Tomcat Installation and Initial Setup

Apache Tomcat is the leading WAS (Web Application Server) for running Java Servlets and JSP. This chapter covers everything you need in production: JDK environment setup, version differences across Tomcat releases, and the directory structure after installation.

---

JDK Environment Setup

Tomcat requires a Java runtime. The minimum Java version required differs by Tomcat version.

Tomcat Version	Minimum Java	Servlet Spec	JSP Spec	Recommendation
Tomcat 9	Java 8+	4.0	2.3	Legacy systems
Tomcat 10	Java 11+	5.0	3.0	Jakarta EE migration
Tomcat 10.1	Java 11+	6.0	3.1	** Recommended (stable)**
Tomcat 11	Java 17+	6.1	4.0	Latest features

Important: From Tomcat 10, the javax.* package namespace changed to jakarta.*. Code modifications are required when migrating from Tomcat 9 → 10.

Ubuntu — OpenJDK Installation

# Install OpenJDK 17 LTS (recommended for Tomcat 10.1+)
sudo apt update
sudo apt install -y openjdk-17-jdk

# Verify version
java -version
# openjdk version "17.0.x" ...

# Set JAVA_HOME (permanent)
echo 'export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64' | sudo tee -a /etc/environment
echo 'export PATH=$PATH:$JAVA_HOME/bin' | sudo tee -a /etc/environment
source /etc/environment

echo $JAVA_HOME
# /usr/lib/jvm/java-17-openjdk-amd64

CentOS/RHEL — OpenJDK Installation

# Install OpenJDK 17
sudo dnf install -y java-17-openjdk-devel

# Check JAVA_HOME
alternatives --list | grep java

# Create /etc/profile.d/java.sh
cat << 'EOF' | sudo tee /etc/profile.d/java.sh
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk
export PATH=$PATH:$JAVA_HOME/bin
EOF
source /etc/profile.d/java.sh

---

Installing Tomcat on Ubuntu/Debian

Method 1: APT Package Manager (Quick)

sudo apt update
sudo apt install -y tomcat10

# Check service status
sudo systemctl status tomcat10
sudo systemctl enable tomcat10
sudo systemctl start tomcat10

# Verify on default port 8080
curl -I http://localhost:8080
# HTTP/1.1 200

Method 2: Official Distribution (Recommended — Version Control)

# Prepare installation directory
sudo mkdir -p /opt/tomcat

# Create dedicated user (security)
sudo useradd -r -m -U -d /opt/tomcat -s /bin/false tomcat

# Download Tomcat 10.1
TOMCAT_VERSION=10.1.20
cd /tmp
wget https://dlcdn.apache.org/tomcat/tomcat-10/v${TOMCAT_VERSION}/bin/apache-tomcat-${TOMCAT_VERSION}.tar.gz

# Extract
sudo tar -xzf apache-tomcat-${TOMCAT_VERSION}.tar.gz -C /opt/tomcat/
sudo ln -s /opt/tomcat/apache-tomcat-${TOMCAT_VERSION} /opt/tomcat/latest

# Set ownership
sudo chown -R tomcat: /opt/tomcat/latest
sudo chmod +x /opt/tomcat/latest/bin/*.sh

# Register Systemd service
sudo tee /etc/systemd/system/tomcat.service << 'EOF'
[Unit]
Description=Apache Tomcat Web Application Container
After=network.target

[Service]
Type=forking
User=tomcat
Group=tomcat

Environment="JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64"
Environment="CATALINA_HOME=/opt/tomcat/latest"
Environment="CATALINA_BASE=/opt/tomcat/latest"
Environment="CATALINA_PID=/opt/tomcat/latest/temp/tomcat.pid"
Environment="CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC"

ExecStart=/opt/tomcat/latest/bin/startup.sh
ExecStop=/opt/tomcat/latest/bin/shutdown.sh

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable tomcat
sudo systemctl start tomcat
sudo systemctl status tomcat

---

Running Tomcat with Docker

# Official Tomcat 10.1 + JDK 17 image
docker run -d \
  --name tomcat \
  -p 8080:8080 \
  tomcat:10.1-jdk17

# Enable default management page (development only)
docker exec -it tomcat bash -c \
  "cp -r /usr/local/tomcat/webapps.dist/* /usr/local/tomcat/webapps/"

# Verify at http://localhost:8080

Docker Compose Example

# docker-compose.yml
version: '3.8'
services:
  tomcat:
    image: tomcat:10.1-jdk17
    container_name: tomcat-app
    ports:
      - "8080:8080"
    volumes:
      - ./webapps:/usr/local/tomcat/webapps
      - ./conf/server.xml:/usr/local/tomcat/conf/server.xml:ro
      - ./logs:/usr/local/tomcat/logs
    environment:
      - CATALINA_OPTS=-Xms512m -Xmx1024m
    restart: unless-stopped

---

Tomcat Directory Structure

Understanding the directory structure helps you quickly locate configuration files.

$CATALINA_HOME/
├── bin/                  ← Execution scripts
│   ├── startup.sh        # Start Tomcat
│   ├── shutdown.sh       # Stop Tomcat
│   ├── catalina.sh       # Core script (called by startup.sh)
│   └── setenv.sh         # JVM option injection (create if missing)
│
├── conf/                 ← Configuration files
│   ├── server.xml        # Core config (connectors, hosts, contexts)
│   ├── web.xml           # Global servlet configuration
│   ├── context.xml       # Global context configuration
│   ├── tomcat-users.xml  # Admin account configuration
│   └── logging.properties # Log configuration
│
├── webapps/              ← Deployment directory
│   ├── ROOT/             # http://host:8080/ default app
│   ├── manager/          # Tomcat manager web app
│   ├── host-manager/     # Virtual host manager web app
│   └── myapp.war         # WAR file → auto-extracted
│
├── logs/                 ← Log files
│   ├── catalina.out      # Standard output (main log)
│   ├── catalina.YYYY-MM-DD.log  # Daily log
│   ├── localhost.YYYY-MM-DD.log # Virtual host log
│   └── access_log.YYYY-MM-DD.txt # Access log
│
├── lib/                  ← Shared libraries (common to all apps)
│   └── servlet-api.jar, jsp-api.jar, ...
│
├── temp/                 ← Temporary files (JVM temp dir)
└── work/                 ← JSP compile cache
    └── Catalina/
        └── localhost/
            └── ROOT/     # JSP → Java → .class

setenv.sh — JVM Option Configuration

The recommended way to inject JVM options before Tomcat starts.

# Create $CATALINA_HOME/bin/setenv.sh
cat << 'EOF' | sudo tee /opt/tomcat/latest/bin/setenv.sh
#!/bin/bash
# JVM heap memory
export CATALINA_OPTS="$CATALINA_OPTS -Xms512m -Xmx2g"

# GC settings (Java 17 defaults to G1GC)
export CATALINA_OPTS="$CATALINA_OPTS -XX:+UseG1GC"
export CATALINA_OPTS="$CATALINA_OPTS -XX:MaxGCPauseMillis=200"

# GC log (for performance analysis)
export CATALINA_OPTS="$CATALINA_OPTS -Xlog:gc*:file=/opt/tomcat/latest/logs/gc.log:time,uptime:filecount=5,filesize=20m"

# Server mode
export CATALINA_OPTS="$CATALINA_OPTS -server"

# Timezone
export CATALINA_OPTS="$CATALINA_OPTS -Duser.timezone=Asia/Seoul"

# Encoding
export JAVA_OPTS="$JAVA_OPTS -Dfile.encoding=UTF-8"
EOF

sudo chmod +x /opt/tomcat/latest/bin/setenv.sh
sudo chown tomcat: /opt/tomcat/latest/bin/setenv.sh

---

Service Management Commands

# Start / Stop / Restart / Status
sudo systemctl start tomcat
sudo systemctl stop tomcat
sudo systemctl restart tomcat
sudo systemctl status tomcat

# Real-time log monitoring
sudo tail -f /opt/tomcat/latest/logs/catalina.out

# Validate configuration
sudo -u tomcat /opt/tomcat/latest/bin/catalina.sh configtest

# Check port usage
sudo ss -tlnp | grep 8080

---

Firewall Configuration

# Ubuntu/Debian (ufw)
sudo ufw allow 8080/tcp
sudo ufw reload

# CentOS/RHEL (firewalld)
sudo firewall-cmd --permanent --add-port=8080/tcp
sudo firewall-cmd --reload

---

Verifying Installation

# Check Tomcat version
/opt/tomcat/latest/bin/version.sh

# Example output
# Server version: Apache Tomcat/10.1.20
# JVM Version: 17.0.x

# Check HTTP response
curl -s -o /dev/null -w "%{http_code}" http://localhost:8080
# 200

---

Summary

Item	Details
Tomcat version	10.1.x recommended (Java 11+), 11.x (Java 17+)
Java requirement	Tomcat 9: Java 8+, Tomcat 10+: Java 11+
JVM option location	$CATALINA_HOME/bin/setenv.sh (recommended)
Key config files	conf/server.xml, conf/web.xml, conf/context.xml
Deployment directory	webapps/ (WAR auto-extraction)
Service management	systemctl start/stop/restart tomcat