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Cássio Freitas

DevOps
Linux | Zabbix
JavaScript | C# | .NET Core
CloudFlare

Brazilian living in Brazil
Only remote work
[email protected]

linkedin.com/in/cassio-freitas
github.com/cassiofreitas/

Portuguese: native
English: B2 level

Profile

I have been working with Linux, open-source and free software since 1993; working with information technology solutions since 1987; and I have been improving my skills to solve problems with technology since 1984.

I am a creative person and I use my knowledge and my abilities to combine technologies to solve problems. If I don't know what to do, I will find a way, to deliver the required solutions. In this profile, on the Achievements (most relevant) topic, I summarized some of my projects.

I have already delivered solutions using Linux [ Slackware and Ubuntu ], OpenLDAP, Squid, Apache, RADIUS, Samba, Captive Portal, NGINX, bash, PHP, Perl, iptables/ipset, pfSense, CloudFlare, Oracle OCI, VMWare and related technologies, providing reliable, stable, and open services, with financial saves. Just as an example, I have already set up gateways, bridges, firewalls, HTTP/HTTPS servers, e-mail servers, and file servers, all of them using open source and free software.

My mindset is to be a lifelong (self) learning ever; to keep an eternal passion for studying, solving problems and learning new skills every day; and my focus is to build systems and solutions that are simple, efficient, robust and compliant.

I believe and have as goals, that technology must be used to provide better quality of life; and innovation, automation and digital transformation must release people from repetitive tasks.

Achievements (most relevants)

Single Sign On deployment

2016 to 2021

Single sign on using Linux for thousands (peak almost 3K) simultaneous users; running for five years with financial savings and stability.

Results and advantages: before this solution, users used to have multiple credentials and no centralized way to change passwords.

Activities and technologies

Activities

Technologies

Problems and alternative solutions analysis

Slackware

Solution blocks design

pfSense

Systems, services and servers configuration

VMWare

Software deployment

OpenLDAP

Systems integration

Apache

Manual configurations testing

Squid

Software, systems and configuration maintenance

RADIUS

Samba

Courier (IMAP/POP3)

Captive Portal

Bash

Perl

Oracle OCI Nginx frontend

2019 to 2021

Implementation of a HTTP/HTTPS frontend with NGINX to protect applications (.NETCore; node js; static content) running in an Ubuntu Linux solution, at Oracle OCI (cloud); protected by CloudFlare WAF; serving hundreds of thousands access by month to educational systems. First version was deployed with Slackware and on premises VMWare virtual machine.

Results and advantages: running for two years with stability, efficiency, and financial savings; high availability provided by Oracle OCI; high security provided by CloudFlare WAF.

Activities and technologies

Activities

Technologies

Researching options and best solutions

Ubuntu

System and operating system installation

Nginx

System configuration

Slackware

Configuration hardening

Oracle OCI

Manual testing the final solution

CloudFlare

Configuration and system Maintenance

VMware

.NET Core (runtime framework)

node.js (server side)

iptables/ipset

Bash

System Administration Task Automation

2006 to 2021

Implementation of several scripts and simple applications using bash, PHP and Perl to automate dozens of manual tasks like add or delete firewalls rules; insert usernames at databases; remove usernames from groups; and to online lock/release internet at labs and so one. They have been running for 15 years without major issues.

Activities and technologies

Activities

Technologies

Problems and solutions analysis

Slackware

Research for alternative solutions

Bash

Designing the code blocks

PHP

Code development

Perl

System and servers configuration

Linux utilities (rsync; ssh; ipset; iptables; scp etc)

Code deployment and manual testings

Code, system and servers maintenance

Captive Portal with Integrated Gateway and Firewall

August 2021 to

Captive Portal Designing (implementation pending), using open source solutions. This project was organized in three phases:

• phase 1: integration with existing Single Sign On solution, for hundreds of users;
• phase 2: integration with iptables/ipset and users groups linking;
• phase 3: web console for administrative tasks;

The main advantages are: portability; completely open source; transparency; stability; simplicity; financial savings.

Activities and technologies

Activities

Technologies

Problem and requirements analysis

Slackware

Research for better alternatives

Apache

Designing the solution and code blocks

Bash

Code development

PHP

System, services and server configuration

CSS

Code and configuration deployment

HTML

Integration with the single sign on solution

Netfilter (iptables and ipset)

Manual testing code and integrations

Code, systems and servers maintenance

Backup and recovery solution

2020 - 2021

Design an implementation of a backup, recovery and test solution, to migrate on premises backup to a cloud storage.

Results and advantages:

• before this improvement, backups used to require dozens of TB storage in local disks, with constant demands of hardware replacement and maintenance and no scalability to provide a constant space requirement growth.
• after, using combined applications with GNU/Linux; Gooogle Drive; and S3 compatible buckets at Oracle OCI; the space availability and scalabililty were attended; no more constants hardware replacements and maintenance; allowing to financial saves with no more hardware acquisition and maintenance and system simplicity and observability.
• Google Drive replacement: in 2021, Google announced that no limits Google Drive would no more be available and this triggered the change we have made to use S3 buckets at Oracle OCI.

Activities and technologies

Activities

Technologies

Problem and requirements analysis

Slackware

Research for better alternatives

Apache

Designing the solution and code blocks

Bash

Code development

PHP

ystem, services and server configuration

rclone

Code and configuration deployment

rsync

Integration with the single sign on solution

Oracle OCI S3

Manual testing code and integrations

Code, systems and servers maintenance

Oracle OCI contracting

CloudFlare DNS and WAF

2021

CloudFlare's WAF and DNS customization to protect all educational and institutional web applications.

Results and advantages:

• before this solution, there were gaps of protection, visibility and logging of web accesses and DNS was requiring better management tools.
• after DNS and WAF provided significant and higher level of security, visibility and stability; after month running, CloudFlare's solution had already blocked thousands of attacks (SQL injection for example) and saved TB of data via cached content; all this results were got using the basic PRO PLAN, for US$ 20,00/month;

Activities and technologies

Activities

Technologies

Problem and requirements analysis

CloudFlare DNS

Research for better alternatives

CloudFlare WAF

System, services and server configuration

CloudFlare Firewall

Manual testing code and integrations

Configuration, systems and servers maintenance

Employment

last 10 years only

Technologies

Most relevant tools I have used in the last 10 years

Other tools and tecnologies I have already used and built solutions with

And some new topics I am learning, to improve my frontend and backend dev skills.

Education