When examining Debian package versions through dpkg -l, you'll notice they follow a specific format:

[epoch:]upstream_version-[debian_revision]

Let's break down each component with examples from your package list:

The epoch is an optional numeric field preceding the version with a colon (e.g., 2:7.3.429). It's used when:

• Upstream version numbering changes radically (like switching from date-based to semantic versioning)
• Package maintainers need to force an upgrade despite numerically lower version

This comes directly from the original software developers. Common patterns include:

• Semantic versioning (1.2.3)
• Date-based versions (20201231)
• Alpha/beta markers (1.0alpha1)

The part after the hyphen indicates Debian/Ubuntu modifications:

• -1: First Debian packaging
• -ubuntu2: Second Ubuntu-specific modification
• .1: First point release (usually security fixes)

Character	Meaning	Example
~	Pre-release marker (sorts before empty string)	1.5.0-1~webupd8
+	Post-release additions	5.1.1alpha+20110809
-	Separates upstream version from Debian revision	7.3.429-2ubuntu2.1
:	Separates epoch from version	2:7.3.429

• ubuntuX: Ubuntu-specific patches (X=revision number)
• dfsg: Indicates Debian Free Software Guidelines compliant source (non-free files removed)
• buildX: Build number for the same source version
• alpha/beta/rc: Development release status markers

Debian uses the dpkg --compare-versions tool which follows strict rules:

1. Compare epochs (higher always wins)
2. Compare upstream versions character by character
3. Compare debian revisions

Example comparison script:

#!/bin/bash
dpkg --compare-versions "1:2.3.4-5" gt "2.3.4-6" && echo "Newer" || echo "Older"

• 1:1.2.3.4.dfsg-3ubuntu4 (zlib1g): Epoch=1, upstream=1.2.3.4.dfsg, debian_revision=3ubuntu4
• 0.52.11-2ubuntu10 (whiptail): No epoch, upstream=0.52.11, debian_revision=2ubuntu10
• 1.5.0-1~webupd8~precise (wimtools): Upstream=1.5.0, debian_revision=1~webupd8~precise

You can extract version components with these commands:

# Get full version
dpkg-query -W -f='${Version}\n' vim

# Get upstream version only
dpkg-query -W -f='${Version}\n' vim | cut -d- -f1

# Get Debian revision
dpkg-query -W -f='${Version}\n' vim | cut -d- -f2-

• Debian Policy Manual: Version Format
• man dpkg(1) - search for "Version numbering"
• man deb-version(7) - detailed version comparison rules

---

Debian package versions follow a strict format that may appear complex at first glance. A typical version string looks like:

[epoch:]upstream_version-debian_revision

The optional epoch is a single number before the colon. It's used when version numbering schemes change dramatically:

# Compare versions with dpkg
dpkg --compare-versions "1:2.0" gt "2.1" && echo "Newer" || echo "Older"

# Example showing epoch comparison
echo "Package A: 2:1.0 vs Package B: 1:2.0"
dpkg --compare-versions "2:1.0" gt "1:2.0" && echo "A is newer" || echo "B is newer"

The main version number assigned by the original software authors. This may include:

• alpha/beta/rc tags (development versions)
• dfsg indicating Debian Free Software Guidelines compliance
• build numbers or dates (20110809)

Example of version extraction:

# Extract upstream version from full version string
full_version="2:7.3.429-2ubuntu2.1"
upstream_version=$(echo $full_version | cut -d- -f1 | cut -d: -f2)
echo $upstream_version  # Outputs: 7.3.429

This portion reflects Debian/Ubuntu-specific modifications:

• Initial Debian package version (-2)
• Ubuntu-specific changes (ubuntu2.1)
• Security updates (.1 at the end)

Debian uses specific rules for comparing versions:

# Compare versions with various operators
dpkg --compare-versions "1.2.3" lt "1.2.4"  # less than
dpkg --compare-versions "2.0~beta" lt "2.0" # tilde sorts before release
dpkg --compare-versions "1.0+dfsg" gt "1.0" # plus sorts after

Character	Purpose	Sorting Order
~	Pre-release versions	Before empty string
+	Post-release additions	After empty string
-	Separates upstream and Debian versions	N/A

Let's analyze real-world package versions:

# Analyzing wget version
version="1.13.4-2ubuntu1"
echo "Upstream: ${version%-*}"   # 1.13.4
echo "Debian: ${version#*-}"     # 2ubuntu1

# Handling xz-utils with alpha tag
version="5.1.1alpha+20110809-3"
if [[ $version == *alpha* ]]; then
    echo "This is an alpha release"
fi

For complete details, consult:

• Debian Policy Manual - Version Format (Section 5.6.12)
• man 5 deb-version
• Ubuntu Packaging Guide