Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::vmmigration_v1::VmMigrationClient(
google::cloud::vmmigration_v1::MakeVmMigrationConnection(options));
}
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis webpage provides documentation for various versions of the \u003ccode\u003evmmigration-override-authentication\u003c/code\u003e, ranging from version 2.11.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe content explains how to override the default authentication credentials used by the client libraries, which typically rely on Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default credentials can be done by providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, and the example code demonstrates loading credentials from a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor more information about the factory functions to create credentials objects, refer to the Authentication Components section in the documentation.\u003c/p\u003e\n"],["\u003cp\u003eThe best practices for managing service account keys can be found in a separate guide linked at the end of the content.\u003c/p\u003e\n"]]],[],null,[]]
