how to make firefox work in SSO


You can configure Firefox to use Kerberos for Single Sign-on. In order for this functionality to work correctly, you need to configure your web browser to send your Kerberos credentials to the appropriate KDC.The following section describes the configuration changes and other requirements to achieve this.
  1. In the address bar of Firefox, type about:config to display the list of current configuration options.
  2. In the Filter field, type negotiate to restrict the list of options.
  3. Double-click the network.negotiate-auth.trusted-uris entry to display the Enter string value dialog box.
  4. Enter the name of the domain against which you want to authenticate, for example,
  5. Repeat the above procedure for the network.negotiate-auth.delegation-uris entry, using the same domain.


    You can leave this value blank, as it allows Kerberos ticket passing, which is not required.
    If you do not see these two configuration options listed, your version of Firefox may be too old to support Negotiate authentication, and you should consider upgrading.

Configuring Firefox for SSO with Kerberos

Figure 48.6. Configuring Firefox for SSO with Kerberos

You now need to ensure that you have Kerberos tickets. In a command shell, type kinit to retrieve Kerberos tickets. To display the list of available tickets, type klist. The following shows an example output from these commands:

SQL Query to concatenate column values from multiple rows in Oracle


Table A


Table B

PID   SEQ    Desc

A     1      Have
A     2      a nice
A     3      day.
B     1      Nice Work.
C     1      Yes
C     2      we can 
C     3      do 
C     4      this work!

Output of the SQL should be –

PID   Desc
A     Have a nice day.
B     Nice Work.
C     Yes we can do this work!


Then join to A to pick out the pids you want.

auto start/stop Oracle on linux


The following sample is for Oracle 12c:

The following represents the Oracle recommended method for automating database startup and shutdown of Oracle 9i instances on Linux, but it works equally well for Oracle 10g, 11G and 12c also. It can be used on any RHEL-style distribution, including Oracle Linux, up to an including RHEL7.

Once the instance is created, edit the “/etc/oratab” file setting the restart flag for each instance to ‘Y’.


Create a file called “/etc/init.d/dbora” as the root user, containing the following code.

# chkconfig: 345 99 10
# description: Oracle auto start-stop script.
# Set ORA_HOME to be equivalent to the $ORACLE_HOME
# from which you wish to execute dbstart and dbshut;
# Set ORA_OWNER to the user id of the owner of the 
# Oracle database in ORA_HOME.

export ORACLE_UNQNAME=db12c

if [ ! -f $ORA_HOME/bin/dbstart ]
    echo "Oracle startup: cannot start"

case "$1" in
        # Start the Oracle databases:
        # The following command assumes that the oracle login 
        # will not prompt the user for any values
        # Remove "&" if you don't want startup as a background process.
        su $ORA_OWNER -c "$ORA_HOME/bin/dbstart $ORA_HOME" &
        touch /var/lock/subsys/dbora
        # Stop the Oracle databases:
        # The following command assumes that the oracle login 
        # will not prompt the user for any values
        su $ORA_OWNER -c "$ORA_HOME/bin/dbshut $ORA_HOME"
        rm -f /var/lock/subsys/dbora

Use the chmod command to set the privileges to 750.

chmod 750 /etc/init.d/dbora

Associate the “dbora” service with the appropriate run levels and set it to auto-start using the following command.

chkconfig --add dbora

The relevant instances should now startup/shutdown automatically at system startup/shutdown.

set default jdk using alternatives


⁠C.4.  Setting the default JDK with the /usr/sbin/alternatives Utility

/usr/sbin/alternatives is a tool for managing different software packages that provide the same functionality.Red Hat Enterprise Linux uses /usr/sbin/alternatives to ensure that only one Java Development Kit is set as the system default at one time.


Installing a Java Development Kit from the Red Hat Network will normally result in an automatically configured system. However, if multiple JDKs are installed, it is possible that /usr/sbin/alternativesmay contain conflicting configurations. Refer to Procedure C.4, “ Using /usr/sbin/alternatives to Set the Default JDK ” for syntax of the /usr/sbin/alternatives command.

Procedure C.4.  Using /usr/sbin/alternatives to Set the Default JDK

  1. Become the root user.

    /usr/sbin/alternatives needs to be run with root privileges. Use the su command or other mechanism to gain these privileges.
  2. Set java.

    Input this command: /usr/sbin/alternatives --config java
    Next, follow the on-screen directions to ensure that the correct version of java is selected. Table C.1, “javaalternative commands” shows the relevant command settings for each of the different JDKs.

    Table C.1. java alternative commands

    JDK alternative command
    OpenJDK 1.6 /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
    Sun Microsystems JDK 1.6 /usr/lib/jvm/jre-1.6.0-sun/bin/java
  3. Set javac.

    Enter this command: /usr/sbin/alternatives --config javac
    Follow the on-screen directions to ensure that the correct version of javac is selected. Table C.2, “javacalternative commands” shows the appropriate command settings for the different JDKs.

    Table C.2. javac alternative commands

    JDK alternative command
    OpenJDK 1.6 /usr/lib/jvm/java-1.6.0-openjdk/bin/javac
    Sun Microsystems JDK 1.6 /usr/lib/jvm/java-1.6.0-sun/bin/javac
  4. Extra Step: Set java_sdk_1.6.0.

    The Sun Microsystems JDK 1.6 requires an additional command be run:
    /usr/sbin/alternatives --config java_sdk_1.6.0
    Follow the on-screen directions to ensure that the correct java_sdk is selected. It is /usr/lib/jvm/java-1.6.0-sun.

create the number of open file descriptors for oralce installation


To Increase the File Descriptor Limit (Linux)

Display the current hard limit of your machine.
The hard limit is the maximum server limit that can be set without tuning the kernel parameters in proc file system.

$ ulimit -aH
core file size (blocks) unlimited
data seg size (kbytes) unlimited
file size (blocks) unlimited
max locked memory (kbytes) unlimited
max memory size (kbytes) unlimited
open files 1024
pipe size (512 bytes) 8
stack size (kbytes) unlimited
cpu time (seconds) unlimited
max user processes 4094
virtual memory (kbytes) unlimited
Edit the /etc/security/limits.conf and add the lines:
* soft nofile 1024
* hard nofile 65535
Edit the /etc/pam.d/login by adding the line:
session required /lib/security/
Use the system file limit to increase the file descriptor limit to 65535.
The system file limit is set in /proc/sys/fs/file-max .

echo 65535 > /proc/sys/fs/file-max
Use the ulimit command to set the file descriptor limit to the hard limit specified in /etc/security/limits.conf.
ulimit -n unlimited
Restart your system.

How to enable VMWare internet access

Lot of times when you just completed installation of an linux OS in a VM, you will find that you cannot access internet. There are two scenarios:

  1. The host machine doesn’t need a proxy. In this way, please check if the network item on the upper right corner of VM is enabled. If not, enabling it should solve this issue.
  2. The host machine is behind a proxy. In this scenario, you need to install cntlm. Do the usual steps of cntlm configuration and set up http_proxy environment.
    To set up http_proxy to all users, edit file /etc/profile to add line:
    export http_proxy=http://<hostname>:<portnumber>/, then try the following command to verify if it is successful:
    wget If the page is successfully downloaded then congratulations; otherwise check your cntlm.conf file to see if the configuration is correct.