Get Oracle XE-ORDS-APEX Up and Running Quickly with Ansible

Posted on May 8, 2021 by Ajitabh

Oracle APEX is a rapid application development tool and from what I have seen its quite powerful. Clubed together with ORDS, it is a powerful tool to develop enterprise applications which are highly scalable, provided you are willing to spend $$$$ as everything depends on underlying Oracle Database.

For those who want to learn the tool, Oracle XE (Express Edition) can be used as a development environment. Setting up the full stack can be a little bit challenging for developers who wants to stick to building their core strength and not mess with infrastructure deployments etc.

To help here, I wrote this ansible playbook, which will quickly setup the entire stack. Accompanied in the git repository are the Vagrantfile which can quickly setup the DEV environment in a VirtualBox VM. The stack is currently based on CentOS 7.x (and can run in RHEL 7.x as well).

The README file in the git repostory is self explanatory and explains in detail on how to use this playbook to get the stack up and running.

Upcoming Enhancements

I will be making suitable modifications in to make it run on RHEL 8.x and Oracle Linux 8.x. I will also be working on fixing the accompanied packer file which has not been tested thoroughly for building a Docker Image. I plan to get a packer file in place to build a VirtualBox box file, a Digital Ocean droplet image, and a Docker build.

Keep watching the GitHub repository for the changes and do report any issues or feature enhancements. Feel free to submit PRs in case you get to the planned enhancements before me.

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Upgrading Raspbian 8 (Jessie) to Raspbian 9 (Stretch)

Posted on December 25, 2020 by Ajitabh

I decided to upgrade my oldest Raspberry Pi to the latest Raspbian. Since I was two releases behind, I decided to do it step-by-step. Today I updated from 8 – 9. I plan. to perform similar steps to upgrade 9 – 10.

Following are the quick sequence of steps I followed to perform the upgrade. This is a Model B Rev 2 Pi, so was considerably slow to update and took me more than 4 hours to complete.

Step 1 – Prepare The System For Upgrade

Apply the latest updates to the system.

$ sudo apt update && sudo apt upgrade -y && sudo apt-get dist-upgrade -y

Next step is to search for packages which have been only partially installed on the system using dpkg -C command. 

$ sudo dpkg -C

The dpkg may indicate what needs to be done with these. I did not find anything under this category, which was good. In last, I ran apt-mark showhold command to get a list of all packages which have been marked as hold. 

$ sudo apt-mark showhold

While I did not get any packages in this list, but if there are any, we are expected to resolve this before proceedig to step 2.

Stpe 2 – Prepare the APT System for Upgrade

$ sudo sed -i 's/jessie/stretch/g' /etc/apt/sources.list
$ sudo sed -i 's/jessie/stretch/g' /etc/apt/sources.list.d/raspi.list
$ echo 'deb http://archive.raspberrypi.org/debian/ stretch main' >> /etc/apt/sources.list

I am updating only the two files but if your system has any other source files, then you need to update them appropriately as well. A list of such files can be found using – grep -lnr jessie /etc/apt

In addition to this I also removed the package apt-listchange which displays what changed in the new version of the Debian package as compared to the version currently installed on the system. This is expected to speed-up the entire process. This is not mandatory, so you can skip it.

# optional step
$ sudo apt-get remove apt-listchange

Step 3 – Perform The Upgrade and Cleanup

As a last step initiate the upgrade process. This is the time where you can just leave the system for few hours. 

$ sudo apt update && sudo apt upgrade -y && sudo apt-get dist-upgrade -y

I faced issues with chromium-browser and at the last command (dist-upgrade), the dpkg bailed out with a message indicating archive corruption of chromium-browser package. Since I am at Run Level 3, and do not need chromium on the headless pi, I decided to remove the following three packages. In any case in the absence of chromium, the debian system will automatically use update-alternatives and choose epiphany-browser to satisfy gnome-www-browser requirement.

$ sudo apt-get remove chromium-browser chromium-browser-l10n rpi-chromium-mods

After removing the chromium browser, I did another round of update, upgrade and dist-upgrade, just to make sure before initiating the cleanup as below –

$ sudo apt-get autoremove -y && sudo apt-get autoclean

The new OS version can be verified by

$ cat /etc/debian_version;cat /etc/os-release

I also took this opportunity to update the firmware of the raspberry pi by running the following command. Please note this step is absolutely optional and it is recomended also that do not perform this unless you know what you are doing or you are being asked by a support person.

$ sudo rpi-update

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Raspberry Pi – rsyslog fixes on Raspbian 8 (Jessie)

Posted on December 25, 2020 by Ajitabh

One of my Raspberry Pi (Raspberry Pi Model B Rev 2) is running quite old versio of Rasbian – although fully updated and patched. Today while checking the syslog on my raspberry pi, I noticed the following error which was very frequently – almost every minute and thus was filling up the syslog. 

Dec 24 20:59:35 rads rsyslogd-2007: action 'action 17' suspended, next retry is Thu Dec 24 21:01:05 2020 [try http://www.rsyslog.com/e/2007 ]

Thanks to logrotate I was not in an immediate need for action, but still I thought it will be better to fix this – atleast that will reduce the write and increase life of my SD Card.

The URL at the end of the message was very helpful. According to the specified URL this message simply means that rsyslog.conf contains the instruction to write to the xconsole pipe, but this pipe is never read. on editing the /etc/rsyslog file, the following section can be commented out or removed completely. 

daemon.*;mail.*;\        news.err;\        *.=debug;*.=info;\        *.=notice;*.=warn       |/dev/xconsole

A simple systemctl restart rsyslog after that will fix the issue.

I did not see this issue on my other Raspberry Pi which runs Raspbian based on Debian Buster (Debian 10). I checked the /etc/rsyslog.conf on that and could not find the offending lines there. So my understanding is that this issue is with Raspbian based on Jessie.

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Using Wrap Utility to Hide the SQL Code in Oracle

Posted on July 15, 2019 by Ajitabh

At times we may need to encrypt sensitive information in certain columns in Oracle Database. Oracle provides a DBMS_CRYPTO package for the purpose. More details about this package can be found in Oracle Documentation here.

The approach I followed is as follows –

  • Create a custom package using features provided in DBMS_CRYPTO, which will consists for functions to encrypt / decrypt varchar and blob type columns.
  • Use this package to encrypt / decrypt the data in the fields.

For a reference implementation of such a code, you can refer to the Oracle Documentation mentioned above.

One key aspect is the use of a ‘Key’ in the encryption logic. In the sample code given on the documentation, a random key has been chosen. This random key is fine as long as you do not recompile the package. If the package is recompiled then the key changes and hence invalidates all the encrypted data which can not be decrypted in the absence of the old key.

If we keep the key as fixed, then anyone looking at the source code of the package can see the key and thus potentially compromising on the security aspects.

To resolve this, fortunately Oracle provides a wrap utility to hide the source code.

$ wrap iname=enc_dec.sql oname=enc_dec.sql.wrp

SQL> @enc_dec.sql.wrp;

Now anyone looking at the source code of the package will find gibberish understood by Oracle only. However, the original source with the key has to be kept safe, just incase you need it back again.

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Apt Pinning in Raspbian

Posted on June 17, 2018 by Ajitabh

Quite sometime back I wrote a blog entry on apt-pinning to mix multiple repositories in debian and prioritize them. Recently, I felt the need to do the same on my raspberry pi.

I use rsnapshot to backup remote systems. Rsnapshot has an associated perl script which is meant to send beautiful reports via email at the end of the backup. The script in the version which came with raspbian was broken (1.3.1-4+deb8u1) and I needed 1.4.2-1, which is available in Debian Stretch.

Following my earlier post, I performed the following steps to perform the installation of the required version without impacting the rest of the system. As you can see that the priority of Jessie is higher than that of Stretch, which will ensure that the system does not get messed up when you do an upgrade.

# Create the preferences file for jessie and stretch as shown below
$ sudo vi /etc/apt/preferences.d/jessie.pref
Package: *
Pin: release n=jessie
Pin-Priority: 900

$ sudo vi /etc/apt/preferences.d/stretch.pref
Package: *
Pin: release a=stretch
Pin-Priority: 750

# Define the package sources for both jessie and stretch
$ sudo vi /etc/apt/sources.list.d/jessie.list
deb http://mirrordirector.raspbian.org/raspbian/ jessie main contrib non-free rpi

$ sudo vi /etc/apt/sources.list.d/stretch.list
deb http://mirrordirector.raspbian.org/raspbian/ stretch main contrib non-free rpi

# Refresh the cache and sources list
$ sudo apt-get update

# Install the desired package by specifying the repository from which 
# it has to be installed
$ sudo apt-get install rsnapshot -t stretch

Please be careful before performing these steps in a production system.

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