A repository of information technology questions and answers

Latest posts

Setting up an SSHD failover daemon in Ubuntu

1 minute read    3596 visits.

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 Linux memory cache and swap

3 minute read    1320 visits.

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

Clearing GPG BADSIG errors during update

1 minute read    2792 visits.

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

What are access control lists (ACLs)?

2 minute read    450 visits.

Access control lists (ACLs) allow you to assign permissions to many different users and groups on individual files or directories.

Mounting DFS on Oracle Linux

1 minute read    4090 visits.

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

NetWorker 9.0 Server supported platforms

1 minute read    3270 visits.

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.

Tomcat 7 on CentOS 7

1 minute read    3161 visits.

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

Moving from LAMP to LEMP

3 minute read    3208 visits.

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

RPM cheat sheet

1 minute read    3456 visits.

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

Installing PHP GeoIP on Ubuntu

1 minute read    3125 visits.

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

LVM Logical Volumes

3 minute read    3643 visits.

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

2 minute read    3011 visits.

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

3 minute read    3032 visits.

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

Private and public key pairs for SSH

3 minute read    2238 visits.

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

2 minute read    3065 visits.

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

SSH related commands

1 minute read    1877 visits.

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

Using AIDE to ensure Linux server integrity

4 minute read    3110 visits.

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.

Recovering from a lost root password under Linux

1 minute read    3307 visits.

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.

Changing UIDs and GIDs for a user

1 minute read    3381 visits.

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

Creating a local yum repository for Puppet

2 minute read    3088 visits.

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

Changing Oracle Enterprise Linux hostname

1 minute read    2749 visits.

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

Red Hat 6 (RHEL) run levels

2 minute read    3044 visits.

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

1 minute read    2797 visits.

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

1 minute read    3073 visits.

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.

Find command examples

3 minute read    2285 visits.

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

Using the apt-get command cheat sheet

1 minute read    2898 visits.

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.

Multipathing with mdadm on Linux

2 minute read    949 visits.

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

Extract a single file from ISO image

1 minute read    2913 visits.

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

List directory contents of an ISO image

1 minute read    3281 visits.

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

How much memory is in this UNIX system?

1 minute read    2938 visits.

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.

Equivalent UNIX and DOS commands

3 minute read    3613 visits.

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.