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Linux Survival Basics

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Check One Installed Package Cleanly

You need to confirm whether one package is installed and capture its exact installed version without noisy apt output.

Command

dpkg-query -W -f='${Status} ${Version}\n' openssl

Before you run this

System impact: Read-only. Low when scoped to the shown target.

When not to use it: Do not use it to find the newest available version; use apt policy for candidate information.

Expected output

A status and version line such as install ok installed 3.0.13-0ubuntu3.5.

System impact

Read-only. Nothing changes. dpkg-query reads the local dpkg database for one package.

Recovery / rollback: no state is changed.

When to use it

Use in runbooks, support tickets, and package audits where one exact installed version matters.

When not to use it

Do not use it to find the newest available version; use apt policy for candidate information.

Watch this command run

Command transcript

This sanitized transcript shows the commands and output shape without exposing host details.

demo@lab:~$

$ dpkg-query -W -f='${Status} ${Version}\n' openssl

install ok installed 3.0.13-0ubuntu3.5

$ dpkg-query -W -f='${Status} ${Version}\n' nginx

install ok installed 1.24.0-2ubuntu7.3
View commands shown

These are the commands shown in the sanitized transcript.

Commands shown

  1. dpkg-query -W -f='${Status} ${Version}\n' openssl
  2. dpkg-query -W -f='${Status} ${Version}\n' nginx

next steps

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Spot Foreign-Architecture Packages

One unexpected architecture can explain confusing dependency output.

dpkg-query -W -f='${Architecture}\t${Package}\n' | awk '$1 != "amd64" && $1 != "all"'
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List Installed Package Versions

A package inventory beats memory when a server is drifting.

dpkg-query -W -f='${Package}\t${Version}\t${Architecture}\n' | sort
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Find Broken or Leftover dpkg States

Not every package row is cleanly installed.

dpkg-query -W -f='${db:Status-Abbrev}\t${Package}\n' | awk '$1 !~ /^ii$/'
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Find Which Package Owns a File

That binary came from somewhere. dpkg can tell you where.

dpkg-query -S /usr/sbin/nginx
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Fingerprint a Debian or Ubuntu Host

Before package triage, prove what OS family and release you are actually on.

. /etc/os-release && printf '%s %s %s\n' "$ID" "$VERSION_ID" "$VERSION_CODENAME"
Study mapping

Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.

  • lpic1:102-package-management
  • lpic1:103-gnu-unix-commands
  • lfcs:essential-commands
  • lfcs:operations-deployment
  • linuxplus:provisional
  • linuxplus:system-management
  • risk:read-only

Useful for

  • LPIC-1 style command-line practice
  • LFCS style performance tasks
  • Linux+ style troubleshooting review

Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.