Ubuntu Server Management - Time Settings & User Management

This document introduces essential commands for time management and user management on Ubuntu Server.

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1. Time Management

Check Current Status

timedatectl

Change Timezone

Example: To change to Seoul(KST)

# Search for Seoul in the available timezone list
timedatectl list-timezones | grep Seoul

# Set timezone
sudo timedatectl set-timezone Asia/Seoul

NTP Synchronization (Recommended)

Ubuntu Server uses systemd-timesyncd by default. However, for servers requiring high precision (e.g., databases, clusters), dedicated services like Chrony or NTPd are preferred.

Important: Do not run multiple time services simultaneously (e.g., timesyncd + chrony). This will cause conflicts.

Automatically synchronize time with internet servers(systemd-timesyncd):

# Enable default synchronization
sudo timedatectl set-ntp on

# Check status
systemctl status systemd-timesyncd

Manual Time Setting

You must disable NTP before manually setting the time.

# Disable NTP
sudo timedatectl set-ntp off

# Set time (Format: YYYY-MM-DD HH:MM:SS)
sudo date -s "2025-12-17 14:30:00"
# Or
sudo timedatectl set-time "2025-12-17 14:30:00"

# Synchronize hardware clock
sudo hwclock --systohc

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2. User Management

Add/Remove Users

Sudo privileges are required to modify users.

# Add user
sudo adduser {USER NAME}

# Delete user
sudo userdel {USER NAME}

# Delete user + remove home directory (Recommended)
sudo userdel -r {USER NAME}

Change Password

sudo passwd {USER NAME}

Grant sudo Privileges

sudo usermod -aG sudo {USER NAME}