linux Engineer

guerzon / openssl_commands.sh

Last active February 18, 2024 23:48

Useful OpenSSL comands for testing, troubleshooting, and information gathering


	# Test an SSL connection
	openssl s_client -connect <IP>:<PORT>

	# Test if SSLv3 is supported
	# Expected result if TLSv1.0 is not supported: ssl handshake failure
	openssl s_client -connect <IP>:<PORT> -ssl3

	# Test if TLSv1.0 is supported
	# Expected result if TLSv1.0 is not supported: ssl handshake failure

guerzon / verify_ciphers.sh

Last active December 18, 2019 03:05

Useful script to test cipher suite support of services running SSL/TLS.

	#!/usr/bin/env bash
	# Usage: ./verify_ciphers.sh IP:PORT
	# Credits: http://superuser.com/a/224263/204745

	# OpenSSL requires the port number.
	SERVER=$1
	DELAY=1
	ciphers=$(openssl ciphers 'ALL:eNULL' \| sed -e 's/:/ /g')

	echo Obtaining cipher list from $(openssl version).

guerzon / ansible references

Last active November 6, 2019 11:52

List of useful internet resources for ansible

	## Important Documentation

	Documentation: https://docs.ansible.com/ansible/latest/index.html
	Modules: https://docs.ansible.com/ansible/latest/modules/modules_by_category.html
	Community: https://docs.ansible.com/ansible/latest/community/index.html

	## Other resources

	Ansible for the Windows Admin: https://www.youtube.com/watch?v=ZI20Y10OKd0

guerzon / install_jenkins_plugin.sh

Created February 1, 2019 01:44 — forked from chuxau/install_jenkins_plugin.sh

	#!/bin/bash

	set -e

	UPDATES_URL="http://updates.jenkins-ci.org/download/plugins/"

	if [ $# -lt 2 ]; then
	echo "USAGE: $0 plugin-list-file destination-directory"
	exit 1
	fi

guerzon / pam_tally_reset.txt

Created November 14, 2018 01:23

Reset pam module login counters

	### On RHEL5 servers ###
	1. Check the login failure count
	pam_tally --user username
	2. Reset the login failures
	pam_tally --user username --reset
	3. Retry logging in.

	### On RHEL6 and RHEL7 servers ###
	1. Check the login failure count
	pam_tally2 --user username

guerzon / latency.txt

Created October 29, 2018 01:55 — forked from jboner/latency.txt

Latency Numbers Every Programmer Should Know

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD