Installing Oracle XE on CentOS

Another Cricket World Cup is underway. England are fulfilling their traditional role of making all of the other teams look like world beaters.
To take my mind off this excruciating spectacle, I’ll concentrate this week on installing Oracle XE 11g on CentOS 7.

Before I get into the nuts and bolts of the installation…

Flavours of Linux

Whilst there are many Linux Distros out there, they all share the same common Linux Kernel. Within this there are a few Distros upon which most others are based.
Debian provides the basis for Ubuntu and Mint among others.
It uses the .deb package format.

Red Hat Linux in contrast uses the RPM file format for it’s packages. Red Hat is the basis for Distros such as Fedora, CentOS…and Oracle Linux.

For this reason, the Oracle Express Edition Linux version is packaged using rpm.
Whilst it is possible to deploy it to a Debian based Distro – instructions for which are available here, deploying on CentOS is rather more straightforward.
More straightforward, but not entirely so, as we will discover shortly…

Getting Oracle Express Edition 11G

Open your web browser and head over the the Oracle Express Edition download page.

You’ll need to register for an account if you don’t already have one but it is free.

The file you need to download is listed under :

Oracle Express Edition 11g Release 2 for Linux x64.

NOTE XE 11G only comes in the 64-bit variety for Linux. If you’re running a 32-bit version of your Distro, then you’re out of luck as far as 11G is concerned.

If you’re not sure whether you’re on 32-bit or 64-bit, the following command will help you :

uname -i

If this returns x86_64 then your OS is 64-bit.

Installing XE

You should now have downloaded the zipped rpm file which will look something like this :

cd $HOME/Downloads
ls -l
-rwxrwx---. 1 mike mike 315891481 Dec 16 20:21 oracle-xe-11.2.0-1.0.x86_64.rpm.zip

The next step is to uncompress…

 unzip oracle-xe-11.2.0-1.0.x86_64.rpm.zip

When you run this, the output will look like this :

   creating: Disk1/
   creating: Disk1/upgrade/
  inflating: Disk1/upgrade/gen_inst.sql  
   creating: Disk1/response/
  inflating: Disk1/response/xe.rsp   
  inflating: Disk1/oracle-xe-11.2.0-1.0.x86_64.rpm 

You now need to switch to the newly created Disk1 directory and become root…

cd Disk1
su

…and then install the package…

rpm -ivh oracle-xe-11.2.0-1.0.x86_64.rpm

If all goes well you should see…

Preparing...                          ################################# [100%]
Updating / installing...
   1:oracle-xe-11.2.0-1.0             ################################# [100%]
Executing post-install steps...
You must run '/etc/init.d/oracle-xe configure' as the root user to configure the database.

Configuring XE

The configuration will be prompt you for

1. the APEX http port (8080 by default)
2. the database (TNS) listener port (1521 by default)
3. A single password to be assigned to the database SYS and SYSTEM users
4. whether you want the database to start automatically when the system starts (Yes by default)

Unless you have other software, or Oracle Instances, running elsewhere, the defaults should be fine.

Here we go then, still as root, run :

/etc/init.d/oracle-xe configure

The output, complete with the prompts will be something like :

Oracle Database 11g Express Edition Configuration
-------------------------------------------------
This will configure on-boot properties of Oracle Database 11g Express 
Edition.  The following questions will determine whether the database should 
be starting upon system boot, the ports it will use, and the passwords that 
will be used for database accounts.  Press <Enter> to accept the defaults. 
Ctrl-C will abort.

Specify the HTTP port that will be used for Oracle Application Express [8080]:8081

Specify a port that will be used for the database listener [1521]:1525

Specify a password to be used for database accounts.  Note that the same
password will be used for SYS and SYSTEM.  Oracle recommends the use of 
different passwords for each database account.  This can be done after 
initial configuration:
Confirm the password:

Do you want Oracle Database 11g Express Edition to be started on boot (y/n) [y]:y

Starting Oracle Net Listener...Done
Configuring database...Done
Starting Oracle Database 11g Express Edition instance...Done
Installation completed successfully.

Congratulations, you now have a running database. The first thing to do with it, however, is to shut it down.
In fact, we need to do a re-start so that the menu items that have been added as part of the installation are visible.
So, re-boot.

NOTE – from this point on you can stop being root (although you may need to sudo occasionally).

Once the system comes back, you will see the new Menu icons in the Applications menu under others :

Just to confirm that your database is up and running, you can select the Run SQL Command Line option from this menu
and run the following :

conn system/pwd
select sysdate from dual
/

This should return the current date.

Sorting out the Environment Variables

In the normal run of things, this is the one fiddly bit. There is a bug in one of the scripts Oracle uses to set the environment variables which may cause issues.

To start with, let’s have a look at the main environment script…

cat /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh

This script is as follows :

export ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe
export ORACLE_SID=XE
export NLS_LANG=`$ORACLE_HOME/bin/nls_lang.sh`
export ORACLE_BASE=/u01/app/oracle
export PATH=$ORACLE_HOME/bin:$PATH

There is a bug in the nls_lang.sh that is called from here. If you’re NLS_LANG value contains a space, then it will not be configured correctly. A full list of the affected NLS_LANG values is available on the Oracle XE Installation Guide for Debian based systems I mentioned earlier.

The easiest way to fix this is to just edit the script :

sudo gedit /u01/app/oracle/product/11.2.0/xe/bin/nls_lang.sh

Right at the bottom of the script where it says :

# construct the NLS_LANG
#
NLS_LANG=${nlslang}.${charset}

echo $NLS_LANG

…amend it so that the $NLS_LANG value is quoted :

# construct the NLS_LANG
#
NLS_LANG="${nlslang}.${charset}"

echo $NLS_LANG

To test the change and make sure everything is now working properly…

cd /u01/app/oracle/product/11.2.0/xe/bin

. ./oracle_env.sh
echo $ORACLE_HOME
echo $ORACLE_SID
echo $NLS_LANG
echo $PATH

You should now see the following environment variable settings :

echo $ORACLE_HOME
/u01/app/oracle/product/11.2.0/xe
echo $ORACLE_SID
XE
echo $NLS_LANG
ENGLISH_UNITED KINGDOM.AL32UTF8
$PATH
/u01/app/oracle/product/11.2.0/xe/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/mike/.local/bin:/home/mike/bin

NOTE – the $NLS_LANG should have a setting appropriate for your system (in my case ENGLISH_UNITED KINGDOM.AL32UTF8).

The Oracle bin directory is now at the start of $PATH.

Next, we need to ensure that these environment variables are set for all sessions. This can be done by running …

sudo cp /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh /etc/profile.d/.

To check this, you can start a new terminal session and echo the environment variables to make sure they have been set.

Getting the Menu Items to Work

To do this, you simply need to make sure that the oracle user, as well as your own user, is a member of the dba group :

sudo usermod -a -G dba oracle
sudo usermod -a -G dba mike

To check :

sudo grep dba /etc/group
dba:x:1001:oracle,mike
$

The menu items for starting up and shutting down the database etc. should now work.

Enabling the Getting Started Desktop Icon

The final touch. The installation creates a Getting Started icon on the desktop which is designed to open the Database Home Page of the APEX application that comes with XE.

In order to make it work as desired, you simply need to right-click the icon and select Properties.
In the Permissions Tab check the box to “Allow executing file as program”.
Close the window.

You will notice that the icon has transformed into the familiar Oracle beehive and is now called
Get Started With Oracle Database 11g Express Edition.

Clicking on it now will reward you with …

All-in-all then, this installation is reasonably painless when compared with doing the same thing on a Debian system.
I wish the same could be said of following the England Cricket Team.