Category Archives: Operating System

Block Countries by IP on Debian Trixie with nftables and xtables-addons

Posted on May 11, 2026 by Ceecee Newman

Debian Trixie uses nftables as its default firewall. If you’re used to iptables, the commands still work — but they go through an iptables-nft compatibility shim that translates them to nftables rules under the hood. For country-based IP blocking, the … Continue reading →

Posted in Linux | Tagged debian, geoip, nftables, security | Leave a comment

List open or listening ports

Posted on March 29, 2019 by ronaldpringadi

You started a service, you can’t tell whether it actually bound to its port, and you want to see what’s listening — or you want to find out which process is squatting on port 8080. Two one-liners, two operating systems: … Continue reading →

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CentOS 6 repo Settings

Posted on March 2, 2018 by ronaldpringadi

To fix repo settings in CentOS 6 1. make sure there is no proxy or funny settings in vi /etc/yum.conf 2. There are a couple of files within /etc/yum.repos.d/. Make sure the url are correct (accessible) and enabled=1 ll /etc/yum.repos.d/ … Continue reading →

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Show Linux Partition Tree Mountpoint and If SSD

Posted on June 27, 2017 by ronaldpringadi

1lsblk -o TYPE,NAME,KNAME,UUID,MOUNTPOINT,SIZE,ROTA

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SELinux directory permission

Posted on November 8, 2016 by ronaldpringadi

To check SELinux directory permission you need to -z for example 1ls -Z /var/www/html If something is incorrect you can re-adjust some of the directory permission: 1chcon -R -t httpd_sys_content_t /var/www/html

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RedHat / Centos Firewall

Posted on November 8, 2016 by ronaldpringadi

To add an exception to firewall In RedHat/CentOS 6 12345iptables –line -vnL iptables -A INPUT -p tcp –dport 80 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p tcp -s 192.168.0.0/16 -j ACCEPT iptables -D INPUT -p tcp -s … Continue reading →

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Bash string comparison

Posted on September 6, 2016 by ronaldpringadi

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465#!/bin/bash function test(){ echo "" echo "TEST $1" echo "VAR_1: $VAR_1 VAR_2: $VAR_2 " if [ "$VAR_1" = "false" ]; then echo " VAR_1 is false"; fi if [ "$VAR_2" = "false" ]; then echo " VAR_2 is false"; fi … Continue reading →

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