Wednesday, July 6, 2016

NMap, SSH and Matrix the Movie

Matrix the movie is one of the coolest movie with concepts that provoke thoughts of technology and politics.

Ever thought that open source was involved? Surprise, surprise, trinity was referring to the use of Nmap and SSH exploits.


Monday, June 20, 2016

Backup Thunderbird 45 on MS Windows 10

Just after installing the Kubuntu Jaunty 9.04 Linux, its time to restore some of my stuff. Firstly, I need communications and this is via my Thunderbird.

Thunderbird email client allow access of emails from online email providers and a local storage of email. It may be necessary to move these local emails and local Thunderbird profile to another PC or to be saved as a backup.

Here is the manual method. Save the local configurations by copying the files as listed in these locations to the backup location.

  • Thunderbird 45.1.1
  • MS Windows 10


Step 1. Identify location of the files for backup.

There are a few ways to do this, one of which is to open Thunderbird menu (3 horizontal lines), click Options-> Account settings. Then follow the steps below.
1. Signature. Right click the email account-> Account settings. In the right window, look for
Attach signature from a file instead

2. Email configuration profile. Right click the email account-> Account setting ->Server Settings ->Local directory

3. Local folders for offline access. Right click the Local folders ->Server Settings ->Local directory

4. Digital certificates. Right click the email account-> Account setting ->Manage Identities...
Then choose the email profile(s) and click Edit and choose the tab for Security.

Step 2. Stop Thunderbird and compact all large folders.


Empty all Deleted folders

Step 3. Copy files in Step 1 to the new location.


Step 1:
Copy the directory profile back to the new system

Step 2:
In the terminal create an email profile that uses the old directory, type

thunderbird -profilemanager


Friday, May 20, 2016

Howto convert photos to line drawing with GIMP

GIMP provides a large tool set to edit photos. This software is provided with GNU License and is available to use on Linux and MS Windows computers.

Artistic look from photos can be created with a few steps in GIMP 2.8.8.

Start GIMP and open the photo (which is in colour).

Step 1: Select the photo.
From the main menubar, click Select ->All or press "Ctrl+A"

Moving dots/dashes should be around the photo.

Step 2: Remove colour from the photo.

Click the menu Colors ->Desaturate... and choose a shade of gray based on Lightness or Luminosity or Average. Click "OK"

Alternative method:
Click the menu Colors ->Hue-Saturation... and slide Saturation value all the way to left or -100.

Step 3: Strip gray tones

Click the menu Filters ->Edge-Detect ->Difference of Gaussians...
Default checks the boxes Normalize and Invert. Radius 1 value is 3.0 and Radius 2 is 1.0.

Note: At this point if it results in a blank image, remove the Alpha channel

Step 4: Raise the lines

Click the menu Colors ->Brightness-Contrast...

Increase brightness value and reduce contrast value until image appears. Click "OK"

Step 5: Enhance the light lines

Click the menu Colors ->Levels... and click "Auto".
In the graph like "Input Levels", slide the triangle till to left until the desired tone. Click "OK"


Thursday, March 17, 2016

Centos 6 Checklist on Systems Security

Linux Security Checklist

A reliable server is only as good as it is maintained and due processes applied. A systems security checklist template for Centos 6 mentioned below serves to meet the basic security requirements. A more stringent and targeted checklist can be developed further.

This mainly records existing system details and follow common practices. Some stuff like SELinux is mentioned as permissive as this is what I have at the moment. Details should be updated to specific server needs. Another useful checklist is for web application deployment and can be found at

Centos 6 Checklist on Systems Security (link)

Contents of the checklist includes;

Section A. Details of the system
Section B. Services
Section C. Essential files
Section D. Examples.

Monday, March 14, 2016

NFS Commands 101

Refer to previous article Setup File Sharing with NFS on Centos Linux.

I find NFS version 3 is the most commonly used and uses remote procedure call (RPC) to manage connection between client and server. The service called rpcbind in Centos 6 has replaced portmap to handle RPC (see nfs4). Version 3 onward support files larger than 2 Gb size.

Whenever an NFS server is restarted not gracefully, the service rpc.statd notifies NFS clients. When quota is applied to the NFS, the service rpc.rquotad handles quota information.

The file /etc/exports define which directories are available to NFS clients. Each share is placed on a separate line and it indicates which client can access along with the options. Default users access a share as the user nobody, where this can be overridden in the /etc/exports option.

E.g. The following /etc/exports shares the directory /data with the client The client may read and write and mounts synchronously.


Or user connect as its own user


Default ports used by NFS are 2049 for the NFS service and 111 for RPC service.

Here are a list of NFS version 3 commands. Most are at the client side unless specified.

General NFS Commands

Start and stop NFS service
# service nfs start
# /etc/init.d/nfs start
# service nfs stop

Enable NFS service at boot
#chkconfig nfs on

Refresh NFS server shares from /etc/exports
# exportfs -r

Unload and reload NFS shares from /etc/exports
# export -a

Check support for NFS on the kernel. Did you forget to compile kernel with NFS support?
# lsmod |grep nfs
# grep -i nfs /boot/config

Check if list of commands are running
# rpcinfo -p

Display NFS statistics as client
# nfsstat -c

Display use of io
# vmstat -s

Mounting NFS

Display available NFS mounts
# showmount -e servername

Mount an NFS share
# mount -t nfs servername:/the/sharename

Display if the NFS mount is full or its free space
# df -k

Troubleshoot reference

Howto check Linux memory usage

Ever found a Linux suddenly having low free memory or none at all? This is something to check when the server suddenly starts slowing down or not able to complete processes.

Here are several method to diagnose and maybe identify a fix. Check the memory usage then identify the process causing the extreme usage. Next, work on that process configuration.

Check memory usage

Display available and used memory with 'free' command
# free
# free  -m

The top live monitor
# top

Press m to display memory
Press Shift + m to sort by memory percentage
Press R to reverse the sort

List processes and amount of memory being used
# ps -e -o pid,vsz,comm=
# ps -e -o pid,vsz,comm= | sort -n -k 2

# ps aux  | awk '{print $6/1024 " MB\t\t" $11}'  | sort -n

View meminfo
# cat  /proc/meminfo
# vmstat -s

View the RAM device installed
# dmidecode -t 17

Check the process

List processes that open files
# lsof

Several TYPE of files are monitored

REG – Regular File
DIR – Directory
FIFO – First In First Out
CHR – Character special file

A description of the file is shown by FD
cwd – Current Working Directory
txt – Text file
mem – Memory mapped file
mmap – Memory mapped device
NUMBER – Represent the actual file descriptor. The character after the number i.e ‘1u’, represents the mode in which the file is opened. r for read, w for write, u for read and write.

List processes base on process names
# lsof -c ssh

List processes base on process id
# lsof -p 1234

Where 1234 is an example of the process id (pid).


Tuesday, March 8, 2016

Boot Centos Linux to Windows

Centos 6 and 7 provide different approach for booting to a graphical windows interface known as X. Firstly, ensure the relevant packages to support display of windows where most of it are bundled as one of the popular Linux desktop environments.

Among the popular current desktops environments available are;

  • Gnome
  • KDE
  • Unity
  • Xfce
  • LXDe
  • Cinnamon
Here are the steps.

Centos 6 Approach

Edit the file /etc/inittab and change the number 3 to 5 as shown in the line below


Then reboot.

To start graphical windows without reboot, at the command prompt type

init 5

Centos 7 Approach

Login as root and the prompt type

sudo systemctl set-default

Then reboot.

To start graphical windows without reboot, at the command prompt type

sudo systemctl start


Install GIMP on Centos 6

Centos 6.6 provides the popular graphic editing software GIMP at version 2.6.9. The current stable release is GIMP 2.8 for those who seek the additional editing features (link). Existing Centos 6.6 does not have the required newer libraries to support GIMP 2.8.

The details of GIMP is described as below.

Name        : gimp                         Relocations: (not relocatable)
Version     : 2.6.9                             Vendor: CentOS
Release     : 8.el6_6                       Build Date: Thu 20 Nov 2014 02:06:25 PM EST
Install Date: Tue 08 Mar 2016 03:09:46 PM EST      Build Host:
Group       : Applications/Multimedia       Source RPM: gimp-2.6.9-8.el6_6.src.rpm
Size        : 48118103                         License: GPLv2+
Signature   : RSA/SHA1, Thu 20 Nov 2014 04:10:42 PM EST, Key ID 0946fca2c105b9de
Packager    : CentOS BuildSystem
URL         :
Summary     : GNU Image Manipulation Program
Description :
GIMP (GNU Image Manipulation Program) is a powerful image composition and
editing program, which can be extremely useful for creating logos and other
graphics for webpages. GIMP has many of the tools and filters you would expect
to find in similar commercial offerings, and some interesting extras as well.
GIMP provides a large image manipulation toolbox, including channel operations
and layers, effects, sub-pixel imaging and anti-aliasing, and conversions, all
with multi-level undo.

Flexibility on editing include availability of many brushes and patterns.

 Here are steps to install the standard GIMP version 2.6.9

Step 1: Install GIMP

# yum install gimp

Step 2: Install additional brushes and patterns

Install additional brushes and patterns. Brushes include swirls and text to enhance strokes. Patterns such as clouds and funnymess.

yum install gimp-data-extras

Start GIMP from the desktop menu. Click Applications ->Graphics ->GNU Image Manipulation Program


Saturday, February 20, 2016

Install OSMC on Raspberry Pi2

Raspberry Pi 2 (RPI2) provides a flexible multimedia centre for movie streaming, watching youtube, using a web browser and options to addon many Linux applications. OSMC is one of the images that can be downloaded unto an RPI2 from (download page or FTP). This Debian Jessie based system is great at running the RPI2 and allow developers space to enhance to their needs.

The media player system KODI, provides an interface to multimedia contents such as movies, online TV, videos, photos and musics. KODI itself does not have any media contents, but due to its extensible nature, many developers have created plugins to access external contents and addons to extend its functionalities. Media contents could reside in the same device as KODI, in a local area network, stream from the internet or cached contents from internet. KODI 15 comes with the current OSMC.

* Consider OSMC as an upgrade of Raspbmc.

This is an update to previous post "Raspberry Pi: Getting Started with OSMC" and I do not expect it to go into too much details. When I mention OSMC, it might also refer to KODI as its typically the only screen seen when running this RPI2.

Step 1: Starting OSMC

Download OSMC image from and image copy the .img file to the blank SD card. Tools such as Win32 Disk Imager can be used for this purpose.

Plug SD card into RPI2 and start RPI2 (already have internet connection).

Automatically start installation process.

It will reboot once installed successfully.

Step 2: Basic configuration

The default layout uses OSMC skin. Below is the OSMC main menu screen. Default appearance is handled by the skin called OSMC.

 It shows the following options;
  1. Videos
  2. Music
  3. Pictures
  4. My OSMC
  5. Favourites
  6. Programs
  7. Settings
  8. Power

Configure Screen size

The screen display may appear outside of the screen area. Change the zoom size until everything meets your satisfaction. From OSMC home page, click Settings ->Appearance ->Skin. Choose your zoom level and press Esc key until back to OSMC main menu.

Configure Timezone

Configure the timezone for correct time display. Click Settings ->Appearance ->International. Choose your region and the OSMC time should be update instantly.

Configure Skin

Default skin OSMC can be changed to KODI's default skin called Confluence. From OSMC home page, click Settings ->Appearance ->Skin. Choose skin as confluence and press Esc key until back to OSMC main menu.

More notes from KODI website: Quick start guide, Home screen controls,

Step 3: Add Youtube addon

In Videos menu there is an option to link your Youtube account with OSMC. This allows viewing of all your Youtube channels. From the OSMC main menu, click Videos ->Video add-ons ->Get more... ->Youtube

Click Install

Click launch. (From the OSMC main menu, you can click Videos ->Video add-ons to watch Youtube).

Follow the instructions on screen.
One of this includes accessing on a PC to enter the code given by the add-on in OSMC.


1. Mode Not Supported

If after installation process, RPI2 boots and screen displays a message "Mode Not Supported", it means the display resolution was not automatically detected correctly. This happens on one Samsung TV.

SSH into the OSMC and edit  /boot/config.txt
See command line tips at Raspbian Command Line Basics 101

Updated file for mode CEA

ALTERNATIVE Updated file for mode DMT

2. Youtube add-on errors/issue.

Successfully login after the 2 google app authorisation, but displays empty list and
Display error exceeded quota (of some sort)

Step 1: Activate the Google API v3
All Google App requires API v3, as derived from forum posting #2904.

Login to your google developer account and enable the above API.

Step 2: Use your own browser key, Oauth id and secret.
Looks like the default developers combination of above does not allow too many to use it. In posting #2847.

Login to your google developer account and create the above. A new project is created if none is created yet.

The newly created info from above should be updated in the file that is found in /home/osmc/.kodi/addons/​/youtube/client/

Find the line as below and edit the key, id and secret values.

'youtube-for-kodi-15': {
            'system': 'Isengard',
            'key': 'The_browser_key',
            'id': '',
            'secret': 'The_oauth_secret_word'