In Linux system administration, both useradd and adduser serve the purpose of creating new user accounts, but they approach this task differently.

# Basic useradd command
sudo useradd newusername

# Basic adduser command
sudo adduser newusername

useradd is a low-level utility that comes as part of the shadow-utils package. It's the barebones command that simply creates an entry in system files without any additional configuration.

adduser, on the other hand, is a Perl script that acts as a friendly front-end to useradd. It provides an interactive experience and handles many configuration aspects automatically.

• Interactive vs Non-interactive: adduser prompts for information while useradd requires all parameters in the command
• Default configurations: adduser sets up home directories and copies skeleton files automatically
• Password handling: adduser prompts for password while useradd leaves the account locked

Use useradd when:

# Creating a system user without home directory
sudo useradd -r -s /usr/sbin/nologin serviceuser

# Scripting user creation with specific parameters
sudo useradd -m -d /home/customdir -s /bin/bash -G developers newdev

Use adduser when:

# Quickly creating regular user accounts interactively
sudo adduser john

# When you want the system to handle defaults appropriately
sudo adduser --ingroup developers sarah

For more complex scenarios, you might combine both commands:

# First create user with specific parameters
sudo useradd -m -d /opt/specialuser -s /bin/zsh specialuser

# Then use adduser to configure additional aspects
sudo adduser specialuser audio
sudo adduser specialuser video

Since implementations vary across distributions, it's good to check:

# Check if adduser is a symlink
ls -l $(which adduser)

# View the actual script (on Debian-based systems)
less $(which adduser)

The useradd command is a low-level utility present on all Linux distributions as part of the shadow-utils package. In contrast, adduser is a Perl script wrapper that exists primarily in Debian-based systems (Ubuntu, Mint, etc.), providing more user-friendly interactive features.

# useradd example (basic usage)
sudo useradd -m -s /bin/bash newuser

# adduser example (interactive)
sudo adduser newuser

useradd performs minimal actions by default - it creates an entry in /etc/passwd without creating a home directory or setting up defaults unless explicitly told to. adduser on the other hand:

• Creates home directory by default
• Sets up basic configuration files
• Prompts for additional information (full name, phone, etc.)
• Can set up encrypted home directories

useradd reads defaults from /etc/default/useradd, while adduser uses /etc/adduser.conf. Here's how to examine defaults:

# View useradd defaults
useradd -D

# View adduser configuration
cat /etc/adduser.conf

Use useradd when:

• Writing scripts or automated processes
• Needing fine-grained control over user creation
• Working across different Linux distributions

Use adduser when:

• Interactively creating users on Debian systems
• Wanting the convenience of built-in prompts
• Needing standard configurations applied automatically

Creating a user with specific UID/GID and expiration date:

# Using useradd
sudo useradd -u 1501 -g developers -e 2024-12-31 -c "Temporary contractor" tempuser

# Equivalent with adduser requires manual steps:
sudo adduser --uid 1501 --gid 1001 tempuser
sudo chage -E 2024-12-31 tempuser

Creating system users (no home directory):

# useradd approach
sudo useradd -r -s /usr/sbin/nologin serviceaccount

# adduser equivalent
sudo adduser --system --no-create-home --group serviceaccount