How to Check If an Application is Installed in Ubuntu

 Linux  Comments Off on How to Check If an Application is Installed in Ubuntu
Dec 012016

In this brief post, I’ll quickly show you how to check via the terminal if a particular program is installed on an Ubuntu Linux system.

For easy understanding, I will consider a program that is already installed (keepassx) on my computer and one that is not installed nmap.

On the terminal, there are two reliable ways to find out if a program is installed on an Ubuntu or Linux Mint system: Via apt-cache policy or by running dpkg. Continue reading »

 Posted by at 10:20 am

Differences between yum info and yumdb info with Example

 Command Line, Linux  Comments Off on Differences between yum info and yumdb info with Example
Apr 262016

Wise folks say a picture is worth a thousand words.

In Linux, an example is worth ten thousand words.

In this post, we’ll use an example to understand the difference between the commands yum info and yumdb info.

For purpose of this post, I will use the popular Cherrytree notes application.

In both examples I’ve run the commands after installing cherrytree.

By the way, I’m running the below commands on a CentOS 7 system.

So here we go, first with the yum info command.

yum info

[tommy@localhost ~]$ yum info cherrytree
Loaded plugins: aliases, changelog, fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
Installed Packages
Name        : cherrytree
Arch        : noarch
Version     : 0.36.9
Release     : 1.el7
Size        : 3.1 M
Repo        : installed
From repo   : epel
Summary     : Hierarchical note taking application
URL         :
License     : GPLv3+
Description : CherryTree is a hierarchical note taking application, featuring rich text and
            : syntax highlighting, storing all the data (including images) in a single XML
            : file with extension ".ctd".

Now let’s consider yumdb info with the same cherrytree application.

yumdb info

[tommy@localhost ~]$ yumdb info cherrytree
Loaded plugins: fastestmirror, langpacks
checksum_data = febc31650e96f822cb1a4e52c66aa4a9e71503f861680b3fa3385a478300b7ed
checksum_type = sha256
command_line = install cherrytree
from_repo = epel
from_repo_revision = 1461632780
from_repo_timestamp = 1461640240
installed_by = 1000
origin_url =
reason = user
releasever = 7
var_infra = stock
var_uuid = 72c6b420-9095-4304-90a7-fbb60a47ec6a
[tommy@localhost ~]$ 

yumdb info provides information like the checksum data and type, command used to install it, the repository and the person (userid) who installed it but nothing about the application or the developer.

However yum info provides information about the application (both in summary form and in a slightly longer version) as well as the file size. But yum info provides no information about the checksum data or type, the command used for installation or the person (userid) who installed it.

So which command you want to use will depend on your unique needs.

 Posted by at 12:34 pm

How To Add Guest Additions to Lubuntu 16.04

 How To, Linux  Comments Off on How To Add Guest Additions to Lubuntu 16.04
Apr 262016

I have Lubuntu running as a virtual machine via VirtualBox.

Like many Ubuntu fans, I upgraded to version 16.04 LTS (Xenial Xerus) yesterday.

The reason for my upgrade was that Ubuntu 15.10 (a.k.a. Wily Werewolf) was not a Long-term Supported distribution.

Support for Ubuntu 15.10 ends in July 2016 while Ubuntu 16.04 LTS will be supported until April 2021.

The upgrade from Ubuntu 15.10 to Ubuntu 16.04 LTS went smoothly.

Following the upgrade, I rebooted my virtual machine.

And then came the familiar problem all of us confront with VirtualBox – screen resolution issue.

The problem is that the monitor settings (screen resolution) will be off and the desktop will not occupy the full screen.

Irritating but not a showstopper.

However, the problem can be fixed quickly.

This is how I fixed the screen resolution issue after upgrading from Ubuntu 15.10 to Ubuntu 16.04 LTS.

I opened up the terminal and installed virtualbox-guest-dkms.

tommy@johnson:~$ sudo apt-get install virtualbox-guest-dkms
[sudo] password for tommy: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libnotify-bin virtualbox-guest-utils virtualbox-guest-x11
The following NEW packages will be installed:
  libnotify-bin virtualbox-guest-dkms virtualbox-guest-utils virtualbox-guest-x11
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,986 kB of archives.
After this operation, 13.1 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 xenial/main amd64 libnotify-bin amd64 0.7.6-2svn1 [6,584 B]
Get:2 xenial/multiverse amd64 virtualbox-guest-utils amd64 5.0.18-dfsg-2build1 [387 kB]
Get:3 xenial/multiverse amd64 virtualbox-guest-dkms all 5.0.18-dfsg-2build1 [551 kB]
Get:4 xenial/multiverse amd64 virtualbox-guest-x11 amd64 5.0.18-dfsg-2build1 [1,041 kB]
Fetched 1,986 kB in 0s (2,399 kB/s)         

Once the installation is complete, there’s one more step.

You need to reboot the newly upgraded virtual machine (Ubuntu 16.04 LTS).

$ sudo reboot

After rebooting,you should now have access to the full screen.

As simple as that.

Related Posts:
What are Guest Additions?
 Posted by at 10:04 am

How to Change Default Kernel in CentOS 7

 Command Line, Linux  Comments Off on How to Change Default Kernel in CentOS 7
Mar 282016

A typical CentOS 7 Linux system has multiple kernels.

How many kernels you have in your CentOS systems depends on the configuration setting.

Sometimes you might feel the need to change the default kernel to a different one (it may be an older or newer kernel) to ensure a particular application runs well.

Here’s how to change the default kernel at boot time.

List Available Kernels

First, let’s list the available kernels on our CentOS 7 system with the following command (you need to be root).

$ sudo egrep ^menuentry /etc/grub2.cfg | cut -f 2 -d \'
CentOS Linux (3.10.0-327.10.1.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-327.4.4.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-327.3.1.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-229.20.1.el7.x86_64) 7 (Core)
CentOS Linux, with Linux 0-rescue-ddf73bd8a3a44950a327a6961955c015

Once you have the kernel list, you can decide which kernel you want as the default boot kernel.

Change Default Kernel

Multiple kernel boot options are available to us in the above list.

Now it’s time to set our preferred boot kernel.

Important – The boot options in the above kernel list start at 0.

So if you want the 3.10.0-229.20.1.el7.x86_64 kernel as the default kernel, note that its boot option will be 4 in the above list.

Now let’s set 3.10.0-229.20.1.el7.x86_64 as our default kernel with the sudo grub2-set-default command.

$ sudo grub2-set-default 4

After changing the default kernel, you must reboot (remember to close all your open applications).

$ sudo reboot

Once the system has come up after reboot, it’s time to check if the default kernel has changed via the uname -r command.

$ uname -r 

Voila, changing the default boot kernel in CentOS 7 is as simple as that.

Related Posts
Get Rid of Old Kernels in CentOS 7 and Red Hat 7
 Posted by at 11:50 am  Tagged with:

Linux Mint 18 to be Supported Until 2021

 Linux  Comments Off on Linux Mint 18 to be Supported Until 2021
Jan 072016

The upcoming Linux Mint 18.x series a.k.a. Sarah will be based on Ubuntu 16.04 LTS and supported until 2021.

The first version of Linux Mint 18 should appear toward the end of the first half of 2016, say in May or June.

Linux Mint developers have offered little details on Sarah except to say that it will “feature a new look and feel.”

For the etymologically inclined, Sarah is a popular Jewish feminine name common in North America, Europe and the Middle East.

Students of religion and history know Sarah as the wife of Abraham in the Hebrew Bible, Christian Old Testament and Quran.

Sarah is said to mean a woman of high rank in Arabic, Hebrew and Persian and is often translated as “Princess.”

Huge Success

One of the big desktop Linux success stories in recent years, Linux Mint has left rivals including its progenitor Ubuntu in the shade.

An extremely user-friendly distribution with a neat GUI, Linux Mint makes for a smooth transition for those coming from the wastelands of Windows.

The current version of this popular distro is Linux Mint 17.3 a.k.a. Rosa.

Based on Ubuntu 14.04 LTS, the Linux Mint 17.x series will be supported until 2019.

Separately, Linux Mint put out an update January 6, 2016 to facilitate an upgrade path from Linux Mint 17, 17.1 and 17.2 to Linux Mint 17.3 for all editions (Cinnamon, MATE, KDE and Xfce).

Instructions for the upgrade is available on the How to Upgrade to Linux Mint 17.3 section of the distro’s web site.

 Posted by at 4:37 pm

Linux Mint 17.3 XFCE, KDE Editions Delayed

 Linux  Comments Off on Linux Mint 17.3 XFCE, KDE Editions Delayed
Dec 142015

The Linux Mint development team has pushed back the release date of XFCE and KDE desktop versions of Linux Mint 17.3 a.k.a. Rosa to January 2016.

Launch dates for KDE and XFCE versions of Rosa were originally set for December 2015.

But with even the beta (trial version) of XFCE and KDE yet to see the light of the day and the holidays approaching there’s no way for the final release to happen in December.

The earliest that XFCE and KDE versions for Linux Mint 17.3 will debut is January 2016 or maybe a little later.

Linux Mint Project Leader Clement Lefebvre said the beta of KDE and XFCE versions of Linux Mint 17.3 could still be out in December.

The delay is not really such a big deal since the majority of Linux Mint users prefer the Cinnamon desktop environment that’s tailored for Linux Mint.

Cinnamon and Mate desktop versions of Linux Mint 17.3 are already available.

An advantage with the XFCE desktop is that it’s relatively lightweight compared to desktop environments like Cinnamon, Unity, Gnome 3 or KDE.

KDE is a more resource heavy desktop environment but is also more customizable.

 Posted by at 12:46 pm