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Prerequisites

This page lists some simple commands, code snippets and questions that attendees should understand before coming to class.

Linux command line

  • How to list running processes?
    • How to kill/terminate a process?
  • Find all TCP and UDP listeners on Linux system.
  • What is a difference between process and thread?
  • How to redirect output of one program into input of another in Unix-like system?
  • What is the purpose of /var, /home, /bin, /mnt and /srv directories in Linux filesystem?
    • What is the fundamental difference between /srv, /mnt and /opt?
  • How to set an IP address to network interface from command line without editing any files or restarting any services?
  • What is a regular expression?
  • What is syslog?
    • Where are log files usually located on a Linux system?

Know this stuff

Explain the following commands and scripts

FILE=/etc/apt/apt.conf.d/99force-ipv4
[[ -f $FILE ]] ||  echo 'Acquire::ForceIPv4 "true";' | sudo tee $FILE

for src in et/open ptresearch/attackdetection oisf/trafficid; do suricata-update list-enabled-sources | grep $src || suricata-update enable-source $src >> /vagrant/provision.log 2>&1 ; done

#!/bin/bash

if [[ ! -f /var/run/generator-2 ]]; then
  while : ; do curl -s https://www.facebook.com/ > /dev/null 2>&1 ; sleep 10 ; done & sleep 1; echo $! > /var/run/generator-1
  while : ; do curl -s http://testmyids.com > /dev/null 2>&1 ; sleep 10 ; done & sleep 1; echo $! > /var/run/generator-2
  while : ; do curl -s http://tumblr.com > /dev/null 2>&1 ; sleep 10 ; done & sleep 1; echo $! > /var/run/generator-3
fi

What is the difference between these two echo statements?

export myname="CDMCS"
echo "$myname"
echo '$myname'

Scripting

Explain the following commands and scripts

import json
def task(data={"foo":"bar"}):
    return json.dumps(data).encode(encoding="utf-8") + "\n".encode(encoding="utf8")

echo foo | python -c "import sys; print(sys.stdin.read())"