Troubleshoot issues

This section provides information to help you troubleshoot and resolve or work around common issues that are related to the following tasks:

downloading and installing the DFINITY Canister SDK
creating, building, or deploying canisters
using the dfx command-line interface
running the Internet Computer network locally in a development environment

Ensuring node is available in a project

Because projects rely on webpack to provide the framework for the default front-end, you must have node.js installed in your development environment and accessible in the project directory.

If you want to develop your project without using the default webpack configuration and canister aliases, you can remove the assets canister from the dfx.json file or build your project using a specific canister name. For example, you can choose to build only the hello program without front-end assets by running the following command:
```
dfx build hello
```
If you are using the default webpack configuration and running dfx build fails, you should try running npm install in the project directory then re-running dfx build.
If running npm install in the project directory doesn’t fix the issue, you should check the configuration of the webpack.config.js file for syntax errors.

Migrating an existing project

Currently, there is no automatic migration or backward compatibility for any projects that you might have created using previous versions of the dfx command-line interface. After upgrading to the latest version, you might see error or failure messages if you attempt to build or install a project created with a previous version of the dfx command-line interface.

In many cases, however, you can continue to work with projects from a previous release by manually changing the dfx setting in the dfx.json configuration file, then rebuilding the project to be compatible with the version of the dfx command-line interface you have currently installed.

For example, if you have a project that was created with dfx version 0.4.9, open the dfx.json file in a text editor and change the dfx setting to the latest version or remove the section entirely.

Restarting the local Internet Computer network

In some cases, starting the Internet Computer network locally fails because of replicated state errors. If you encounter issues when running dfx start to start the local Internet Computer network:

In the terminal that displays network operations, press Control-C to interrupt the local network process.
Stop the Internet Computer network by running the following command:
```
dfx stop
```
Restart the Internet Computer in a clean state by running the following command:
```
dfx start --clean
```
The --clean option removes checkpoints and stale state information from your project’s cache so that you can restart the Internet Computer replica and web server processes in a clean state.

Keep in mind, however, that if you reset the state information by running dfx start --clean, your existing canisters are also removed.

After running dfx start --clean, recreate your canisters by running the following commands:

dfx canister create --all
dfx build
dfx canister install --all

Removing the canisters directory

If you run into problems building or deploying canisters after successfully connecting to the Internet Computer and registering canister identifiers, you should remove the canisters directory before attempting to rebuild or redeploy the canisters.

You can remove the canisters directory for a project by running the following command in the project’s root directory:

rm -rf ./.dfx/* canisters/*

Reinstalling dfx

Many of the bugs you might encounter can be addressed by uninstalling and reinstalling the dfx command-line interface. Here are a few ways to reinstall dfx.

If you only have one version of dfx installed in your development environment, you can usually run the following command to uninstall and reinstall the latest version of dfx:

~/.cache/dfinity/uninstall.sh && sh -ci "$(curl -sSL https://sdk.dfinity.org/install.sh)"

If you have modified the location of the dfx binary, you might want run the following command to uninstall the version of dfx that is in your PATH, then reinstall the latest version of dfx:

rm -rf ~/.cache/dfinity && rm $(which dfx) && sh -ci "$(curl -sSL https://sdk.dfinity.org/install.sh)"

Xcode prerequisite

Some versions of the DFINITY Canister SDK prompted you to install Xcode when creating a new project on a macOS computer. The prompt has been removed and the dfx new command does not require you to install any macOS developer tools. However, you should have Developer Command Line Tools installed if you want to create a Git repository for your project.

You can check whether you have the developer tools installed by running xcode-select -p. You can install the developer tools by running xcode-select --install.

Failed build when using VMs

If you are running dfx using a virtual machine image on Ubuntu or CentOS, you might see an error message that looks like this when you attempt to run the dfx build command:

Building hello...
An error occurred:
Io(
    Os {
        code: 2,
        kind: NotFound,
        message: "No such file or directory",
    },
)

Address in use error or orphan processes

If you are developing projects locally, you often have a local version of core Internet Computer processes—collectively referred to as the replica—running either is a separate terminal or in the background. If the running Internet Computer processes do not get properly terminated, you might see operating system errors indicating that an address is already in use or or be unable to stop processes normally using the dfx stop command.

There are several scenarios in which you might encounter this issue. For example, if you run dfx start in a local project directory then change to a different local project directory without first stopping Internet Computer processes, you might see this issue.

If you encounter an issue where you suspect or you receive a message that an address is already in use or that a process is already running in the background, perform the following steps:

Run the following command to see which process is listening to the 8000 port if you are using the default local network binding:
```
lsof -i tcp:8000
```
Run the following command to terminate any orphan processes:
```
killall dfx replica
```
Close the current terminal and open a new terminal window.
In the new terminal, run the following command to run the local Internet Computer in a clean state:
```
dfx start --clean --background
```

Memory leak

Fixing memory leaks is an ongoing process. If you encounter any error messages related to memory leaks, you should do the following:

Run dfx stop to stop currently running processes.
Uninstall dfx to prevent further degradation.
Re-install dfx
Run dfx start to restart replica processes.

Alternatively, you can remove the .cache/dfinity directory and re-install the latest dfx binary. For example:

rm -rf ~/.cache/dfinity && sh -ci "$(curl -sSL https://sdk.dfinity.org/install.sh)"