linux

• IPtables

• Netplan

• Bash

  • Ejemplo bucle For
  • Ejemplo bucle While infinito

• Shell-script

  • Function
  • if - elif - else - fi
  • Petición parámetros
  • case

• Diff

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IPtables

sudo apt-get install iptables-persistent netfilter-persistent

vi /etc/iptables/rules.v4 \

# Generated by iptables-save v1.6.1 on Thu Mar 5 11:22:52 2020
*filter
:INPUT DROP [67:7427]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [20:5468]
:LOGGING - [0:0]
-A INPUT -i lo -j ACCEPT
-A INPUT -d 127.0.0.0/8 ! -i lo -j REJECT --reject-with icmp-port-unreachable
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s 192.168.14.0/25 -p tcp -m tcp --dport 22 -m comment --comment "SSH" -j ACCEPT
-A INPUT -p icmp -m comment --comment "PING" -j ACCEPT
-A INPUT -j LOGGING
-A LOGGING -m limit --limit 2 /min -j LOG --log-prefix "IPTables:DROP: "
-A LOGGING -j DROP
COMMIT
# Completed on Thu Mar 5 11:22:52 2020

cat /etc/rsyslog.d/40-iptables.conf \

:msg, regex, "iptables:" -/var/log/firewall.log
& ~

sudo /etc/init.d/rsyslog restart

Netplan

vi /etc/netplan/99-netcfg.yaml

network: version: 2 renderer: networkd ethernets: ens192: dhcp4: no dhcp6: no addresses: - 192.168.1.100/24 gateway4: 192.168.1.1 nameservers: addresses: - 9.9.9.9 - 8.8.8.8

netplan apply

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Bash

Ejemplo Bucle For

for i in $(ls -a); do echo "fichero ${i}"; done

Ejemplo Bucle While infinito

while [ true ]; do echo "hello world\n"; sleep 3; done

---

Shell-script

#!/bin/bash

ECHO=$(which echo) CAT=$(which cat) NMAP=$(which nmap) RM=$(which rm) DIFF=$(which diff) ...

Function

function Usage () { ${ECHO} -e "SYNTAX ERROR: ${0} [opcion1|opcion2] \n" exit 1 }

if - elif - else - fi

Verificamos los parametros si son nulos, y si primer parametro contiene valor correcto.

if [[ -z ${1} ]] || [[ -z ${2} ]] ; then Usage elif [[ "${1}" != "opcion1" ]] && [[ "${1}" != "opcion2" ]] ; then Usage else accion="${1}" nombre="${2}" fi

Si fichero existe entonces lo borramos:

if [[ -f "${nombreFichero}" ]] ; then ${RM} ${nombreFichero} fi

Petición parámetros

${ECHO} "Introduce un nombre:" read -s nombre

Case

case $opcion in 0) ${ECHO} -e "[CORRECTO];" ;; *) ${ECHO} -e "[INCORRECTO];" ;; esac

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Diff

Ejemplo visualización en columnas

diff -y fichero1.txt fichero2.txt

Ejemplo comparar sin diferenciar espacios en blanco ni tabuladores

diff -wEZB fichero1.txt fichero2.txt

Ejemplo modo silencioso

Importa el resultado del commando diff result=0 EXIT OK, result=1 FAIL.

result=$(diff -q --ignore-matching-lines="ntp clock-period" fichero1.txt fichero2.txt)

Ejemplo ignorando lineas

Las líneas con contenido "ntp clock-period" son ignoradas.

diff --ignore-matching-lines="ntp clock-period" fichero1.txt fichero2.txt

Comandos utilies del diff

diff --suppress-blank-empty suppress space or tab before empty output lines
-y, --side-by-side output in two columns -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -q, --brief report only when files differ --suppress-common-lines do not output common lines

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URLs Referencia:

• https://www.computerhope.com/unix/udiff.htm