A repository of information technology questions and answers

Latest posts

Multipathing with mdadm on Linux

mdadm multipathing is a failover solution (no load balancing) what means that only one path is used at any one time.

Clearing Linux memory cache and swap

Every Linux system has three options when clearing cache without interrupting any processes or application services.

SSH related commands

A short article which provides a brief description for ssh related commands

RPM cheat sheet

RPM is a command line package management utility used for installing, uninstalling, updating, querying and verifying software packages.

Private and public key pairs for SSH

SSH has a key management capacity and related agents.When configured with public key authentication, your key proves your identity to remote SSH hosts

SSH configuration and security best practices

Here is a list of processes and configurations that you can use to tighten and enhance SSH security with regard to remote host access

Oracle Linux and Solaris command comparison

This document explains how to use Oracle Solaris to users who have experience operating systems in a Linux environment.

Find command examples

The find command in UNIX and Linux is a command line utility allowing you to search for files in a directory hierarchy.

List directory contents of an ISO image

isodump is a crude utility to interactively display the contents of iso9660 images in order to verify directory integrity

Extract a single file from ISO image

isodump is a crude utility to interactively display the contents of iso9660 images in order to verify directory integrity

How to Change or Set hostname on OEL/RHEL/CentOS 7

Unlike OEL/RHEL/CentOS 6, manually appending “HOSTNAME=xxxxx” into file /etc/sysconfig/network and restarting system will not work on version 7.

How to Change or Set hostname on OEL/RHEL/CentOS 6

A simple post for those who are new to Oracle Enterprise Linux (OEL) or Red Hat Linux (RHEL) version 6 and wish to change hostname.

LVM Logical Volumes

The use of logical volumes is similar to the use of partitions and is accomplished with the same standard commands (mkfs, mount, fsck, df, ...)

LVM Volume Groups

A volume group (vg) is an abstraction layer between block devices and logical volumes. The commands used to manage a volume group start with vg

LVM Physical Volumes

A physical volume (pv) is any block device (a disk, a partition, a RAID device, an iSCSI device, etc.)

Changing UIDs and GIDs for a user

A quick procedure to change the UID and GID for a given user using the usermod and groupmod commands.

Installing PHP GeoIP on Ubuntu

A simple article providing the steps necessary to get GeoIP working with PHP on Ubuntu systems.

How to disable Unity overlay scrollbars in Ubuntu

How to easily restore the classing scroll bar (disable overlay scrolling) or to re-enable it if disabled under Ubuntu 14.04 and 16.04 LTS

Setting up an SSHD failover daemon in Ubuntu

A simple article on how to create a failover SSH server on a Ubuntu system, allowing you to connect on an alternative port of the original SSHD fails

Clearing GPG BADSIG errors during update

During a test build of Ubuntu 15.10 I suddenly received the following error when refreshing the packages from the repository.

Mounting an Mac OS X install DVD in Ubuntu 14.04

This document describes how to use a Linux computer to extract the BaseSystem.dmg image file from an Mac OS X (10.7+) installation DVD

Using AIDE to ensure Linux server integrity

AIDE provides an additional layer to your server security not by keeping intruders out but by notifying you as the sysadmin of a possible intrusion.

Uninstalling VMware Workstation from a Linux Host

This article provides the simple steps needed to uninstall the VMware workstation from a Linux host. You must run the command from a Linux server.

NetWorker 9.0 Server supported platforms

With the release of 9.0, the NetWorker Server and Management Console will now run only on Linux 64-bit and Windows 64-bit systems.

Recovering from a lost root password under Linux

This article provides a quick procedure on how to recover a lost root password frm virtually any version of Linux which uses the GRUB boot loader.

Configuring a basic firewall under Ubuntu 14.04

This article provides a quick reference to UFW commands that will create iptables firewall rules are useful in common, everyday scenarios.

Creating a local yum repository for Puppet

Puppets automated management of installed applications and libraries can be enhanced with custom package repositories such as a custom repository.

Tomcat 7 on CentOS 7

This post provides a basic installation and configuration of Tomcat 7 on a CentOS 7 server.

Moving from LAMP to LEMP

LAMP is a popular server stack using apache to deliver dynamic content; LEMP utilises ngnix to achieve the same open source technologies.

Using the apt-get command cheat sheet

APT originally designed as a front-end for dpkg to work with debian packages, but it has since been modified to also work with the RPM via apt-rpm.

Equivalent UNIX and DOS commands

There are commands that do the same things in Windows DOS and from the command prompt as in UNIX, they just have a different syntax.

How to configure Single-Sign-On using OpenSSH on HP/UX

How to configure SSH to allow access using GSSAPI and achieve single-sign-on using vendor supplied OpenSSH or OpenSSH downloaded from the internet.

Changing Oracle Enterprise Linux hostname

Either due to cloning or corporate naming standards, you may find the need to change the hostname of an Oracle Enterprise Linux System.

Disabling Spotlight under Mac OS X (updated)

If like me you're not a fan of Spotlight and want to disable it completely then you can hese simple steps.

Red Hat 6 (RHEL) run levels

The idea behind SysV init runlevels revolves around the idea that different systems can be used in different ways.

Switching to a GUI login on RHEL 6

To switch to a graphical environment, you may need to install additional software from the RHEL Internet repository or installation DVD.

Disabling SELinux in Oracle Linux 6

In this post, we walk through steps you can follow to check the status of SELinux and also disable it in OEL 6, if it is enabled.

Mounting DFS on Oracle Linux

A short article on how to mount a DFS (distributed file system) on an Oracle Linux 5.11 system.

Configure iSCSI with Multipathing on RHEL 6

A simple post which outlines the steps needed to configure iSCSI with Multipathing on Red Hat Enterprise Linux 6.5

How much memory is in this UNIX system?

This is a relatively simple question, but alas, poor Yorick!, the answer is not plain sailing as all flavors of UNIX and Linux have different tools.