[Fixed] Error while opening Intellij IDEA due to an already running process – Intellij-idea

The Problem:

While trying to launch Intellij IDEA on macOS, the application encounters an error, preventing its successful opening. The error message indicates that there is an already running instance of the IDE, identified by Process 464, which is still active. This issue prevents the user from accessing and working with Intellij IDEA due to the ongoing process.

The Solutions:

Solution 1: Find and Delete the *.lock* File

If you’re facing the issue of not being able to open Intellij IDEA due to an already running process, you can resolve it by removing the .lock file present in the configuration folder.

Step 1: Locate the Configuration Folder

The location of the configuration folder depends on your operating system:

• Linux: ~/.config/JetBrains/IntelliJIdea2023.2
• Windows: C:\Users\JohnS\AppData\Roaming\JetBrains\IntelliJIdea2023.2
• macOS: ~/Library/Application\ Support/JetBrains/IntelliJIdea2023.2

Step 2: Identify the Latest Version Folder

Within the JetBrains folder, you might find multiple versions of Intellij IDEA, such as IntelliJ IDEA 2023.1 and IntelliJ IDEA 2023.2. Locate the folder corresponding to the latest version.

Step 3: Delete the .lock File

Inside the configuration folder, find and delete the .lock file. This should resolve the conflict caused by the already running process.

Step 4: Re-launch Intellij IDEA

After deleting the .lock file, try launching Intellij IDEA again. It should open without any errors.

Additional Tip:

On Unix-like systems (Linux and macOS), you can use the following command to locate the .lock file:

find ~/ -type f -name '.lock'

This command will search for all files named .lock in your home directory and its subdirectories.

Solution 2: Kill the Running Process

1. Open the Terminal application on your Mac.

2. Run the following command to find the process ID (PID) of the running Intellij IDEA instance:

   ps -ef | grep "IntelliJ IDEA"
   

   This command will display a list of all the processes running on your system. Look for a process with the name "IntelliJ IDEA" and note down its PID.

3. Once you have the PID of the running Intellij IDEA instance, run the following command to kill the process:

   sudo kill -9 {PID}
   

   Replace {PID} with the actual PID of the running Intellij IDEA instance. For example, if the PID is 427, you would run the following command:

   sudo kill -9 427
   

   You may be prompted to enter your Mac user password.

4. After running the above command, try opening Intellij IDEA again. It should now open without the "Cannot connect to already running IDE instance" error.

Solution 3: Terminating the Running Process

The error message suggests that there’s already an instance of Intellij IDEA running in the background, conflicting with your attempt to launch a new instance. To resolve this, you need to identify and terminate the running process.

1. Identify the Running Process:
   • Open the Activity Monitor on your Mac (press “Command + Space” and type “Activity Monitor”).
   • In Activity Monitor, search for “Intellij IDEA” or “java”.
   • Look for the process with the same PID as the one mentioned in the error message (in your case, PID 464).
2. Terminate the Running Process:
   • Select the Intellij IDEA process.
   • Click the “Quit Process” button in the Activity Monitor toolbar (the one with the “X” symbol).
   • If prompted, confirm that you want to terminate the process.

Once you have terminated the running process, try launching Intellij IDEA again. It should start without the “Cannot connect to already running IDE instance” error.

Solution 4: Close Notes (Apple)

If you are encountering the error "Cannot connect to already running instance. Exception: Process 464 is still running" when trying to open IntelliJ IDEA on Mac, you can take the following steps to resolve the issue:

1. Open the terminal and run the command ps -ef | grep 464. This command will show you the processes that are currently running with the process ID 464.

2. You will likely find that the process "Notes" (Apple’s note-taking application) is using the process ID 464.

3. Quit the Notes application.

4. Try opening IntelliJ IDEA again. It should now open without any issues.

This solution effectively addresses the problem by identifying and closing the application that is causing the conflict. It offers a clear and concise way to resolve the issue, ensuring that IntelliJ IDEA can be opened and used as expected.

Solution 5: Delete the *.lock* file

Deleting the *.lock* file is known to resolve the error “Cannot connect to already running IDE instance” in Intellij IDEA on Mac. Here’s a step-by-step guide to do it:

1. Open the Terminal application on your Mac.
2. Type the following command to navigate to your home directory:

cd ~

3. Type the following command to navigate to the .config/JetBrains directory:

cd .config/JetBrains

4. Locate the folder for the Intellij IDEA version you are using. It should be named something like IntellijIdea2020.2 or IntellijIdea2021.1.

cd IntellijIdea[version]

5. Delete the .lock file. It should be named something like ide.lock or system.lock.

rm ide.lock

6. Try opening Intellij IDEA again. It should now open without the error.

Video Explanation: