xrdp is a free open-source remote desktop server for Linux.
Installing xrdp on CentOS might be a little tricky since CentOS repositories does not contain the xrdp package.
Even the EPEL repository (Extra Packages Enterprise Linux) only contains an old version of xrdp.
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DevOps/IT Specialist, Musician.
IT Manager – Faculty of Exact Sciences, Bar-Ilan University
Personal Website
CentOS Tomcat
centos tomcat
“Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies. The Java Servlet and JavaServer Pages specifications are developed under the Java Community Process.” from Tomcat homepage.
before we’ll continue the installation of Tomcat, the JDK (Java Development Kit) should be installed on your CentOS machine. to check for Java support use the command:
java -version
if bash returns ‘command not found‘ then continue to the next step and install the JDK, else skip the step and continue to Tomcat server installation.
To install the jdk we have 2 options:
I’ll explore both:
For beginners and testing purposes you should go with this option.
Why should I use the Oracle JDK over the OpenJDK, or vice-versa? [closed]
The command to install JDK using YUM is very simple:
yum install java
Check you have installed it right:
Download your required JDK here.
Note: I can’t give you an WGET command to download, because you need to Accept License Agreement before downloading any file.
You can download and install using the RPM or the tar.gz (both with x86 or x64) on your CentOS machine:
In case of our CentOS we can download and install the .rpm file or the .tar.gz file.
RPM can be installed ONLY by the root.
TAR.GZ can be installed be any user on the computer.
make sure to uninstall older installations (if any):
rpm –e <package name>
To install the jdk using the downloaded rpm use the rpm command:
rpm –ivh jdk-7u45-linux-x64.rpm
If you just want to upgrade a package you’ve already installed use the -Uvh parameter.
rpm –Uvh jdk-7u45-linux-x64.rpm
Delete the .rpm file if you want to save disk space.
Read more about installation of Oracle Java on Centos here on ItekBlog
Use alternatives :
alternatives –install /usr/bin/java java /usr/java/latest/jre/bin/java 20000
alternatives –install /usr/bin/javaws javaws /usr/java/latest/jre/bin/javaws 20000
and config your default jdk (if you have more then one) using:
using:
alternatives –config java
Just as in the first step: type java -version to see if your have jdk installed.
The advantage of tar.gz installation of the JDK is that we can able to install multiple version of java if required.
The archive can be installed by anyone (not only root users), in any location that you can write to. However, only the root user can install the JDK into the system location.
You need to unpack the .tar.gz file (using tar -xzf) into the the location where you would like the JDK to be installed.
Unpack the tarball and install the jdk:
tar zxvf jdk-7u<version>-linux-i586.tar.gz
Delete the .tar.gz file if you want to save disk space.
Use alternatives :
alternatives –install /usr/bin/java java /path/to/jdk1.7.0_45/bin/java 2
alternatives –config java
read more about installation of jdk in the oracle documentation.
for extended installation tutorial read this post by adam in this blog.
read more on What is the difference between jdk 1.6 and 1.7 ?
1 | JAVA_HOME |
is a
1 | environment |
variable (in Unix terminologies), or a PATH variable (in Windows terminology) you need to create to point to where Java is installed. ($JAVA_HOME/bin/java should execute the Java runtime).
To set it for your current session type at bash:
export JAVA_HOME=/usr/java/jdk1.7.0_05
export PATH=$PATH:$JAVA_HOME/bin
To set the JAVA_HOME permanently we need to add the commands to the ~/.bash_profile file of the user.
We can also add it /etc/profile and then source it to give to all users.
use the echo command to check you’ve configured the variables:
echo $JAVA_HOME
echo $PATH
After we have java installed and tested we can continue to the installation of the Tomcat server.
Since Apache Tomcat is distributed as binaries, all you have to do is to download it and start it.
Download apache-tomcat-x.x.xx.tar.gz (latest version or any) from Apache Tomcat Homepage
I’ll go with the tomcat 8 – tar.gz package.
centos tomcat
and using command:
cd /usr/share
wget http://apache.spd.co.il/tomcat/tomcat-8/v8.0.0-RC10/bin/apache-tomcat-8.0.0-RC10.tar.gz
verify and extract the download using::
md5sum apache-tomcat-8.0.0-RC10.tar.gz
tar xvzf apache-tomcat-8.0.0-RC10.tar.gz
and I have a /usr/share/apache-tomcat-8.0.0-RC10 folder now.
Tomcat by default start on port 8080 you can start the server now by typing at bash:
cd apache-tomcat-8.0.0-RC10
./bin/startup.sh
Now Access the tomcat by connecting your server with a web browser on port 8080.
http://localhost:8080
If you cannot access the above Tomcat page, make sure to stop iptables (since CentOS has iptables on by default set to block the Tomcat’s default listening port 8080).
service iptables stop
to permanently disable iptables (NOT RECOMMENDED AT ALL) use:
chkconfig iptables off
Locate server.xml in {Tomcat installation folder}/conf/ which is at /usr/share/apache-tomcat-8.0.0-RC10/conf in our case
Find the following:
<!-- Define a non-SSL HTTP/1.1 Connector on port 8180 -->
<Connector port="8080" maxHttpHeaderSize="8192"
maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
enableLookups="false" redirectPort="8443" acceptCount="100"
connectionTimeout="20000" disableUploadTimeout="true" />
and change the 8080 port to your required port.
To start the tomcat service on system boot create the file /etc/init.d/tomcat8 (I am using vi /etc/init.d/tomcat8) and fill it with:
#!/bin/bash # description: Tomcat Start Stop Restart # processname: tomcat # chkconfig: 234 20 80 JAVA_HOME=/usr/java/jdk1.7.0_05 export JAVA_HOME PATH=$JAVA_HOME/bin:$PATH export PATH CATALINA_HOME=/usr/share/apache-tomcat-8.0.0-RC10 case $1 in start) sh $CATALINA_HOME/bin/startup.sh ;; stop) sh $CATALINA_HOME/bin/shutdown.sh ;; restart) sh $CATALINA_HOME/bin/shutdown.sh sh $CATALINA_HOME/bin/startup.sh ;; esac exit 0
Now set the permissions on the file and the catalina.sh file:
chmod a+x /etc/init.d/tomcat8 chmod a+x /usr/share/apache-tomcat-8.0.0-RC10/bin/catalina.sh
to start/stop/restart the service use:
service tomcat8 start service tomcat8 restart service tomcat8 stop
to start the service on boot use:
chkconfig --add tomcat8 chkconfig tomcat8 on
to disable it later you can use off instead of on:
chkconfig tomcat8 off
That’s it! you have your CentOS Tomcat server working and runing…
CentOS G-WAN server
G-WAN is a web server with scripts in Asm, C, C++, C#, D, Go, Java, Javascript, Lua, Objective-C, Perl, PHP, Python, Ruby and Scala.
G-WAN better uses CPU Cores
to make the Internet of Things
fly thousand times higher !Leverage legacy servers and
low-consumption CPUs to
do more with less!
G-WAN works best on Linux distributions like Debian or CentOS, both of which offer ‘Desktop’ and ‘Server’ flavors.
CentOS G-WAN installation instructions
choose a location for your installation. for demonstration purposes we’ll install G-WAN to /opt
cd /opt wget http://gwan.com/archives/gwan_linux64-bit.tar.bz2 tar -xjf gwan_linux64-bit.tar.bz2; cd gwan_linux64-bit sudo ./gwan
centos g-wan
use the 32bit version instead (http://gwan.com/archives/gwan_linux32-bit.tar.bz2) if you need.
Then, type http://localhost:8080/ in your browser
and play with the/gwan/.../csp samples.
If you want to install more Programming Languages read the FAQ – Setup of Programming Languages
To install all 15 languages using the bash script donated by generous user on many Linux distributions (Debian, LinuxMint, CentOS, Fedora, RedHat, Manjaro, Arch Linux and Bridge) use:
cd /opt
wget http://www.as2.com/linux/tools/G-WAN_full-install.tar.bz2
tar -xjf G-WAN_full-install.tar.bz2
./G-WAN_full-install
The installation menu is available in English, German, French and Spanish!
To start G-WAN as a service (make it start automatically at boot time) use this instructions
with one exception for CentOS in the manual:
instead of:
sudo update-rc.d gwan defaults 95 5
use:
sudo chkconfig gwan on
and you don’t need to restart.
check the API and Frequently Asked Questions.
Stackoverflow lists many more examples and will let you search for replies to common questions.
And that’s it. you have G-WAN server.
“iptables is a user space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores.
Different kernel modules and programs are currently used for different protocols; iptables applies to IPv4, ip6tables to IPv6, arptables to ARP, and ebtables to Ethernet frames.”
In this tutorial I will give a few essential examples of how to use iptables on CentOS
Continue reading
DevOps/IT Specialist, Musician.
IT Manager – Faculty of Exact Sciences, Bar-Ilan University
Personal Website
SSL handshake failed: SSL error: Key usage violation in certificate has been detected.
SSL handshake failed: SSL error: Key usage violation in certificate has been detected CentOS.
You may experience the issue if both of the following conditions are met:
GnuTLS library is an open-source alternative to OpenSSL. Most Subversion clients for Windows are built against OpenSSL and are not affected by this issue. While some Subversion packages (available mostly on Linux-based operating systems – The subversion that comes with EL 6 is linked against GnuTLS which is a change from older releases which linked against OpenSSL) are built against GnuTLS and are affected.
The server is using an SSL cert was created with the ‘key usage’ extension, and the client is using the gnutls SSL library which doesn’t understand the extension. The solution is either to have the client use the openssl library or to have the server use a cert that doesn’t use the ‘key usage’ extension.
It’s recommended to fix the issue on your server side, but you can workaround it from the client side too.
Here is what visualsvn.com say:
It’s not recommended to use a self-signed certificate in a production environment. We advise to use a certificate issued by your domain or a third-party certificate authority instead of a self-signed one.
If you have to use a self-signed certificate please follow the instruction to generate a cerificate without specifying ‘Key Usage’ extension:
Add the following registry value to the Windows registry:
for 32-bit system:
[HKEY_LOCAL_MACHINE\SOFTWARE\VisualSVN\VisualSVN Server]
“CreateGnuTLSCompatibleCertificate”=dword:00000001
for 64-bit system:
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\VisualSVN\ VisualSVN Server]
“CreateGnuTLSCompatibleCertificate”=dword:00000001
Start VisualSVN Server Manager.
Go to Action | Properties | Certificate.
Click Change certificate… and follow the wizard instructions to generate a new self-signed certificate.
The certificate will be generated without the ‘Key Usage’ extension and will be compatible both with GnuTLS and OpenSSL.
The options for client side fix are:
That’s it.
If you are like me, using VMWare workstation on Linux (CentOS 6.4), and you want to start your virtual machines on boot, I have the answer.
VMWare Workstation start on boot CentOS
add to the end of the following file:
/etc/rc.d/rc.local
the following:
vmrun -T ws start /path/to/machine.vmx nogui
create new line for each machine you want to start on boot.
that’s it! that how you run vmware workstation start on boot centos
That’s it.
So you want to build your first django centos 6.4 based web site? This is quite easy to install and configure. I’ll cover how to install Python/Django on your centos.
“Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Its syntax is said to be clear and expressive.” from Wikipedia.
Visit http://www.python.org/
“Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design.” from https://www.djangoproject.com/
you may need the EPEL repositories for Centos.
1 2 3 4 |
cd /opt/ wget http://mirrors.nl.eu.kernel.org/fedora-epel/6/i386/epel-release-6-8.noarch.rpm rpm -Uvh epel-release-6-8.noarch.rpm rm epel-release-6-8.noarch.rpm -f |
cd /opt/ wget http://mirrors.nl.eu.kernel.org/fedora-epel/6/i386/epel-release-6-8.noarch.rpm rpm -Uvh epel-release-6-8.noarch.rpm rm epel-release-6-8.noarch.rpm -f
Simple as:
1 |
yum install python
|
yum install python
test python by typing: “python” and you should see something similar to: (CTRL+D to exit)
At the time of writing (September 30 2013), the version of python@EPEL is 2.6.6
Django works with any Python version from 2.6.5 to 2.7. It also features experimental support for versions 3.2 and 3.3. All these versions of Python include a lightweight database called SQLite so you won’t need to set up a database just yet unless you need other SQL
Django works with several DB engines. for simplicity, Install SQLite:
yum install sqlite
If you need other SQL Server else then SQLite, you can follow:
MySQL/MongoDB/CouchDB on RHEL/Centos 6.3
If you don’t need SQL and you installed Python 2.5 or later, you can skip this step for now.
You can install using EPEL repositories any yum (like in the old article I wrote), but I recommend to use the easy_install method from the python-setuptools package, which I’ll show next:
1 2 |
yum install python-setuptools
easy_install django
|
yum install python-setuptools easy_install django
Test Django by typing python on your command and then:
1 2 |
import django print django.get_version() |
import django print django.get_version()
As you can see, the RPM version is version 1.5.4, while the current release in the EPEL version is 1.3.1. Internationalization: in template code is not available in 1.3.1 for example but only from Django 1.4
From the command, cd into a directory where you’d like to store your app, then run the following command:
1 2 |
django-admin.py startproject mysite
cd mysite
|
django-admin.py startproject mysite cd mysite
Note: if you are installing Django using EPEL repos, the command will be django-admin and not django-admin.py.
1 |
python manage.py runserver |
python manage.py runserver
You’ve started the Django development server, a lightweight Web server – easier to startwithout having to deal with configuring a production server — such as Apache — until you’re ready for production.
Browse to http://127.0.0.1:8000/ with your Web browser. You’ll see a “Welcome to Django” page. It worked!
To change port:
1 |
python manage.py runserver 8080
|
python manage.py runserver 8080
If you need to start the server to answer not only locally, use:
1 |
python manage.py runserver 0.0.0.0:8000
|
python manage.py runserver 0.0.0.0:8000
Remember: Apache loads Django environment when starting and keep running it even when source is changed! I suggest you to use Django ‘runserver’ (which automatically restarts on source code changes) in development sessions, unless you need some Apache-specific features.
Edit mysite/settings.py. It’s a normal Python module with module-level variables representing Django settings.
Help here.
To run your Django application inside apache – use either mod_python or mod_wsgi, Support for mod_python will be deprecated in a future release of Django. If you are configuring a new deployment, you are strongly encouraged to consider using mod_wsgi or any of the other supported backends.
For this to work, you must have apache installed and configured.
1 |
yum install mod_python
|
yum install mod_python
you need to configure you apache/VirtualHost to:
AddHandler mod_python .py
PythonHandler mod_python.publisher | .py
AddHandler mod_python .psp .psp_
PythonHandler mod_python.psp | .psp .psp_
PythonDebug On</pre>
[/code]
<h3>Testing mod_python</h3>
Create a '<em>test.py'</em> file in your apache server. put inside:
[code lang="py"]<% req.write("Hello World!") %>[/code]
and browse to www.your.server/test.py and you should see the "Hello World!" there.
<h3>Django using mod_python</h3>
Edit your <tt>httpd.conf</tt> file:
[code lang="apache"]
<pre><Location "/mysite/">
SetHandler python-program
PythonHandler django.core.handlers.modpython
SetEnv DJANGO_SETTINGS_MODULE mysite.settings
PythonOption django.root /mysite
PythonDebug On
</Location>
Deploying Django with Apache and mod_wsgi is the recommended way to get Django into production.
1 |
yum install mod_wsgi
|
yum install mod_wsgi
to use mod_wsgi, create an apache folder inside your project and create a django.wsgi file:
import os, sys
sys.path.append('/var/www/django')
sys.path.append('/var/www/django/mysite')
os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings'
import django.core.handlers.wsgi
application = django.core.handlers.wsgi.WSGIHandler()
and configure your apache with:
<VirtualHost *:80>
ServerName www.example.com
ServerAlias www.example.com
WSGIScriptAlias / /var/www/django/mysite/apache/django.wsgi
# Alias /robots.txt /var/www/django/mysite/static/robots.txt
# Alias /favicon.ico /var/www/django/mysite/static/favicon.ico
Alias /static/admin/ /usr/lib/python2.6/site-packages/django/contrib/admin/media/
Alias /static/ /var/www/django/mysite/static/
Alias /media/ /var/www/django/mysite/media/
<Directory /var/www/django/mysite>
Order allow,deny
Allow from all
</Directory>
<Directory /var/www/django/mysite/media>
Order deny,allow
Allow from all
</Directory>
<Directory /var/www/django/mysite/static>
Order deny,allow
Allow from all
</Directory>
</VirtualHost>
read more on: multiple django sites with apache & mod_wsgi
You’ve Python / Django installed on your Centos 6.4 and a new project template waiting for you to work on.
* this article is an edited version of an older article.
if you have installed new setup of centos or you haven’t installed yet, you need make, gcc, kernel-devel..
If you want to add the RPMForge repo to your CentOS, use the following instructions
cd /tmp
# for 32 bit:
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.i686.rpm
# for 64 bit:
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
Note: Visit here to see if newer version exist.
rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
# for 32 bit:
rpm -i rpmforge-release-0.5.3-1.el6.rf.i686.rpm
# for 64 bit:
rpm -i rpmforge-release-0.5.3-1.el6.rf.x86_64.rpmyum clean all
If you want, you can enable the extra repo using:
cd /etc/yum.repos.d
edit using vi/vom/mc rpmforge.repo:
change the enabled flag to enabled=1 in the section [rpmforge-extras].
yum update
That’s it!
If you want to update your Git to newer version then on CentOS repository, use the following instructions
cd /tmp
# for 32 bit:
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.i686.rpm
# for 64 bit:
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
Note: Visit here to see if newer version exist.
rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
# for 32 bit:
rpm -i rpmforge-release-0.5.3-1.el6.rf.i686.rpm
# for 64 bit:
rpm -i rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
yum clean all
cd /etc/yum.repos.d
edit using vi/vom/mc rpmforge.repo:
change the enabled flag to enabled=1 in the section [rpmforge-extras].
yum update git
yum provides git will help you see all versions available.
git –version
Will show you have the new release installed. (1.7.11.3 for me)
That’s it!
You need to have a public key. If you haven’t generated keys before use:
ssh-keygen -t rsa
copy ssh public key is very simple. there are some ways to achieve this:
ssh-copy-id user@host
with this very simple command you can copy your public key to any user@host combination
scp .ssh/id_rsa.pub user@host2:.ssh/authorized_keys
cd ~/ before.
The different is that scp will create a new file called authorized_keys while ssh-copy-id will add to id.
in this article: Python vs PyPy I’ll explain how-to install both compilers (Python (CPython) and PyPy) on CentOS and the difference between them.
The Download section of the Python official website (python.org) include list of several Alternative Implementations for python complier. some of them for Linux, some for Windows (.NET) and others.
I am going to review the default Python compiler vs PyPy on my CentOS 6.x machine.
yum install python
From Official website:
Python is a programming language that lets you work more quickly and integrate your systems more effectively. You can learn to use Python and see almost immediate gains in productivity and lower maintenance costs.
Python (nicknamed CPython) is the default Python Compiler you get with you installing Python.
Create a file named ‘example.py‘ and fill it with:
print 'Hello, world!'
and type on bash:
python example.py
Note: you can also insert the following line as the first line in your .py file and then chmod +x this file to execute it as script:
#!/usr/lib/env python
print “Hello, world!”
and then on bash:
chmod +x example.py
and you can run the script (code) using:
./example.py
A fast python implementation with a JIT compiler (generate native code on the fly) written in RPython and currently translated partly to C.
Arguments against PyPy compiled in Python are everywhere, but when C compiler gcc is implemented in C, is there any reason for the Python compiler to not be written in Python?
From Wikipedia:
PyPy is a Python interpreter and just-in-time compiler. PyPy focuses on speed, efficiency and compatibility with the original CPython interpreter.[1]
PyPy started out as a Python interpreter written in the Python language itself. Current PyPy versions are translated from RPython to C code and compiled. The PyPy JIT compiler is capable of turning Python code into machine code at run time.
The mission of PyPy is:
We aim to provide:
- a common translation and support framework for producing implementations of dynamic languages, emphasizing a clean separation between language specification and implementation aspects. We call this the RPython toolchain.
- a compliant, flexible and fast implementation of the Python Language which uses the above toolchain to enable new advanced high-level features without having to encode the low-level details. We call this PyPy.
By separating concerns in this way, our implementation of Python – and other dynamic languages – is able to automatically generate a Just-in-Time compiler for any dynamic language. It also allows a mix-and-match approach to implementation decisions, including many that have historically been outside of a user’s control, such as target platform, memory and threading models, garbage collection strategies, and optimizations applied, including whether or not to have a JIT in the first place.
How can it possibly beat CPython?
Manual memory management (which is what CPython does with its counting) can be slower than automatic management in some cases.
Limitations in the implementation of the CPython interpreter preclude certain optimisations that PyPy can do (eg. fine grained locks).
The JIT. Being able to on the fly confirm the type of an object can save you the need to do multiple pointer dereferences to finally arrive at the method you want to call.
yum install pypy
To use pypy instead of your default CPython compiler you need to run your .py file with the pypy compiler.
to use pypy compiler you type at bash:
and type on bash:
pypy myapp.py
Python compiler (CPython) is the default and probably the safe choice so most python applications and modules will work; where PyPy can break some.
You should play with them both. Install them both on your CentOS and test / benchmark your applications using both compilers.
PyPy can rebust your web applcations (or any other code).
For example, Django app can be run on top of PyPy, with drawbacks.