Filed under Linux/Unix

How To Remove Old Kernels In CentOS

Ever had the the “no space left” message after trying to install a new kernel ? The thing is that by default the system will keep the old kernels there, so the best option is to set it to delete the old ones automatically. Starting from the beginning: For one self information, check how many … Continue reading

How to start shell script writing

This is actually, I want to share, how I learned the shell scripting. It may be helpful for beginners. I am writing it step by step so that it will easy to understand: STEP 1: Do your task manually & prepare the steps. If you know the basic Linux commands, it will help you to … Continue reading

Commands You Should Never Run on Linux

Linux’s terminal commands are powerful, and Linux won’t ask you for confirmation if you run a command that won’t break your system. It’s not uncommon to see trolls online recommending new Linux users run these commands as a joke. Learning the commands you shouldn’t run can help protect you from trolls while increasing your understanding … Continue reading

Using DMVPN with Linux

DMVPN is a very intelligent combination of IPsec, GRE and NHRP. Many Thanks to the Guys at Cisco, Christoph, Frederick and all other. This week i discovered “opennhrp” on sourceforge. It took me a minute or two to have a VM with debian up and the needed tools installed. I used VMWare with a bridged … Continue reading

SYSLOG Server en Linux [SP]

Niveles de Log de menos severo a más severo. 7 (info) a 0 Si se especifica un nivel incluye los inferiores. el tres incluye 2,1 y 0 El nivel 3 es alerta y el 2 es critico. Servidor Syslog en Linux. – Editar /etc/default/syslogd syslogd=”-r” – Relanzar syslog /etc/init.d/sysklogd – Ver las constantemente las últimas … Continue reading


OpenNHRP implements NBMA Next Hop Resolution Protocol (as defined in RFC 2332). It makes it possible to create dynamic multipoint VPN Linux router using NHRP, GRE and IPsec. It aims to be Cisco DMVPN compatible. Download

Time to live (TTL)

Time to live (TTL) is a mechanism that limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded. In computer networking, TTL prevents a data … Continue reading

Configuring Virtual Hosts in Apache

The configuration detailed here represents the Apache virtual host configuration which gives the web server administrator the greatest flexibility and freedom for specifying virtual hosts based on both name and port number. Obviously not all configuration directive have been included; I didn’t want to confuse the issue by including a full httpd.conf/httpsd.conf file — only … Continue reading

Basic LINUX commands

Basic Navigation File Manipulation More File Manipulation Account Maintenance File Archival Basic Navigation ls directory listing ls Basic listing ls -F Basic listing, with file type notations (-F) ls -al Listing, showing all, including hidden, files (-a) in long format (-l), which includes permissions, modify dates, ownership, etc cd change directory cd or cd ~ Change to … Continue reading

L2TP VPN using xl2tpd

L2TP (Layer 2 Tunneling Protocol) is a tunneling protocol used for VPNs. It uses the UDP port 1701 to communicate. It doesn’t have any encryption, but we can encrypt the L2TP packets by using it with IPSec. For theoretical information on L2TP you can visit its Wiki. In Linux, you can find so many different applications … Continue reading

How to fix “HostDatastoreSystem.CreateNasDatastore” for object “ha-datastoresystem” error when setting up VMware ESXi NFS data store

If you try to add a remote NFS data store forVMware Esxi, you may encounter this error: Call “HostDatastoreSystem.CreateNasDatastore” for object “ha-datastoresystem” on ESX “{ESX server}” failed: This is often a firewall issue, and the very first place you should look. Browse to Configuration/Software/Security Profile and verify that the  “NFS Client” is listed under “Outgoing … Continue reading