How to Kill a Process Running on a Particular Port in Linux

When a process is occupying a port you need to use, or when a service becomes unresponsive, you'll need to identify and terminate the process using that specific port. Linux provides several methods to find and kill processes by port number.

Prerequisites

You'll need access to a Linux terminal with sudo privileges for killing processes owned by other users. The commands shown work on most Linux distributions.

Method 1: Using lsof Command

The lsof (List Open Files) command is one of the most reliable ways to find processes using specific ports. To find what's running on port 8080:

lsof -i :8080

This command will show output similar to:

COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
node    1234 user   10u  IPv4  12345      0t0  TCP *:8080 (LISTEN)

To kill the process, use the PID from the output:

kill 1234

You can combine both commands in a single line:

kill $(lsof -t -i:8080)

The -t flag tells lsof to return only the process ID, making it perfect for piping to kill.

Method 2: Using netstat and kill

The netstat command can also identify processes using specific ports:

netstat -tlnp | grep :8080

This shows output like:

tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN 1234/node

Extract the PID (1234 in this example) and kill it:

kill 1234

To automate this process:

kill $(netstat -tlnp | grep :8080 | awk '{print $7}' | cut -d'/' -f1)

Method 3: Using fuser Command

The fuser command can directly kill processes using a specific port:

fuser -k 8080/tcp

The -k flag kills the processes immediately. Be careful with this command as it doesn't ask for confirmation.

To see which processes would be killed first:

fuser 8080/tcp

Method 4: Using ss Command

The modern ss command (replacement for netstat) can also identify processes:

ss -tlnp | grep :8080

The output format is similar to netstat:

LISTEN 0 128 *:8080 *:* users:(("node",pid=1234,fd=10))

Extract and kill the process:

kill $(ss -tlnp | grep :8080 | sed 's/.*pid=\([0-9]*\).*/\1/')

Forcing Process Termination

If a process doesn't respond to the regular kill command, use kill -9 for forceful termination:

kill -9 1234

Or with lsof:

kill -9 $(lsof -t -i:8080)

Killing Multiple Processes on Same Port

Sometimes multiple processes might use the same port. To kill all of them:

lsof -t -i:8080 | xargs kill

For forceful termination:

lsof -t -i:8080 | xargs kill -9

Creating a Reusable Function

Add this function to your .bashrc or .zshrc for easy reuse:

killport() {
    if [ -z "$1" ]; then
        echo "Usage: killport <port_number>"
        return 1
    fi

    local pid=$(lsof -t -i:$1)
    if [ -z "$pid" ]; then
        echo "No process found running on port $1"
        return 1
    fi

    echo "Killing process $pid running on port $1"
    kill $pid
}

After adding this function, reload your shell configuration:

source ~/.bashrc

Now you can simply run:

killport 8080

Checking for UDP Processes

The examples above focus on TCP connections. For UDP processes, modify the commands:

lsof -i udp:53
fuser -k 53/udp
ss -ulnp | grep :53

Common Use Cases

Web Development: Kill development servers occupying ports:

killport 3000  # React development server
killport 8000  # Django development server

Database Management: Free up database ports:

killport 3306  # MySQL
killport 5432  # PostgreSQL

Debugging Network Issues: Identify and stop conflicting services:

lsof -i :80   # Check what's using HTTP port
lsof -i :443  # Check what's using HTTPS port

Troubleshooting

If you get "Permission denied" errors, the process might be owned by another user. Use sudo:

sudo kill $(sudo lsof -t -i:8080)

For systemd services, consider using systemctl instead:

sudo systemctl stop apache2
sudo systemctl stop nginx

Next Steps

Now that you can kill processes by port, you might want to learn about:

• Monitoring network connections with netstat and ss
• Managing services with systemctl
• Setting up port forwarding and firewall rules
• Process monitoring with htop and ps