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5. Linux Basic Commands

5.7 Package Management: yum and apt

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Also in the AWS course: this lesson is the same as 3.7 Package managers in the AWS course, which is the main version of this page.

Package manager mhanje mobile madla Play Store – tumhi naav sangta, to trusted repository madhun software aani tyache dependencies aanto.

Task Ubuntu / Debian (apt) Amazon Linux 2023, Amazon Linux 2, CentOS Stream 9 (yum)
Refresh package list sudo apt update (automatic) sudo yum makecache
Upgrade all sudo apt upgrade -​y sudo yum update -y
Install sudo apt install -​y nginx sudo yum install -​y nginx*
Remove sudo apt remove nginx (purge removes config too) sudo yum remove nginx
Search apt search php yum search php
Info apt show nginx yum info nginx
List installed apt list --​installed yum list installed
Which package gives a file dpkg -​S /​usr/​sbin/​nginx yum provides /​usr/​sbin/​nginx
Clean cache sudo apt autoremove && sudo apt clean sudo yum clean all
Package file format .deb (dpkg -i) .rpm (rpm -i)

* On Amazon Linux 2, some packages come from amazon-linux-extras (e.g. sudo amazon-linux-extras install nginx1). Amazon Linux 2023 has no amazon-linux-extras; everything is in the regular repositories.

Why this matters for security

Unpatched packages are one of the most common ways in. sudo yum update -y / sudo apt upgrade -y fixes known vulnerabilities (कमकुवत जागा) that tools like Nessus, OpenVAS and Metasploit look for. Install software only from official repositories – random .rpm/.deb files or curl | bash scripts can carry malware.

Ravindra Bagale's Tip

Many students type apt on Amazon Linux and yum on Ubuntu. First check the OS with cat /etc/os-release. Amazon Linux/CentOS = yum, Ubuntu = apt. And on Ubuntu, don't forget sudo apt update before installing.

Practice task

Install git, tree and htop on both your Amazon Linux and Ubuntu instances. Then find which package provides /usr/sbin/sshd on each.

Extended teaching notes

Why this lesson matters

Use this lesson to strengthen systems you own: understand the risk, practise safely in a lab, then write and apply the fix.

Apply the fix across stacks

Same class of bug, same idea in every language.

Java / Spring Boot

Parameterise queries, encode output, CSRF tokens, limited Actuator, dependency scanning.

ASP.NET Core

EF Core / parameterised SQL, Razor encoding, HTTPS, Data Protection.

Node.js / Express

helmet, parameterised SQL, npm audit, avoid eval and shell concat.

Python / Django / Flask / FastAPI

ORM, autoescape, pip-audit, Bandit; never shell=True with user input.

PHP / Laravel

PDO/Eloquent, Blade escaping, composer audit.

Go / Ruby

database/sql placeholders / ActiveRecord; html/template / ERB escaping; govulncheck / Brakeman.

nginx / Apache / Tomcat

Hide versions, TLS, security headers, least-open ports.

MySQL / PostgreSQL / MongoDB / Redis

Private networks, auth on, least-privilege users, no 0.0.0.0/0.

AWS / Azure / GCP

Roles not long-lived keys, private data stores, cloud audit logs on.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.