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📘 README – NTP Setup Script (Ubuntu, Asia/Dhaka UTC+6)

Overview

This script installs and configures the NTP service on Ubuntu.
It sets the system timezone to Asia/Dhaka (UTC+6) and restricts NTP access so that only private IP ranges (192.168.0.0/16, 10.0.0.0/8, and 103.135.132.0/23) can query the server. All other networks are denied.

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Features

• ✅ Installs NTP daemon (ntp package).
• ✅ Sets timezone to Bangladesh Standard Time (UTC+6).
• ✅ Configures Asia pool NTP servers for synchronization.
• ✅ Restricts access to private subnets only:
  • 192.168.0.0/16
  • 10.0.0.0/8
  • 103.135.132.0/23
• ❌ Blocks all other external IPs by default.

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Usage

1. Save the Script

Save the script as ntp-private-only.sh.

2. Make Executable

chmod +x ntp-private-only.sh

3. Run the Script

./ntp-private-only.sh

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Verification

After running, check:

timedatectl status   # Verify timezone is Asia/Dhaka (UTC+6)
ntpq -p              # Show NTP peers and sync status

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Access Control Notes

• restrict default ignore → denies all clients by default.
• restrict 127.0.0.1 and restrict ::1 → allow local queries.
• restrict <subnet> mask <netmask> nomodify notrap → allows time queries from specified subnets.
• Only LAN/private ranges and your custom subnet can access NTP.

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Example Config Snippet

restrict default ignore
restrict 127.0.0.1
restrict ::1
restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap
restrict 10.0.0.0 mask 255.0.0.0 nomodify notrap
restrict 103.135.132.0 mask 255.255.254.0 nomodify notrap

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