Recompile virtual box kernel modules after kernel update

If Virtualbox or guest aditions are not starting ater a kernel update, just recompile the kernel modules:


o On a Virtualbox server

    /etc/init.d/vboxdrv setup

o On a Virtualbox guest

    /etc/init.d/vboxadd setup

Grub2: Set default boot option

o Get the string of the menu entry you desire to be default

  fgrep menuentry /boot/grub/grub.cfg
  ...
  menuentry "Some OS" {
  ...
 
o Add menu entry to /etc/default/grub
  
  vi /etc/default/grub 
  GRUB_DEFAULT="Some OS"

o Update grub

  update-grub

Enhance Adobe flash player performance in Linux

These settings will slightly improve the performance of the adobe flash
plugin:

o Customize /etc/X11/xorg.conf

     

  Section "Extensions"
    # for 3D, alpha desktop effects
    Option "Composite" "Enable"
  EndSection

  Section "DRI"
    # helps flash performance
    Mode 0666
  EndSection

o Override GPU Validation

   - Sytem wide

    sudo mkdir /etc/adobe
    echo "OverrideGPUValidation=true" > /etc/adobe/mms.cfg

- Or user wide

    echo OverrideGPUValidation=true > ~/.adobe/mms.cfg

Get SOAP communication using tcpdump

Assume you have a Tomcat running on localhost on port 8080 and want see the content of the SOAP messages of the communication:

tcpdump -i lo0 -A -s 1024 -l 'dst host localhost and port 8080'

Drop Oracle Database

Since 10g, It is possible to drop a database in Oracle 10g with the new SQL statement drop database.

The command gets rid of datafiles online redo log files, controlfiles and spfile:

sqlplus / as sysdba

shutdown abort;

startup mount exclusive restrict;

drop database;

exit

Debian Squeeze: Black screen or freeze on the console after stopping Xserver

Atom powered device

Solution -- add i915.modeset=0 to kernel options in Grub

JayBird - Firebird JDBC link

Get the required JAR from http://www.firebirdsql.org/index.php?op=files&id=jaybird

/**

*

*/

package link.db.my;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Properties;

import org.apache.log4j.Logger;

/**

* @author E. Kaparulin

*/

public class JayBird {

        private Connection conn = null;

        private String Url = "jdbc:firebirdsql:127.0.0.1/3050:mydb";

        private String dbUserName = "user";

        private String dbUserPass = "password";

        private String dbCharSet = "ASCII";

        static final Logger logger = Logger.getLogger("org.firebirdsql");

        public JayBird() {

                System.setProperty("FBLog4j", "true");

                Properties props = new Properties();

                props.setProperty("user", dbUserName);

                props.setProperty("password", dbUserPass);

                props.setProperty("encoding", dbCharSet);

                try {

                        Class.forName("org.firebirdsql.jdbc.FBDriver");

                        try {

                                conn = DriverManager.getConnection(Url, props);

                        } catch (SQLException e) {

                                logger.fatal(e.getMessage());

                        }

                } catch (ClassNotFoundException e) {

                        logger.fatal(e.getMessage());

                }

        }

        private Connection getConnection(){

                return conn;

        }

        public int UpdateQuery(String Query) throws SQLException {

                int ret = -1;

                Connection sqlConn = getConnection();

                Statement Statement = sqlConn.createStatement();

                ret = Statement.executeUpdate(Query);

                Statement.close();

                return ret;

        }

        public ResultSet SelectQuery(String Query) throws SQLException {

                Connection sqlConn = getConnection();

                Statement Statement = sqlConn.createStatement();

                ResultSet rs = Statement.executeQuery(Query);

                return rs;

        }

}

Get properties file from WEB-INF/classes

        PropertyResourceBundle   p = (PropertyResourceBundle)           
         ResourceBundle.getBundle(CONF_FILE);

        String myValue = p.getString("myKey");

Trim String (remove tabs and white spaces)

        private String trimValue(String inputStr) {

                String patternStr = "(( |\t)*$|^( |\t)*)";

                String replacementStr = "";

                // Compile regular expression

                Pattern pattern = Pattern.compile(patternStr);

                // Replace all occurrences of pattern in input

                Matcher matcher = pattern.matcher(inputStr);

                return matcher.replaceAll(replacementStr);

        }

Calculate a MD5 sum of a string

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

   public String getMD5(String input) {

        try {

            MessageDigest md = MessageDigest.getInstance("MD5");

            byte[] messageDigest = md.digest(input.getBytes());

            BigInteger number = new BigInteger(1, messageDigest);

            String hashtext = number.toString(16);

            // Now we need to zero pad it if you actually want the full 32 chars.

            while (hashtext.length() < 32) {

                hashtext = "0" + hashtext;

            }

            return hashtext;

        }

        catch (NoSuchAlgorithmException e) {

            throw new RuntimeException(e);

        }

    }

Create a random string

import java.util.Random;

/**

* @author E. Kaparulin

*/

public class RandomString {

        private final char[] alphanumeric=alphanumeric();

            private final Random rand;

            public RandomString(){this(null);}

            public RandomString(Random rand){

              this.rand=(rand!=null) ? rand : new Random();

            }

            public String get(int len){

                StringBuffer out=new StringBuffer();

                while(out.length() < len){

                    int idx=Math.abs(( rand.nextInt() % alphanumeric.length ));

                    out.append(alphanumeric[idx]);

                }

                return out.toString();

            }

            // create alphanumeric char array

            private char[] alphanumeric(){

                StringBuffer buf=new StringBuffer(128);

                for(int i=48; i<= 57;i++)buf.append((char)i); // 0-9

                for(int i=65; i<= 90;i++)buf.append((char)i); // A-Z

                for(int i=97; i<=122;i++)buf.append((char)i); // a-z

                return buf.toString().toCharArray();

            }

}

Simple SMTP Email

import java.io.BufferedReader;

import java.io.DataOutputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.Socket;

public class SmtpSimple {

        private DataOutputStream os = null;

        private BufferedReader is = null;

        private String sRt = "";

        public synchronized final String sendEmail(

                        String sSmtpServer,String sFromAdr,String sToAdr,String sSubject,String sText)

                        throws IOException, Exception {

                Socket so = null;

                try {

                        sRt = "";

                        if (null == sSmtpServer

                                        || 0 >= sSmtpServer.length()

                                        || null == sFromAdr

                                        || 0 >= sFromAdr.length()

                                        || null == sToAdr

                                        || 0 >= sToAdr.length()

                                        || ((null == sSubject || 0 >= sSubject.length()) && (null == sText || 0 >= sText

                                                        .length())))

                                throw new Exception(

                                                "Invalid Parameters for SmtpSimple.sendEmail().");

                        so = new Socket(sSmtpServer, 25);

                        os = new DataOutputStream(so.getOutputStream());

                        is = new BufferedReader(new InputStreamReader(so.getInputStream()));

                        so.setSoTimeout(10000);

                       

                        writeRead(true, "220", null);

                        writeRead(true, "250", "HELO " + sSmtpServer + "\n");

                        writeRead(true, "250", "RSET\n");

                        writeRead(true, "250", "MAIL FROM:<" + sFromAdr + ">\n");

                        writeRead(true, "250", "RCPT TO:<" + sToAdr + ">\n");

                        writeRead(true, "354", "DATA\n");

                        writeRead(false, null, "To: " + sToAdr + "\n" );

                        writeRead(false, null, "From: " + sFromAdr + "\n");

                        writeRead(false, null, "Subject: " + sSubject + "\n");

                        writeRead(false, null, "Mime-Version: 1.0\n");

                        writeRead(false, null, "Content-Type: text/plain; charset=\"iso-8859-1\"\n");

                        //writeRead(false, null, "Content-Transfer-Encoding: quoted-printable\n\n");

                        writeRead(false, null, "Content-Transfer-Encoding: 7bit\n\n");

                        writeRead(false, null, sText + "\n");

                        writeRead(true, "250", ".\n");

                        writeRead(true, "221", "QUIT\n");

                        return sRt;

                } finally {

                        if (is != null)

                                try {

                                        is.close();

                                } catch (Exception ex) {

                                }

                        if (os != null)

                                try {

                                        os.close();

                                } catch (Exception ex) {

                                }

                        if (so != null)

                                try {

                                        so.close();

                                } catch (Exception ex) {

                                }

                        is = null;

                        os = null;

                }

        }

        private final void writeRead(boolean bReadAnswer,

                        String sAnswerMustStartWith, String sWrite) throws IOException,

                        Exception {

                if (null != sWrite && 0 < sWrite.length()) {

                        sRt += sWrite;

                        os.writeBytes(sWrite);

                }

                if (bReadAnswer) {

                        String sRd = is.readLine() + "\n";

                        sRt += sRd;

                        if (null != sAnswerMustStartWith

                                        && 0 < sAnswerMustStartWith.length()

                                        && !sRd.startsWith(sAnswerMustStartWith))

                                throw new Exception(sRt);

                }

        }

}

Parse XML file

DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();

DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();

Document myXML = docBuilder.parse(xmlFile);

// normalize text representation

myXML.getDocumentElement().normalize ();

//System.out.println ("Root element of the doc is " + myXML.getDocumentElement().getNodeName());

// Dive into XML Structure

NodeList myNode =  myXML.getDocumentElement().getChildNodes();

for(int i=0;i<myNode.getLength();i++) { …

Generate a random number from a range

      public int getRandomNumberFromRange(int Min, int Max) {

            Random rn = new Random();

            int Delta = Max - Min + 1;

            int Offset = rn.nextInt() % Delta;

            int RandVal = Min + Offset;

            if (RandVal == 0)

                  return Min;

            return (RandVal > 0) ? RandVal : (RandVal * -1);

      }

That's it!