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apt-get

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By Rudra
3 min read
apt-get

apt-get command: Useful usage flags with their explanation and use cases.

This guide walks through important apt-get commands, flags, and how they behave in real systems — including security and pentesting relevance.

Basic Commands

  • Update

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     apt-get update

    What it does?

    • Resynchronizes package index files from configured repositories.
    • Downloads metadata, NOT packages.

    Security Notes

    • Executes APT hooks (Pre-Invoke / Post-Invoke).
    • Uses trusted GPG keys.

    Pentesting Use Cases

    • Detect repository configuration.
    • Abuse hook injection if sudo misconfigured.
    • Recon of available packages.

  • Upgrade

    1

     apt-get upgrade

    What it does?

    • Upgrades installed packages.
    • Does NOT remove packages.

    Security Notes

    • Runs maintainer scripts as root.
    • Uses dpkg backend.

    Pentesting Use Cases

    • Trigger maintainer scripts.
    • Observe package execution behavior.

  • Dist-Upgrade

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     apt-get dist-upgrade

    What it does?

    • Upgrades packages.
    • Handles dependency changes.
    • May remove packages.

    Pentesting Use Cases

    • Trigger large system changes.
    • Study dependency solver behavior.

  • Install Specific Version

    1

     apt-get install curl=8.14.1-2+deb13u2

    What it does?

    • Installs exact package version.

    Pentesting Use Cases

    • Downgrade to vulnerable version.
    • Controlled version testing.

  • Remove

    1

     apt-get remove package_name

    What it does?

    • Removes package.
    • Keeps configuration files.

    Security Notes

    • Executes prerm and postrm scripts.

  • Purge

    1

     apt-get purge package_name

    What it does?

    • Removes package and configuration files.

Source & Build Related Commands

  • Download Source

    1

     apt-get source package_name

    Requirement

    • deb-src must be enabled.

    What it does?

    • Downloads source code.
    • Does NOT install.

    Pentesting Use Cases

    • Inspect packaging scripts.
    • Review applied patches.
    • Study supply chain.

  • Build Dependencies

    1

     apt-get build-dep package_name

    What it does?

    • Installs build dependencies defined in debian/control.

    Pentesting Use Cases

    • Expand attack surface (dev libraries).
    • Prepare lab environment.

  • Compile From Source

    1

     apt-get source --compile package_name

    What it does?

    • Downloads source.
    • Runs dpkg-buildpackage.
    • Produces .deb.

    Note

    • Does NOT install automatically.

Advanced Flags

  • Download Only

    1

     apt-get install -d package_name

    What it does?

    • Downloads .deb.
    • Does NOT install.

    Pentesting Use Cases

    • Inspect .deb manually.
    • Offline analysis.

  • Simulate

    1

     apt-get -s install package_name

    What it does?

    • Dry-run simulation.
    • Shows dependency changes.

    Pentesting Use Cases

    • Dependency mapping.
    • Safe testing.

  • Assume Yes

    1

     apt-get -y install package_name

    What it does?

    • Automatically answers yes to prompts.

    Security Notes

    • Dangerous in automation.

  • Fix Broken

    1

     apt-get -f install

    What it does?

    • Attempts to fix broken dependencies.

  • Ignore Missing

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     apt-get -m install package_name

    What it does?

    • Ignores missing packages.

Configuration Injection (-o flag)

  • Runtime Config Override

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     apt-get -o Foo::Bar=value command

    What it does?

    • Overrides APT config at runtime.

  • Hook Injection Example

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     sudo apt-get -o APT::Update::Pre-Invoke::="sh -c 'echo test > /tmp/injected'" update

    What it does?

    • Executes command before update runs.

    Pentesting Use Cases

    • Privilege escalation if sudo allows apt-get.

    Defensive Measures

    • Restrict sudo usage.
    • Monitor for -o usage.
    • Use AppArmor / auditd.

Security Relevant Flags

  • Allow Unauthenticated

    1

     apt-get --allow-unauthenticated install package

    What it does?

    • Skips signature verification.

    ⚠️ Dangerous.

  • Force Yes

    1

     apt-get --force-yes install package

    What it does?

    • Forces potentially harmful operations.

  • Target Release

    1

     apt-get -t unstable install package

    What it does?

    • Forces package from specific release.

Package State & dpkg Integration

  • Get Selections

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     dpkg --get-selections

    Shows desired package state:

    • install
    • deinstall
    • purge
    • hold

  • Apply Selections

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     apt-get dselect-upgrade

    Applies dpkg selection database.

Cache Management

  • Clean

    1

     apt-get clean
    • Removes cached .deb files.

  • AutoClean

    1

     apt-get autoclean
    • Removes outdated cached packages only.

Important System Locations

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/etc/apt/sources.list.d/
/etc/apt/apt.conf.d/
/var/lib/dpkg/
/var/cache/apt/archives/

Pentesting Focus Areas

  • Maintainer script execution
  • Hook injection via -o
  • Repository manipulation
  • Downgrade attacks
  • sudo misconfiguration abuse
  • Supply chain inspection
  • dpkg selection manipulation
  • dpkg
  • apt-cache
  • apt-config dump
  • auditd
  • strace

Further Reading

  • https://gtfobins.github.io/gtfobins/apt-get/
  • https://manpages.debian.org/apt-get
  • https://wiki.debian.org/Apt
linux
linux apt package-management pentest
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