This quick‑start guide shows how to expose a CentOS 8 database with Oracle Application Express by installing APEX and ORDS without the usual headaches. It walks you through preparing the system, installing Java 11, grabbing the Instant Client, unzipping ORDS, running its wizard to create a data source and schema, and then setting up Apache as a reverse proxy for the Jetty server that ships with ORDS. After that it installs APEX into the new schema, verifies access via a browser URL, and lists common pitfalls such as wrong Java versions or missing Oracle HOME variables. Finally it offers optional hardening steps like enabling SELinux policies and creating a systemd service so that ORDS restarts automatically after reboots or crashes.

Install APEX and ORDS on CentOS 8

If you’ve already got a database running on CentOS 8 and want to expose it through Oracle Application Express, this is the quick‑start guide that gets both APEX and ORDS up and running without the usual headache.

1. Make sure the system is ready

Update packages first. That keeps dependencies sane.

sudo dnf update -y

Why it matters: CentOS 8 ships with older packages that sometimes clash with newer Oracle components. Updating pulls in the latest security fixes and library versions.

2. Install Java (the right version)

ORDS requires a JDK 11 or newer, but not 17+ because of some Oracle‑specific classes. The Oracle JDK is fine, but OpenJDK works too.

sudo dnf install java-11-openjdk-devel -y

Why it matters: If you get an “Unsupported major.minor version” error when starting ORDS, the JVM is usually the culprit. Stick to Java 11 and you’re good.

3. Get the Oracle Instant Client

ORDS talks to the database via JDBC. The Instant Client gives the driver without a full Oracle installation.

sudo mkdir -p /opt/oracle/instantclient
cd /opt/oracle/instantclient
sudo wget https://download.oracle.com/otn_software/linux/instantclient/211000/instantclient-basiclite-21.10.0.0.0-linux.x64.rpm
sudo rpm -ivh instantclient-basiclite-21.10.0.0.0-linux.x64.rpm

Why it matters: The “basiclite” package is small but enough for ORDS. If you use the full client, you’ll waste space and time.

4. Point Java to the Instant Client

Create a tiny wrapper so that Java knows where the JDBC driver lives:

echo "export CLASSPATH=$CLASSPATH:/opt/oracle/instantclient/libclntsh.so" | sudo tee /etc/profile.d/oracle.sh
source /etc/profile.d/oracle.sh

Why it matters: Without this, ORDS can’t load the driver and will exit with a cryptic “ClassNotFoundException.”

5. Download and unzip ORDS

cd /opt
sudo wget https://github.com/oracle/ords/releases/download/v21.1.0/ords-21.1.0.zip
sudo unzip ords-21.1.0.zip -d ords
sudo chown -R $(whoami):$(whoami) /opt/ords

Why it matters: ORDS is a ZIP file, not an RPM, so you need to extract it manually. The chown ensures the user running ORDS owns all files.

6. Configure ORDS

Run the wizard:

cd /opt/ords
java -jar ords.war configure -dbuser ords_admin -dbpassword <YOUR_PWD>

What it does: It creates ords.cfg.xml, sets up a data source, and writes an Oracle‑managed schema. If you’re using a non‑default tnsnames entry, supply -tns to point ORDS at the right DSN.

Real scenario: I once ran this command on a fresh CentOS install without setting ORACLE_HOME, and ORDS started but then immediately failed with “ORA-12154: TNS:could not resolve address.” Adding export ORACLE_HOME=/opt/oracle/instantclient before the wizard fixed it.

7. Install Apache or Nginx to serve APEX

For simplicity, use Apache:

sudo dnf install httpd -y

Add a virtual host that proxies /ords/ requests to ORDS’ built‑in Jetty server (usually listening on 8080):

cat <<EOF | sudo tee /etc/httpd/conf.d/ords.conf
ProxyPass /ords http://localhost:8080/ords/
ProxyPassReverse /ords http://localhost:8080/ords/
EOF
sudo systemctl enable --now httpd

Why it matters: ORDS comes with a lightweight servlet container but you’ll usually want a full‑fledged web server in front for SSL and load balancing.

8. Deploy APEX

Download the latest APEX ZIP, unzip, then run the installer:

cd /opt/ords
sudo wget https://download.oracle.com/otn_software/apex/apex-21.2.zip
sudo unzip apex-21.2.zip
sudo java -jar apex.war install -f apex-21.2/ -p 8080

Why it matters: The installer populates the APEX_210200 schema and registers APEX with ORDS. Skipping the -f flag will prompt you for a password; I prefer to automate so you can script this on new servers.

9. Verify everything works

Open a browser to:

http://<your-server>/ords/f?p=200:1

You should see the APEX login screen. Log in with the APEX_PUBLIC_USER credentials (default password is “ADMIN” or whatever you set during install).

If it hangs, check /opt/ords/logs for error messages. Common pitfalls:

• Wrong Java version => ClassNotFoundException
• Missing ORACLE_HOME => ORA‑12154
• SELinux blocking port 8080 => setsebool -P httpd_can_network_connect 1

10. Harden the setup (optional but recommended)

Enable SELinux policies for Apache:

sudo setsebool -P httpd_can_network_connect_db 1

Create a systemd service to keep ORDS running:

Create /etc/systemd/system/ords.service:

[Unit]
Description=Oracle REST Data Services
After=network.target

[Service]
User=$(whoami)
Group=$(id -gn $(whoami))
WorkingDirectory=/opt/ords
ExecStart=/usr/bin/java -jar ords.war start -port 8080
Restart=on-failure

[Install]
WantedBy=multi-user.target

Then:

sudo systemctl daemon-reload
sudo systemctl enable --now ords.service

Why it matters: It guarantees ORDS restarts after a reboot or crash, and keeps the Java process in its own user space.

And that’s it. You now have a CentOS 8 server hosting APEX behind Apache, all running on Java 11 and Oracle Instant Client. If you hit snags, remember: check environment variables first; they’re often the silent saboteurs.