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Ansible

Ansible is an open source, powerful automation software for configuring, managing and deploying software applications on the nodes without any downtime just by using SSH. Unlike other alternatives, Ansible is installed on a single host, which can even be your local machine, and uses SSH to communicate with each remote host. This allows it to […]

MySQL and PostgreSQL rosetta stone

This is a short table of useful and common MySQL & PostgreSQL commands put up against each other.

MySQL PostgreSQL Command line client mysql psql Connect to database use mysql; \connect postgresql; List databases show databases; \l List tables show tables; \dt Describe table describe table; \d table; Show server version select version(); select version(); […]

Disable IPv6 lookups with Bind on RHEL or CentOS

Discovered during a recent project. Bind / Named was constantly spamming the logs about it being unable to reach root servers. The logs revealed that we were talking IPv6 addresses. Which was assumed to be disabled.

The less cool part was that in “/etc/named.conf” the following was commented out.

// listen-on-v6 port 53 { ::1; […]

Setting up sSMTP with GMail

Let me introduce you to the “extremely simple MTA to get mail off the system to a mailhub”. Particularly useful when you don’t want systems to have a full blown MTA installed. Such as Postfix, Exim or Sendmail. I find ssmtp extremely helpful on standalone servers that use Logwatch.

Getting this up and running requires […]

Changing the default PostgreSQL data folder (PGDATA)

Installing the PostgreSQL server on RHEL, CentOS, Scientific Linux or Fedora installs the PostgreSQL databases and configuration files in “/var/lib/pgsql/data”.

This may or may not be desirable. Let’s assume for a moment you have a separately crafted partition for PostgreSQL to use, let’s say a RAID10 volume. You’d want to change this.

Change the defaults […]

Resetting the root/postgres password for PostgreSQL

The following is required to reset the root/postgres user password for PostgreSQL. The distribution used in my example is CentOS 5.5 and PostgreSQL 8.4.

Note: By default there’s no password for the postgres user.

In step 2 and 5 you will most likely not be using “ident” but rather “password” or “md5?.

1. Shut down […]

Kick start install CentOS 6.5 Install Problem Unable to read group information from repositories.

 CentOS 6.5 Install Problem// // //

CentOS 6.5 Install Problem I have recently installed CentOS 6.5 on a couple of computers, once without any problems and once with a fatal hang during install.  With both installs I chose to overwrite any existing partitions and use the whole hard-drive.The problem during the failed install happened […]

LINUX COMPLETE GUIDE WITH SHELL TIPS

SYSTEM

Hardware | Statistics | Users | Limits | Runlevels | root password | Compile kernel | Repair grub | Misc

Running kernel and system information # uname -a # Get the kernel version (and BSD version) # lsb_release -a # Full release info of any LSB distribution # cat /etc/SuSE-release # Get SuSE version […]

Ansible centos 6

Ansible is a configuration management tool, deployment tool, and ad-hoc task execution tool all in one.

It requires no daemons or any other software to start managing remote machines — it works using SSHd (using paramiko, to make it smoother), which is something nearly everyone is running already. Because it’s using SSH, it should easily […]

Zombie Process

Zombies don’t just appear in scary movies anymore, sometimes they also appear on your Linux systems; but don’t fret they are mostly harmless.

What is a Zombie Process?

Before we get started I wanted to first cover what exactly a Zombie process is.

Linux and Unix both have the ability for a process to create […]

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