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Running Agent as Background Process

This guide covers methods to run the EPMware Agent as a background process on Linux servers, ensuring continuous operation even after terminal sessions end.

Background Execution Methods

Method 1: Using Ampersand (&)

The simplest method to run the agent in the background:

cd /home/[username]
./ew_target_service.sh &

The & symbol runs the process in the background, returning control to the terminal immediately.

Advantages: - Simple and quick - No additional tools required

Disadvantages: - Process may terminate when terminal session ends - No automatic restart on failure - Limited process management capabilities

Method 2: Using nohup

Run the agent immune to hangups (terminal closure):

cd /home/[username]
nohup ./ew_target_service.sh > /dev/null 2>&1 &

Breaking down the command: - nohup - Prevents process termination on terminal logout - > /dev/null - Redirects standard output to null device - 2>&1 - Redirects error output to standard output - & - Runs in background

Save output to log file: 

nohup ./ew_target_service.sh > agent-nohup.log 2>&1 &
echo $! > agent.pid  # Save process ID for later reference

Method 3: Using screen

Screen provides a virtual terminal that persists after disconnection:

Install screen (if needed): 

# RHEL/CentOS
sudo yum install screen

# Ubuntu/Debian
sudo apt-get install screen

Start agent in screen session: 

# Create new screen session named 'epmware-agent'
screen -S epmware-agent

# Inside screen session, start the agent
cd /home/[username]
./ew_target_service.sh

# Detach from screen (Ctrl+A, then D)

Screen session management: 

# List active sessions
screen -ls

# Reattach to session
screen -r epmware-agent

# Kill a session
screen -X -S epmware-agent quit

Method 4: Using tmux

Tmux is a modern alternative to screen:

Install tmux: 

# RHEL/CentOS
sudo yum install tmux

# Ubuntu/Debian
sudo apt-get install tmux

Start agent in tmux: 

# Create new tmux session
tmux new -s epmware-agent

# Start the agent
cd /home/[username]
./ew_target_service.sh

# Detach from tmux (Ctrl+B, then D)

Tmux session management: 

# List sessions
tmux ls

# Attach to session
tmux attach -t epmware-agent

# Kill session
tmux kill-session -t epmware-agent

System Service Configuration

For production environments, configure the agent as a systemd service:

Create service file: 

sudo nano /etc/systemd/system/epmware-agent.service

Service file content: 

[Unit]
Description=EPMware Agent Service
After=network.target
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=30
User=[username]
WorkingDirectory=/home/[username]
ExecStart=/usr/bin/java -jar /home/[username]/epmware-agent.jar --spring.config.name=agent
StandardOutput=append:/home/[username]/logs/agent-service.log
StandardError=append:/home/[username]/logs/agent-service-error.log

# Environment variables
Environment="JAVA_HOME=/usr/lib/jvm/java-1.8.0"
Environment="PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"

# Resource limits
LimitNOFILE=65536
LimitNPROC=32768

[Install]
WantedBy=multi-user.target

Enable and start service: 

# Reload systemd configuration
sudo systemctl daemon-reload

# Enable service to start on boot
sudo systemctl enable epmware-agent

# Start the service
sudo systemctl start epmware-agent

# Check service status
sudo systemctl status epmware-agent

Service management commands: 

# Stop service
sudo systemctl stop epmware-agent

# Restart service
sudo systemctl restart epmware-agent

# View logs
sudo journalctl -u epmware-agent -f

# Disable auto-start
sudo systemctl disable epmware-agent

Creating an init.d Script (Legacy Systems)

For older systems without systemd:

Create init script: 

sudo nano /etc/init.d/epmware-agent

Script content: 

#!/bin/bash
# chkconfig: 2345 95 05
# description: EPMware Agent Service

AGENT_USER="[username]"
AGENT_HOME="/home/$AGENT_USER"
PIDFILE="$AGENT_HOME/agent.pid"
LOGFILE="$AGENT_HOME/logs/agent-init.log"

start() {
    if [ -f $PIDFILE ]; then
        echo "Agent already running (PID: $(cat $PIDFILE))"
        exit 1
    fi

    echo "Starting EPMware Agent..."
    su - $AGENT_USER -c "cd $AGENT_HOME && nohup ./ew_target_service.sh > $LOGFILE 2>&1 & echo \$! > $PIDFILE"
    echo "Agent started (PID: $(cat $PIDFILE))"
}

stop() {
    if [ ! -f $PIDFILE ]; then
        echo "Agent is not running"
        exit 1
    fi

    echo "Stopping EPMware Agent..."
    kill $(cat $PIDFILE)
    rm -f $PIDFILE
    echo "Agent stopped"
}

status() {
    if [ -f $PIDFILE ]; then
        PID=$(cat $PIDFILE)
        if ps -p $PID > /dev/null; then
            echo "Agent is running (PID: $PID)"
        else
            echo "Agent is not running (stale PID file)"
            rm -f $PIDFILE
        fi
    else
        echo "Agent is not running"
    fi
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        sleep 2
        start
        ;;
    status)
        status
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|status}"
        exit 1
        ;;
esac

Make script executable and enable: 

# Make executable
sudo chmod +x /etc/init.d/epmware-agent

# Add to startup
sudo chkconfig --add epmware-agent
sudo chkconfig epmware-agent on

# Start service
sudo service epmware-agent start

Process Management

Finding the Agent Process

# Find by process name
ps -ef | grep -i epmware-agent | grep -v grep

# Find by user
ps -u [username] | grep java

# Get detailed information
ps aux | grep epmware-agent

# Using pgrep
pgrep -f epmware-agent

Monitoring Process Status

# Check if process is running
if pgrep -f epmware-agent > /dev/null; then
    echo "Agent is running"
else
    echo "Agent is not running"
fi

# Monitor in real-time
top -p $(pgrep -f epmware-agent)

# Check process tree
pstree -p $(pgrep -f epmware-agent)

Managing Process Priority

# Run with lower priority (nice value 10)
nice -n 10 ./ew_target_service.sh &

# Change priority of running process
renice -n 5 -p $(pgrep -f epmware-agent)

# Run with real-time priority (requires root)
sudo chrt -f 50 ./ew_target_service.sh

Auto-Restart Configuration

Using Supervisor

Install and configure Supervisor for process management:

Install Supervisor: 

# RHEL/CentOS
sudo yum install supervisor

# Ubuntu/Debian
sudo apt-get install supervisor

Configure agent in Supervisor: 

# /etc/supervisor/conf.d/epmware-agent.conf
[program:epmware-agent]
command=/home/[username]/ew_target_service.sh
directory=/home/[username]
user=[username]
autostart=true
autorestart=true
startsecs=10
startretries=3
stdout_logfile=/home/[username]/logs/agent-supervisor.log
stderr_logfile=/home/[username]/logs/agent-supervisor-error.log
environment=JAVA_HOME="/usr/lib/jvm/java-1.8.0",PATH="/usr/bin:/usr/local/bin"

Manage with Supervisor: 

# Reload configuration
sudo supervisorctl reread
sudo supervisorctl update

# Start/stop/restart
sudo supervisorctl start epmware-agent
sudo supervisorctl stop epmware-agent
sudo supervisorctl restart epmware-agent

# Check status
sudo supervisorctl status epmware-agent

Using a Watchdog Script

Create a custom watchdog to monitor and restart the agent:

#!/bin/bash
# /home/[username]/agent-watchdog.sh

AGENT_HOME="/home/[username]"
PIDFILE="$AGENT_HOME/agent.pid"
LOGFILE="$AGENT_HOME/logs/watchdog.log"

while true; do
    if [ -f $PIDFILE ]; then
        PID=$(cat $PIDFILE)
        if ! ps -p $PID > /dev/null; then
            echo "$(date): Agent died, restarting..." >> $LOGFILE
            cd $AGENT_HOME
            ./ew_target_service.sh &
            echo $! > $PIDFILE
        fi
    else
        echo "$(date): No PID file, starting agent..." >> $LOGFILE
        cd $AGENT_HOME
        ./ew_target_service.sh &
        echo $! > $PIDFILE
    fi
    sleep 60
done

Run watchdog in background: 

nohup ./agent-watchdog.sh > /dev/null 2>&1 &

Resource Limits and Tuning

Setting Resource Limits

Configure system limits for the agent process:

Edit limits configuration: 

# /etc/security/limits.d/epmware-agent.conf
[username] soft nofile 65536
[username] hard nofile 65536
[username] soft nproc 32768
[username] hard nproc 32768
[username] soft memlock unlimited
[username] hard memlock unlimited

JVM Tuning for Background Operation

Optimize Java settings in the service script:

# Modified ew_target_service.sh
JAVA_OPTS="-Xms512m -Xmx2g -XX:+UseG1GC -XX:MaxGCPauseMillis=100"
java $JAVA_OPTS -jar epmware-agent.jar --spring.config.name=agent

Troubleshooting Background Processes

Process Won't Stay Running

  1. Check for errors in logs: 

    tail -100 logs/agent.log

  2. Verify Java is in PATH: 

    which java
echo $JAVA_HOME

  3. Check file permissions: 

    ls -la ew_target_service.sh
ls -la epmware-agent.jar

Process Consumes Too Many Resources

  1. Limit CPU usage: 

    cpulimit -p $(pgrep -f epmware-agent) -l 50

  2. Limit memory in service file: 

    # Add to systemd service
MemoryLimit=2G

Can't Find Running Process

# Check all Java processes
jps -l

# Check by port (if agent uses specific port)
netstat -tlnp | grep [port]

# Check system logs
journalctl -xe | grep epmware

Best Practices

  1. Always use a service manager (systemd, init.d, or Supervisor) for production
  2. Configure automatic restart on failure
  3. Set appropriate resource limits to prevent system impact
  4. Monitor process health with external tools
  5. Maintain separate log files for service and application
  6. Document your configuration for team reference
  7. Test failover scenarios regularly