(bash): The most useless commands (9)

After talking about
  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
  7. rig
here another pretty useless command:

$ pi 10
       The  pi  command  prints  100 decimal digits of Archimedes' constant pi or a number of
       digits specified by an integer parameter on the command line.

Installation of Rundeck with the Ansible plugin on Centos 7

This post shows you how to install Rundeck with the Ansible plugin on Centos 7. The installation is done with nginx as the web server and using SSL with a self signed certificate. Please read the Ansible installation script, and modify anything that should be different for your situation. You will be amazed how well readable the installation script is!

Rundeck is a web based user interface that allows you to run commands against a (more...)

How to exit of ed in SQL*Plus

I from time to time get stuck in ‘ed‘ on SQL*Plus because the editor not defined like this:

SQL> select * from duall;
select * from duall
ERROR at line 1:
ORA-00942: table or view does not exist

SQL> ed
Wrote file afiedt.buf

The Ctrl-C and Ctrl-Z, wouldn’t get you out.

The solution is simple, type ‘q‘ and press ‘Enter‘, then set editor using (more...)

Installation overview of node_exporter, prometheus and grafana

Prometheus is an open source systems monitoring and alerting toolkit originally build at Soundcloud. This blogpost shows how to install the needed components to do visualisation of linux system statistics via Grafana.

The setup consists of 3 components:
node_exporter, an exporter of system and hardware metrics.
prometheus, a metric collection and persistence layer.
grafana, the visualisation layer.

1. Preparation
The needed components are installed in the home directory of (more...)

Linux memory usage

One of the principal important configuration settings for running an Oracle database is making appropriate use of memory. Sizing the memory regions too small leads to increased IO, sizing the memory regions too big leads to inefficient use of memory and an increase in memory latency most notably because of swapping.

On Linux, there is a fair amount of memory information available, however it is not obvious how to use that information, which frequently leads (more...)

12.2 New Feature: the FLEX ASM disk group part 3

In the previous 2 parts of this mini series I introduced the Flex ASM disk group and two related concepts, the Quota Group and File Group. In what should have become the final part (but isn’t) I am interested in checking whether quotas are enforced.

(Un)fortunately I have uncovered a few more things that are worth investigating and blogging about, which is why a) this isn’t the last post and b) it got a bit (more...)

(bash): The most useless commands (8)

After talking about

  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
 i found another funny command:
Its manpage tells the following:
       Rig  is a utility that will piece together a random first name, last name, street num‐
       ber and address, along with a geographically consistant (ie, they all match  the  same
       area) city, state, ZIP code, and area code.

       It is suitable for such applications as feeding the NY times registration (more...)

Bash: enabling Eclipse for Bash Programming | Plugin basheclipse (debugging) part 1

In my last posting i showed how to install the plugin shelled and its configuration options.

Now the next step is to install basheclipse, which enables eclipse in conjunction with shelled to debug bash scripts.

Step 1: Download basheclipse

Step 2: Do not copy the jar file to the plugins directory if you are using Eclipse Neon. Copy them to the dropins directory.

Step 3: Restart eclipse (and wait. I had to wait nearly 5 (more...)

12.2 New Feature: the FLEX ASM disk group part 2

In the first part of this series I explained the basics and some potential motivation behind the use of ASM Flex disk groups. In this part I would like to complete the description of new concepts.

New Concepts related to FLEX ASM Disk Groups

With the Flex disk group mounted, the next steps are to create a few new entities. First, I want to create a Quota Group. The Quota Group – as the name (more...)

Bash: enabling Eclipse for Bash Programming | Plugin Shelled (shell editor)

After writing several posts about useless shell commands i tried to enable Eclipse for working with the bourne again shell.

First step is to get a plugin for syntax highlighting. The plugin shelled
is very easy to find. Just download the zip

and in Eclipse go to "help --> install new software".
There you have to add the archive:
And all other clicks are straight forward:

After the installation of the plugin you (more...)

Postgresql block internals, part 3

This is the third part in a series of blogposts about how postgresql manages data in its blocks (called ‘pages’ in postgres speak). If you found this post and did not read the previous ones, it might be beneficial to read block internals (part 1) and block internals, part 2 first. In these blogposts I’ve shown how heap and index pages look like, and how these can be investigated, including looking at the raw block (more...)

12.2 New Feature: the FLEX ASM disk group part 1

I knew about the 12.2 FLEX ASM disk group type from other presenters but until now – when researching the feature for the upcoming DOAG HA Day – I haven’t been able to appreciate how cool this is. And I really think it is pretty cool and worth sharing! There is a lot to be said about the feature and these tests, which is why I am splitting it into multiple parts.

Please be (more...)

Postgresql block internals, part 2

This is the second part of a blogpost about Postgresql database block internals. If you found this blogpost, and are interested in getting started with it, please read the first part, and then continue with this post.
I am doing the investigations on Oracle Linux 7u3 with postgres 9.6 (both the latest versions when this blogpost was written).

In the first part I talked about the pageinspect extension, and investigated the page header (more...)

Postgresql block internals

This blogpost is the result of me looking into how postgres works, and specifically the database blocks. The inspiration and essence of this blogpost comes from two blogs from Jeremiah Peschka: https://facility9.com/2011/03/postgresql-row-storage-fundamentals/ and https://facility9.com/2011/04/postgresql-update-internals/
I am using Oracle Linux 7u3 and postgres 9.6 (current versions when this blogpost was written).

Postgres is already installed, and a database cluster is already running. Let’s create a database ‘test’ for the sake of our (more...)

(bash): The most useless commands (7)

After talking about
  1. rev
  2. sl
  3. cowsay
  4. cmatrix
here another pretty useless command:
Today with every smartphone having its own calendar app or every e-mail program with integrated time planning function this command is no more needed. The manpage says:
     cal, ncal — displays a calendar and the date of Easter
And here we go:
$ cal 2000

Installing App Designer on Ubuntu

It’s been a while since I have tried to install Application Designer directly on my Linux host. In fact, the last time I tried was many tools versions ago. Since I’ve been playing with a PUM again, it’s time to give it another try.

Here’s my notes:

Installing Wine

I figured that my best chance at getting App Designer to work was to use the latest version of Wine. So, I used the repository to (more...)

(bash): The most useless commands (6)

After talking about
  1. rev
  2. sl
  3. cowsay
 i found another funny command:
The manpage says:
       CMatrix - simulates the display from "The Matrix"
and it is true:

(bash): The most useless commands (5)

In a comment Albert Godfrind pointed out, that the commands i was talking about like
  1. rev
  2. sl
  3. cowsay
are not really bash commands (in a way that they will be installed within the installation of the bash shell). They are commands, which can be used from on every shell. So my headline is a little bit missleading - thanks for this notice.

Just for clarification here a list with all bash builtin commands:

JDBC, Linux and Entropy

Some troubles — especially those happening only sporadically — are not so easy to shoot and call for a deeper understanding of the matter. In the following real-world example this means: SQL*Net Tracing and some knowledge about the inner workings of the server’s operating system, particularly random number generation. This case was suited well to demonstrate an approach to trouble-shoot […]

Oracle Linux: Clean Yum dbcache

These weeks we provide a course on Weblogic 11g and 12c Basic and Advanced Administration and Tuning & Troubleshooting. We use an Oracle Linux 6 VM with a Database and Weblogic 11g and 12c.

We got some complaints (issued in a friendly way, by the way) from the attendees that a filesystem of the VM got filled up.

One of the attendees found out that the following folder containt some very large files:

-rw-r--r--. (more...)