Nice Technical Stuff

How to start GUI from Linux Shell

nicetechstuff — Fri, 12 Jun 2009 05:12:20 +0000

To start GUI type below command

$startx

Vncserver commands

nicetechstuff — Thu, 28 May 2009 05:12:22 +0000

Vncserver is a perl script which is used to start a desktop. VNC stands for Virtual network computing.

To start the session type below command at the prompt

vncserver

To change the password you have two options

Option 1:

Type vncpasswd
Enter the new password

Option 2:

Navigate to $HOME and remove .vnc folder. For example, rm –rf /root/.vnc here $HOME is /root

To kill the existing session

vncserver –kill :6

Here 6 is the display number

How to display startup message (Remote desktop)

nicetechstuff — Wed, 27 May 2009 11:27:41 +0000

Sometimes it was required to display some message when you log in to the windows machine using remote desktop. For example, Logoff when you disconnect or Admin is watching, do not delete content etc

Follow below steps,

Navigate to Settings > Control Panel > Local Security Settings > Local Policies > Security Options
Provide title for the window

Interactive logon: Message title for users attempting to log on
Provide message to be displayed

Interactive logon: Message text for users attempting to log on

Eclipse Shortcuts

nicetechstuff — Thu, 21 May 2009 12:15:16 +0000

Command	Description
Alt + Ctrl + UP/DOWN arrow	Select the content(where cursor is positioned) and copy it to the previous or next line
Alt + Up / Down arrow	Select the content(where cursor is positioned) and move it to the previous or next line
Alt + Shift + C	Change method signature
Alt + Shift + D	Invokes debug as box
Alt + Shift + L	Extract to local variable
Alt + Shift + M	Extract to method
Alt + Shift + R	Rename
Alt + Shift + X	Invokes run as
Alt + Shift + W	Synchronize the current file with the Navigator or Package explorer etc.,
Class Name + Ctrl + space	Adds default constructor
Ctrl + F3 (or) Ctrl + O	Open declarations
Ctrl + .	To go directly to the next warning or error in your current source file
Ctrl + /	Line comment
Ctrl + 1	Quick fix
Ctrl + 2 + R	Select the variable and press Ctrl + 2 + R. Renaming the selected variable will change all the occurrences
Ctrl + E	Open Editor and you can select any open file
Ctrl + F4	Close one source window.
Ctrl + H	Search & Replace
Ctrl + i	Good indentation of selected code
Ctrl + L	Go to line number
Ctrl + PgUp / PgDn	Changes focus to previous/next editor respectively..
Ctrl + Q	Control goes to last edit.
Ctrl + Shift + Arrow-up (or) Ctrl + Shift + Arrow-down	Jumping from method to method:
Ctrl + Shift + F4	Close all opened editors
Ctrl + Shift + F4	Close all source windows
Ctrl + Shift + L	Displays all short cuts
Ctrl + Shift + M	Add import class
Ctrl + Shift + O	Organize imports
Ctrl + Shift + R	Opens a named resource in the project
Ctrl + Shift + T	Open type
Ctrl + Shift + X	To upper case
Ctrl + Shift + Y	To lower case
Rename compilation unit	Sometimes if your java file name does not match with class name, you can click the error marker in the left margin on the line with the class name and then double-click ‘Rename compilation unit etc.’
Syso	Type syso and press enter. It prints system.out.println automatically

Disabling Case Sensitivity in Apache

nicetechstuff — Thu, 21 May 2009 10:34:12 +0000

Apache is case sensitive. When you application is hosted in case-insensitive webserver(like IIS) and moved to case-sensitive webserver (like Apache) you may get some problems related to non availability of URLS(HTTP 404 error). Apach provides a module which helps to make URLs case-insensitive.

Open httpd.conf(your apache configuration file) and find out the below line

LoadModule speling_module modules/mod_speling.so

If the above module is avilable with your apache, turn on the CheckSpelling directive

CheckSpelling On

How to know whether a library is built on 32-bit or 64-bit?

nicetechstuff — Wed, 20 May 2009 08:48:39 +0000

Type below command at shell

file /usr/local/apache2.2.11/lib/libapr-1.so.0.3.3

The output of above command is,

/usr/local/apache2.2.11/lib/libapr-1.so.0.3.3: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), not stripped

The output tells that the libapr-1.so.0.3.3 file is built on 32-bit machines

Frequently used Linux Commands

nicetechstuff — Wed, 20 May 2009 08:32:46 +0000

I’m sharing some of the Linux commands that I use frequently

Basic Commands

Command	Description
ll	It is equivalent to ls -l and lists the files in the directory
ctrl + l	It clears the display
ps -el \| grep java	list information about the java process
ps -el \| grep -i java	-i indicates ignores case sensitive
echo $PATH	prints value of the environment variable PATH
export PATH=/usr/bin:$PATH	Sets the PATH environment variable with /usr/bin
scp /opt/etc/* root@node2:/opt/test/	Remote copy. It copies all the files in /opt/etc to node02 /opt/test directory. To do this you need node2 root password
rm -rf test	Removes test directory recursively(-r) and forcefully (-f)

Apache Related

Command	Description
/usr/local/apache2/bin/httpd -V	Displays apache version
/usr/local/apache2/bin/httpd -k [start/stop/restart]	Starts/stops/restarts the apache
httpd -t -c /usr/local/apache2/conf/httpd.conf	Verifies the syntax of httpd.conf
/usr/local/apache2/bin/httpd -X	Starts apache in debug mode

RPM

Command	Description
rpm -ivh j2sdk-1_4_2_07-linux-i586.rpm	Installs a rpm
rpm -qa \| grep httpd	List the existing rpms

System

Command	Description
hostname	Prints machine name
hostname -i	ip address of the machine
ifconfig	Prints ip address along with other information like subnet mask etc..
cat /proc/version	Linux version
cat/proc/cpuinfo	CPU information
cat /etc/*release	Shows the Linux release information
services iptables stop service ip6tables stop	Disables the firewall
java -version	Java version information
netstat -lnp \| grep mysql	Displays the mysql server port information
netstat -an \| grep :80 \| sort	Displays the connection details(sorted) to the web server. In this case web server is running on port 80
lsof -p lsof -p 3308	This command displays the list of libraries used by a process. For example, if apache process id is 3008, then lsof -p 3008 lists the libraries currently apache is using. In windows we can get this information with process explorer.

How to monitor Apache server status?

nicetechstuff — Wed, 20 May 2009 06:52:19 +0000

There is a built in module mod_status available in apache which helps to get server status from a web browser

To monitor Apache webserver,

Open httpd.conf(Placed at /conf/httpd.conf)

vi httpd.conf

Set the Location directive as below. It will alow only from 192.13.24.57

SetHandler server-status

Order Deny,Allow

Deny from all

Allow from 192.13.24.57

Set ExtendendStatus to on

ExtendedStatus on

Save the httpd.conf and restart the webserver

Now you can monitor your apache webserver with http://servername/server-status from 192.13.24.57 browser