Java Object Oriented Programming Introduction (12 Minutes)

In this video we introduce Java object-oriented programming (12 minutes).

Subscribe: https://www.youtube.com/channel/UCZUyPT9DkJWmS_DzdOi7RIA

#java #programming

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How to Find Ulimit For user on Linux

How can I find the correct ulimit values for a user account or process on Linux systems?

For proper operation, we must ensure that the correct ulimit values set after installing various software. The Linux system provides means of restricting the number of resources that can be used. Limits set for each Linux user account. However, system limits are applied separately to each process that is running for that user too. For example, if certain thresholds are too low, the system might not be able to server web pages using Nginx/Apache or PHP/Python app. System resource limits viewed or set with the NA command. Let us see how to use the ulimit that provides control over the resources available to the shell and processes.

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MEAN Stack Tutorial MongoDB ExpressJS AngularJS NodeJS

We are going to build a full stack Todo App using the MEAN (MongoDB, ExpressJS, AngularJS and NodeJS). This is the last part of three-post series tutorial.

MEAN Stack tutorial series:

AngularJS tutorial for beginners (Part I)
Creating RESTful APIs with NodeJS and MongoDB Tutorial (Part II)
MEAN Stack Tutorial: MongoDB, ExpressJS, AngularJS and NodeJS (Part III) 👈 you are here
Before completing the app, let’s cover some background about the this stack. If you rather jump to the hands-on part click here to get started.

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systemctl List All Failed Units/Services on Linux

Is there is a command to print list all failed units or services when using systemd on Linux? Can you tell me the systemctl command to list all failed services on Linux?

This quick tutorial explains how to find/list all failed systemd services/units on Linux operating systems using the systemctl command.

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CentOS Linux 8.2 Released and Here is How to Upgrade it

CentOS Linux 8.2 (2004) released. It is a Linux distribution derived from RHEL (Red Hat Enterprise Linux) 8.2 source code. CentOS was created when Red Hat stopped providing RHEL free. CentOS 8.2 gives complete control of its open-source software packages and is fully customized for research needs or for running a high-performance website without the need for license fees. Let us see what’s new in CentOS 8.2 (2004) and how to upgrade existing CentOS 8.1.1199 server to 8.2.2004 using the command line.

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FreeBSD s3cmd failed [SSL CERTIFICATE_VERIFY_FAILED]

When I install s3cmd package on my FreeBSD system and try to use the s3cmd command I get the following error:

_ERROR: Test failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (ssl.c:1091)

How do I fix this problem on FreeBSD Unix system?

Amazon Simple Storage Service (s3 ) is object storage through a web service interface or API. You can store all sorts of files. FreeBSD is free and open-source operating systems. s3cmd is a command-line utility for the Unix-like system to upload, download files to AWS S3 service from the command line.

ERROR: Test failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed error and solution

This error indicates that you don’t have packages correctly installed, especially SSL certificates. Let us see how to fix this problem and install s3cmd correctly on FreeBSD to get rid of the problem.

How to install s3cmd on FreeBSD

Search for s3cmd package:

$ pkg search s3cmd

Execute the following command and make sure you install Python 3.x package as Python 2 will be removed after 2020:

$ sudo pkg install py37-s3cmd-2.1.0

Updating FreeBSD repository catalogue...
FreeBSD repository is up to date.
All repositories are up to date.
Checking integrity... done (0 conflicting)
The following 8 package(s) will be affected (of 0 checked):

New packages to be INSTALLED:
	libffi: 3.2.1_3
	py37-dateutil: 2.8.1
	py37-magic: 5.38
	py37-s3cmd: 2.1.0
	py37-setuptools: 44.0.0
	py37-six: 1.14.0
	python37: 3.7.8
	readline: 8.0.4

Number of packages to be installed: 8

The process will require 118 MiB more space.

Proceed with this action? [y/N]: y
[rsnapshot] [1/8] Installing readline-8.0.4...
[rsnapshot] [1/8] Extracting readline-8.0.4: 100%
[rsnapshot] [2/8] Installing libffi-3.2.1_3...
....
..
[rsnapshot] [8/8] Extracting py37-s3cmd-2.1.0: 100%
=====
Message from python37-3.7.8:

--
Note that some standard Python modules are provided as separate ports
as they require additional dependencies. They are available as:

py37-gdbm       databases/py-gdbm@py37
py37-sqlite3    databases/py-sqlite3@py37
py37-tkinter    x11-toolkits/py-tkinter@py37

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