Linux System Management 3

SSH service validation - PXE basics - DNS

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Objectives

Verify and harden SSH server configuration Understand PXE boot role and discovery process Investigate DNS resolution settings and tools Use host, dig, and nslookup to resolve names and test DNS behavior

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Tree

linux-system-management-3/
├── README.md
├── outputs/
│   ├── 01-sshd-status.txt
│   ├── 01b-sshd-port-check.txt
│   ├── 02-sshd-config.txt
│   ├── 03-pxe-theory.txt
│   ├── 04-resolv-nsswitch.txt
│   └── 05-dns-tools-output.txt
└── screenshots/
    ├── 01-sshd-status.png
    ├── 02-sshd-config.png
    ├── 03-pxe-theory.png
    ├── 04-resolv-nsswitch.png
    └── 05-dns-tools-output.png

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Execution

1. SSH Service Status & Port Validation

sudo systemctl status sshd
sudo ss -tuln | grep :22
sudo lsof -i :22

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2. SSHD Config Check (Hardened)

sudo grep -Ei 'permitrootlogin|passwordauthentication|port' /etc/ssh/sshd_config

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3. PXE Theory Notes (Manual)

What is PXE How DHCP and TFTP are used The boot process sequence

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4. DNS Resolution Files

cat /etc/resolv.conf
cat /etc/nsswitch.conf | grep hosts

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5. Name Resolution Tools

host google.com
dig google.com +short
nslookup google.com

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Summary

✅ linux-system-management-1
✅ linux-system-management-2
✅ linux-system-management-3