A Technical I.T./DevOps Blog
Problem scenario
You want to test connectivity to a database. But you do not know anything about the database beyond its connection information. What SQL statement is universal and guaranteed to work?
Solution
show databases;
…
Continue reading “What is a SQL Statement That Will Work for Any MySQL Database?”
Problem scenario
You have a role that you want to execute a Lambda function. What do you do?
Solution
1. Log into the AWS console.
2. Go to IAM -Roles
3. Click on the role you want to change.
4. Click on “Attach policies”
5. In the “Filter policies” field search for “lambda” with no quotes
6.
…
Continue reading “How Do You Grant a Role The Ability to Run a Lambda Function?”
Question
What SQL database underlies Elastic Search?
Answer
There is no relational database for Elastic Search.
Elastic Search will have a cluster that is composed of nodes. Nodes are composed of indexes. Indexes are supported by shards. Shards have primary and replica copies. The replica copies vary. The shards are essentially Lucene indexes (according to this site).
…
Question
In the context of Linux, what is a system call?
Answer
A system call is a special OS function with a human-readable name (according to page 11 of Sobell’s A Practical Guide to Fedora and RedHat Enterprise Linux). Such a function allows for programs to interact with the kernel (according to page 11 of Sobell’s A Practical Guide to Fedora and RedHat Enterprise Linux).
…
Continue reading “In the Context of Linux, what is a System Call?”
Problem scenarios (one or both of the following are happening)
#1 You are getting “botocore.exceptions.NoRegionError: You must specify a region” when you run a Python program (that involves boto and AWS).
#2 You are trying to create a session with a Python/boto program. You are printing out the Session information in your Python program using boto but you see this:
Session(region_name=None)
What should you do?
…
Continue reading “How Do You Troubleshoot the boto Message “NoRegionError”?”
Problem scenario
You want to use the rdf4j (Resource Description Framework for Java). You want to install the rdf4j server and workbench. You are using Debian 9 Linux. What should you do?
Solution
Prerequisites
i. We recommend having a 30 GB of hard disk free.
ii. We recommend having 5.75 GB of RAM (it can be a combination of RAM and swap space).
…
Continue reading “How Do You Install and Configure the rdf4j Server and Workbench GUI?”
Problem scenario
You run a Python program. A value of a variable is printing “function at” with a hexadecimal. How can the variable be the intended value of the function and not this meta data of the Python interpreter or just-in-time compiler?
Solution
Use “()” at the end of the function invocation. This syntax is necessary. Here is an example that will cause the problem:
def cool():
a = “foobar”
return a
q = cool
print(q)
Here is an example that will not cause the problem:
def cool():
a = “foobar”
return a
q = cool()
print(q) …
Continue reading “Why Does Your Python Program Return “function at” with a Hexadecimal?”
Problem scenario
You want to use the same command for encryption and compression. You want the compression to be high (for maximum data density for backups and storage purposes). You can install a new package. What should you do?
Solution
Use 7zip.
Prerequisite
Try whereis 7z to see if 7zip is installed. If it is not,
…
Problem scenario
You want to create a Windows server in Google Cloud Platform. How do you do this?
Solution
1. Log into Google Cloud Platform.
2. Click the hamburger icon in the upper left hand corner (the icon with three horizontal bars stacked onto each other).
3. Go to Compute Engine -VM Instances
4. Click “Create Instance”
5.
…
Continue reading “How Do You Create a Windows VM in Google Cloud Platform with the Console?”
Problem scenario
HAProxy can be a load balancer or reverse proxy server. You want to know if HAProxy is running or not from the back-end of the Linux server. How do you determine HAProxy’s status?
Solution
Run this command: sudo /etc/init.d/haproxy status
…
Continue reading “How Do You Determine if HAProxy is up and Running or Not?”