TCP echo server using ncat

 ncat  -v -l -c 'while true; do read i && echo [echo] $i; done'  10.50.2.104 3000

UDP Client and Echo Server using netcat. for IPv6.

Client

nc -zuv6 2001:470:c2d7:917::38 3000

Server

nc -6lu 2001:470:c2d7:917::38 3000

Make Apache2 server HTTPS secure

1. Create key and cerificate files.

cd /etc/apache2/
mkdir -p ssl/crt
mkdir -p ssl/key 
cd ssl 
openssl req -newkey  rsa:2048 -nodes -keyout key/vhost2.key    -x509 -days 365 -out crt/vhost2.crt  

2. Configure Virtual host in the file /etc/apache2/sites-available/000-default.conf

...
<VirtualHost *.443>        

        DocumentRoot /var/www/secure

        ServerName vhost1.yourdomain.com

        # DirectoryIndex index.php

        ErrorLog /var/log/apache2/vhost1-error.log

        CustomLog /var/log/apache2/vhost1-access.log combined

        SSLEngine On

        SSLCertificateFile /etc/apache2/ssl/crt/vhost2.crt

        SSLCertificateKeyFile /etc/apache2/ssl/key/vhost2.key

        <Location />

        SSLRequireSSL On

        SSLVerifyClient optional

        SSLVerifyDepth 1

        SSLOptions +StdEnvVars +StrictRequire

        </Location>

        <Directory "/var/www/vhost1">

                Options Indexes FollowSymLinks MultiViews

                AllowOverride None

                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch

                Order allow,deny

                AddHandler cgi-script .py

                AddHandler default-handler .html .htm

                Allow from all

         </Directory>
</VirtualHost>

3. Install modes

    sudo a2enmod rewrite

    sudo a2enmod ssl 

3.  Restart Apache2 

    sudo service apache2 restart 

Installing new partition for swap space

1. Add new disk in VMWare. In the example it is 3rd disk.
    a. Power off machine
    b. Edit Settings
    c. Add ...   Hard Disk , Next
    d. Create a new virtual disk, Next
    e. Capacity 2GB , Thick provision Lazy Zeroed, Next , Next
    f. Finish
       
2. Create MS-DOS partition table.
    > fsdisk /dev/sdc
    > n (new)
    > p (primary)
    > 1 (first)
    > w (write) 

3. Install and used GUI program gparted
    > sudo apt-get install gparted 

4. Start gparted from Ubuntu GUI.  
   a. Select device GParted / Devices / dev/sdc1 
   b. Device / Create Partition Table , , Apply 
   c. Create partition: Patrition / New /
   d. Create as: Primary Patrition, File system: linux-swap, Label: swap / Add 
   e. Edit /  Apply All Operations 
   f. Partition / Swapon 
   g. GParted / Quit 

5. Make your changes permanent by adding entry to /etc/fstab file: 

mpug@testtool13:/$ vi /etc/fstab

# /etc/fstab: static file system information.
## Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices# that works even if disks are added and removed. See fstab(5).##
/dev/mapper/testtool97--vg-root /               ext4    errors=remount-ro 0       1
# /boot was on 
/dev/sda1 during installationUUID=b36b850c-0a22-4f02-9516-83b80d5a6c1f 
/boot           ext2    defaults        0       2
/dev/mapper/testtool97--vg-swap_1 none            swap    sw              0       0
/dev/sdc1                         none            swap    sw              0       0
/dev/fd0       /media/floppy0  auto    rw,user,noauto,exec,utf8 0       0
/dev/testtool97-disk/disk /disk               ext4    errors=remount-ro 0       1

Installation of package ExifRead

ExifRead is the package to read pictures attribute from files.

1. Download the file ExifRead-2.1.2.tar.gz 
2. >gunzip ExifRead-2.1.2.tar.gz
3. >tar -xvf ExifRead-2.1.2.tar 
4. >cd ExifRead-2.1.2
5. >sudo python setup.py install

Using MySQLdb with Python

To be able to connect python scripting  with MySqlDB install packages.
sudo apt-get install python-mysqldb
sudo apt-get install python-htmlgen 
sudo apt-get install phpmyadmin

use in python script 

import MySQLdb as mdb
import base64

SCRIPT = sys.argv[0].split("/")[-1:][0]
MYSQL_DATABASE_NAME='links'
MYSQL_USER='root'
MYSQL_PASSWORD=base64.b64decode('cm9vdDEyMw==')
MYSQL_PASSWORD='root123'
SQL_LIMIT = 500


database_name=MYSQL_DATABASE_NAME

con = mdb.connect('localhost',MYSQL_USER,MYSQL_PASSWORD,MYSQL_DATABASE_NAME)

cur = con.cursor()

Run Python as CGI in Apache2

1. Install apache2
sudo apt-get install apache2 

2. Install python
sudo apt-get install python 

3. Enable CGI processing in apache2
sudo a2enmod cgi

4. Modify file /etc/apache2/sites-available/000-default.conf to include:

        #ServerName www.example.com

        ServerAdmin webmaster@localhost
        DocumentRoot /var/www
        <Directory />
                Options FollowSymLinks
                AllowOverride None
        </Directory>
        <Directory /var/www/>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride None
                Order allow,deny
                allow from all
        </Directory>

        ScriptAlias /cgi-bin/ /var/www/cgi-bin/
        <Directory "/var/www/cgi-bin">
                AllowOverride None
                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                AddHandler cgi-script .py
                AddHandler default-handler .html .htm
                Allow from all
        </Directory>
        <Directory "/var/www/run">
                AllowOverride None
                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                AddHandler cgi-script .py
                AddHandler default-handler .html .htm
                Allow from all
        </Directory>
        <Directory "/var/www/tracedecode">
                AllowOverride None
                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                AddHandler cgi-script .py
                AddHandler default-handler .html .htm
                Allow from all
        </Directory>

        # AddHandler mod_python .py

5. Restart apache2
sudo service apache2 restart



https://www.linux.com/blog/configuring-apache2-run-python-scripts

Allow remote SSHas root login

Become root
sudo su

Create password as root
passwd

Modify file /etc/ssh/sshd_config


# Authentication:
LoginGraceTime 120
# PermitRootLogin prohibit-password
PermitRootLogin yes
StrictModes yes

Restart SSH service  

sudo service sshd restart  

Backing up snapshot using LVM

https://www.howtoforge.com/linux_lvm_snapshots

How to remove disk file using pipe to rm command

find . -name "*\.pyc" | xargs rm -f

Adding desktop to Ubuntu 16.04 server

sudo apt-get install ubuntu-desktop 

Adding new disk to Ubuntu 14.04 system.

1. Add new hardware disk to Ubuntu 14.04 system using LVM ( Logical Volume Manager)

• fdisk /dev/sdb
• select new partition "n"
• select primary partition "p"  
• select one partition  "1"
• "cr"
• "cr" 
• write changes to disk "w"

2. Create Physical Volume,  Virtual Group and Logical Volume using LVM

• Make sure LVM is installed on your computer.
  sudo apt-get install lvm2
• Create physical volume "/dev/sdb1"
  pvcreate /dev/sdb1
• Create volume group named "testtool97-disk" and include physical volume /dev/sdb1
  vgcreate testtool97-disk  /dev/sdb1
• Create logical volume named "disk" of size 5.9G and add it to volume group testtool97-disk
  lvcreate -n disk -L 5.9 testtool97-disk

3. Make file system 

• mkfs.ext4 /dev/testtool97-disk/disk 
• mkdir /disk
• vi /etc/fstab 
• add following line to mount file system on "disk" mount point 


• /dev/testtool97-disk/disk /disk               ext4    errors=remount-ro 0       1


• save and quit 

4. Mount directory /disk

•  mount /disk 

Rename all JPG MP4 files in the current directory to date_time file name format.

Rename all files in the currect directory to date_time file name format

sudo exiftool '-filename<CreateDate' -d %y-%m-%d_%H-%M-%S.%%ue  -r -ext JPG  .

Rename files with MOV extention to MP4 extention.

Rename all files with .MOV extention to .MP4 extention.

sudo rename -v 's/\.MOV$/\.MP4/'  *.MOV

Extracting images from video file

Get image from input.flv file at 14.435 sec and save to out.png file

avconv -i input.flv -ss 00:00:14.435 -f image2 -vframes 1 out.png

avconv -i input.flv -ss 00:00:14.435 -f image2 -vframes 1 out.png

Adding text annotations to JPG image.

Adding annotation "Copyright" at lower right corner of image at font size 20, filled with white color and black shadow,  saved to file IMG_ANNOTATED.JPG

sudo convert IMG.JPG  -font Arial -pointsize 20 -draw "gravity SouthEast fill black text 0,12 'Copyright' fill white text 1,11 'Copyright'"  IMG_ANNOTATED.JPG 

Adding GIF image to JPG image with transparent area.

1. Install ImageMagick:
sudo apt-get install imagemagick

2. Using convert command from ImageMagick make white part of Arrow.gif transparent and save in file arrow_transparent.gif :
sudo convert Arrow.gif -fuzz 10% -transparent white arrow_transparent.gif 

3. Merge arrow transparent into IMG.JPG at affset 300,300 and save file in RESULT.JPG file:
sudo convert IMG.JPG -page +300+300 arrow_transparent.gif -flatten RESULT.JPG

How to remove all files which are older than 5 days

How to list all files older than 5 days ?
>  find /path/to/files* -mtime +5

How to delete all files older than 5 days ?
>  find /path/to/files* -mtime +5 -exec rm {} \;

When Ubuntu does not start interfaces from eth0

When Ubuntu after starting does not have eth0, but instead created eth2 etc.
Go to edit file etc/udev/rules.d/70-persistent-net.rules and assign proper eth names to mac adresses.

# PCI device 0x8086:0x100f (e1000)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:aa:80:d7", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.
# PCI device 0x8086:0x100f (e1000)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:aa:80:e1", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"

Remote python debugging using Eclipse

1. Untar file pysrc.tar  into directory p2t

2. Start Debugger Server in Eclipse

3. Insert following code into python source code and execute.

        import sys
        sys.path.append(r'../pysrc')
        import pydevd
        pydevd.settrace('10.51.2.91', port=5678) # IP of your Eclipse machine
or
        pydevd.settrace('10.51.2.91', port=5678, stdoutToServer=True, stderrorToServer=True)

where IP is adress of machine running Eclipse program 

Ubuntu : Bonding interfaces eth1 eth2 eth3 into one logical bond0

Bonding interfaces 

 In the file /etc/network/interfaces 

 # Bonding 
up /sbin/modprobe -o bonding_ext1 bonding mode=4 miimon=500 updelay=0 xmit_hash_policy=layer3+4
up /sbin/ifenslave bond0 eth1 eth2 eth3

Checking if/which interfaces were bonded 
cat /proc/net/bonding/bond0

How to install python as Web executable in Ubuntu 8.04

1. Install Apache2
   > sudo apt-get install apache2
2. Install python apache module
    > sudo apt-get install libapache2-mod-python

3. Modify Apache2 configuration in the file /etc/apache2/sites-available/default
adding

Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
AddHandler mod_python .py
PythonHandler mod_python.publisher
PythonDebug On


4. Restart apache
> sudo /etc/init.d/apache2 restart

5. Create file hello.py  in directory /var/www


def index():
c=  "Hello World"
return c;


6. Start Web browser at URL  http://localhost/hello.py

How to create animation with python and PyODE package.

Falling Boxes in HD.  PyODE animation. from Krzysztof J Pakula on Vimeo.


Instruction for Linux Ubuntu users.

1. You already should have version of Python installed by default on your machine. 

2. Install packages PyODE and cgkit 

    > sudo apt-get install  python-pyode 

    > sudo apt-get install  python-cgkit 

3. Download python script pyode_ex_hd.py .  

4. By executing this python script you will create pyode_ex_hd.rib file 

    > python pyode_ex_hd.py

5. Install Pixie renderman program. ( If you have problem finding renderman install from this deb file) 

6. Download and compile surface shader file  occsurf2.sl    

    > sdrc occsurf2.sl 

7. Render the rib file   

    > rndr pyode_ex_hd.rib  

    Rendering the rib file will create series of picture files in pyode_ex_hd.001.tif , ..., pyode_ex_hd.300.tif
    It will take few hours depending on the speed of your computer.
8. Install ImageMagick on your Ubuntu system
    > sudo apt-get install imagemagick
9. Using ImageMagick Convert all tif files to png format.
    > convert pyode_ex_hd.001.tif  pyode_ex_hd.001.png
       ........
    > convert pyode_ex_hd.300.tif  pyode_ex_hd.300.png     

10. Using VirtualDubMod program create single uncompressed avi file from tif files.

    This step shall be done on Windows machine. 

    You must use vcf configuration file   pyode_ex_hd.vcf 

    >VirtualDubMod   /spyode_ex_hd.vcd  /x

11. Compress avi file to mp4 format using H.264 encoder.   

Testing SOAPVASP interafce Python performance using "timeit"

1. Start SOAPVASP interface on port 7000
$ python interfaceSOAPVASP.py -p 7000

2. Run on the same machine
$ python -m timeit "import http_sender; http_sender.SimpleHTTPSender.send(host
='127.0.0.1', port ='7000', method='GET')"
100 loops, best of 3: 11.5 msec per loop

Password free ssh logging to remote computer

1. Create rsa id
> cd
> ssh-keygen -t rsa

2. Copy rsa id to remote computer as user me
> ssh-copy-id -i ~/.ssh/id_rsa.pub me@10.19.169.5

3. Test by
> ssh me@10.19.169.5

The computer at 10.19.169.5 shall NOT ask you for password

Shell script to execute command on the list of computers

The list of computers is given as a text list of IP adresses named "all.list". Each IP in saparate line

To execute commands on each computer create file all.sh with following text
for i in `cat all.list | awk '{ print $i}'` ; do echo $i; ssh $i $1 ; done

Execute commands by
> source ./all.sh "ls -la"

To execute command as root on remote computer with ip 10.19.148.65 using ssh

To execute command as root on remote computer with ip 10.19.168.65
> ssh root@10.19.148.65 "ls -la"

To execute text replacement on remote computer using perl script
> ssh root@10.19.148.65 "perl -p -e 's/oldtext/newtext/g' oldfile >newfile"

How to replace text in many files using single perl command

To replace text "localhost" to "localnet" in all files with extension text execute following
> perl -p -e "s/localhost/localnet/g" *.txt

To add new line after new text "localnet" use new line code \x0a
> perl -p -e "s/localhost/localnet\x0anew line/g" *.txt

To insert TAB in replaced text use code \x09
> perl -p -e "s/localhost/localnet\x0anew line\x09rest of line after tab/g" *.txt