How to Fix UniFi Controller Startup Failed Error

How to Fix UniFi Controller Startup Failed Error

When attempting to upgrade UniFi controller software or launch this software, an error message pops up “UniFi controller startup failed”. According to an investigation, insufficient free space on system drive is the major cause behind this error. In this situation, you can use a junk file cleaner to delete unnecessary files or extend the system drive to create more free space. 

UniFi controller startup failed

In addition, other factors like incompatible Java, corrupted UniFi logs and glitches can trigger UniFi controller not starting. Now, let’s explore how to fix UniFi controller startup failed.

Fix 1. Close AllUniFi Controller Related Processes

Conflicting processes can cause temporary software glitches, which trigger “UniFi controller failed to start”. Follow the steps below to end all UniFi controller related processes.

Step 1. Right click on Start button and choose Task Manager.

Task Manager

Step 2. Select the process related to the UniFi controller and click on End task button. Then repeat this step to end all related processes including Java and MongoDB.

Fix 2. Add a New User

If Windows Profile username has special characters like á, ì, ô, and ç, this software won’t find the file and throws error “UniFi controller startup failed”. If there are any special characters, follow the steps below to create a new user profile.

Step 1. Boot your computer into Safe Mode.

Step 2. Open the Settings app and click on Accounts.

Step 3. Refer to Other people and choose Add someone else to this PC.

Other people

Step 4. Click I don’t have this person’s sign-in information.

Step 5: Refer to Add a user without a Microsoft account. Then enter a user name and assign a password, and click Next.

Microsoft account

Step 6. Transfer all your personal data to the new user profile.

Fix 3. Set the Default Port for UniFi Controller

UniFi controller startup failed error also appears when the default port is occupied by other programs. In most cases, the UniFi controller software requires port 8080 to runnormally. Here you need to check if the default port is used by a problematic program. If it is, you need to set the default port for UniFi controller manually.

Fix 4. Rename the UniFi Logs

Log files are created while running the UniFi controller software. Once these log files are missing or corrupted, your UniFi controller won’t start. So, you need to rename these log files and then new log files will be created. 

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Step 1. End all UniFi-related processes via Task Manager.

Step 2. Open your File Explorer, and then navigate to the UniFi controller directory folder. The directory is usually located in This PC > Local Disk C > Ubiquiti UniFi > logs.

UniFi Logs

Step 3. Rename these log files in UniFi controller directory. Then add the .old at the end of the file name extension, and rename the server and mongoDB log files.

Step 4. Relaunch the software and check if the UniFi controller startup failed error still persists.

Fix 5. Change the Specified Storage Engine

Some users explain that the UniFi controller won’t start when database was created by the “mmapv1” storage engine, but the specified storage engine is “wiredTiger”. In this case, you can force the UniFi controller to use the mmapv1 storage engine.

Step 1. Open the File Explorer and find the UniFi controller directory folder.

Step 2. Open the System.Properties file with Notepad and add the following line to the end of the text.


Step 3. Save the changes and exit.

Now, relaunch the program and check if the issue is resolved.

Fix 6 Reinstall Java

As you might know, the JAVA version 9 is not supported for the UniFi Network Controller. So, uninstall your current Java and install a right version.

Step 1. Input control in the search box and choose the Control Panel.

Step 2 Change the View by type to Category and click on Uninstall a Program under the Programs tab.

Uninstall a Program

Step 3. Right click the Java and select Uninstall. Then following the on-screen prompts to complete this uninstallation.

Step 4. Click here to download the 64-bit Java version 8 and install it. If you are prompted with a message saying Firewall to allow Java, allow it.

Fix 7. Set the UniFi Controller as a Service

If the UniFi controller is not installed as a service, you may encounter this error. To fix the issue, install the controller as a service.

Step 1. Open the environment variables, and then add the Java path C:\Program Files(x86)\Java\jre7\bin\javaw.exe at the end of the path in the Temp variable.

Step 2. Click OK to save the changes.

environment variables

Step 3. Run the Command Prompt as an administrator and type the following commands and hit Enter after typing each command.

  • cd “%UserProfile%\Ubiquiti UniFi\”
  • java -jar lib\ace.jar installsvc

Step 4. When the Complete Installation appears, type java -jar lib\ace.jar startsvc and hit Enter.

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