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Troubleshooting prebuilds

You can use prebuilds to speed up the creation of codespaces. This article provides troubleshooting steps for common issues with prebuilds.

GitHub Codespaces está disponible para las organizaciones que usen GitHub Team o GitHub Enterprise Cloud. GitHub Codespaces también está disponible como versión beta limitada para usuarios individuales en los planes GitHub Free y GitHub Pro. Para más información, vea "Productos de GitHub".

For more information about GitHub Codespaces prebuilds, see "Prebuilding your codespaces."

Checking whether a codespace was created from a prebuild?

When you create a codespace, you can choose the type of the virtual machine you want to use. If a prebuild is available for the type of virtual machine, " Prebuild ready" is shown next to it.

A list of available machine types

If you have your GitHub Codespaces editor preference set to "Visual Studio Code for Web" then the "Setting up your codespace" page will show the message "Prebuilt codespace found" if a prebuild is being used.

The 'prebuilt codespace found' message

Similarly, if your editor preference is "VS Code" then the integrated terminal will contain the message "You are on a prebuilt codespace defined by the prebuild configuration for your repository" when you create a new codespace. For more information, see "Setting your default editor for GitHub Codespaces."

After you have created a codespace you can check whether it was created from a prebuild by running the following GitHub CLI command in the terminal:

Shell
gh api /user/codespaces/$CODESPACE_NAME --jq .prebuild

This returns true if the codespace was created using a prebuild.

Alternatively, if GitHub CLI (gh) is not installed, you can use the following command, which returns createFromPrebuild if the codespace was created from a prebuild:

Shell
cat /workspaces/.codespaces/shared/environment-variables.json | jq '.ACTION_NAME'

The "Prebuild Ready" label is sometimes missing

You may notice that sometimes, when you create a new codespace from a prebuild-enabled branch, the " Prebuild Ready" label is not displayed in the dialog box for choosing a machine type. This means that prebuilds are not currently available.

By default, each time you push to a prebuild-enabled branch, the prebuild is updated. If the push involves a change to the dev container configuration then, while the update is in progress, the " Prebuild Ready" label is removed from the list of machine types. During this time you can still create codespaces without a prebuild. If required, you can reduce the occasions on which prebuilds are unavailable for a repository by setting the prebuild to be updated only when you make a change to your dev container configuration files, or only on a custom schedule. For more information, see "Configuring prebuilds."

If your branch is not specifically enabled for prebuilds it may still benefit from prebuilds if it was branched from a prebuild-enabled branch. However, if the dev container configuration is changed on your branch, so that it's not the same as the configuration on the base branch, prebuilds will no longer be available on your branch.

Here are things to check if the " Prebuild Ready" label is not displayed for a particular branch:

  • Confirm that a prebuild configuration exists for this branch. If you’re not a repository administrator, you'll need to reach out to one to confirm this.
  • Confirm that the prebuild configuration includes your region.
  • Check whether a change to the dev container configuration was pushed to the prebuild-enabled branch recently. If so, you will typically have to wait until the prebuild workflow run for this push completes before prebuilds are available again.
  • If no configuration changes were recently made, go to the Actions tab of your repository, click Codespaces Prebuilds in the workflows list, and check that prebuild workflow runs for the branch are succeeding. If latest runs of a workflow failed, and one or more of these failed runs contained changes to the dev container configuration, then there will be no available prebuilds for the associated branch.

Some resources cannot be accessed in codespaces created using a prebuild

If the devcontainer.json configuration file for a prebuild configuration specifies that permissions for access to other repositories are required, then the repository administrator is prompted to authorize these permissions when they create or update the prebuild configuration. If the administrator does not grant all of the requested permissions there's a chance that problems may occur in the prebuild, and in codespaces created from this prebuild. This is true even if the user who creates a codespace based on this prebuild does grant all of the permissions when they are prompted to do so.

Troubleshooting failed workflow runs for prebuilds

If the devcontainer.json configuration file for a prebuild configuration is updated to specify that permissions for access to other repositories are required, and a repository administrator has not been prompted to authorize these permissions for the prebuild configuration, then the prebuild workflow may fail. Try updating the prebuild configuration, without making any changes. If, when you click Update, the authorization page is displayed, check that the requested permissions are appropriate and, if so, authorize the request. For more information, see "Managing prebuilds" and "Managing access to other repositories within your codespace."

If the workflow runs for a prebuild configuration are failing, you can temporarily disable the prebuild configuration while you investigate. For more information, see "Managing prebuilds."

Further reading