If you attempt to rebuild the links database in Sitecore 8.2 Update 6, 8.2 Update 7, or 9.0 Update 1 you may run into the following error:
System.FormatException: Unrecognized Guid format. Actual value: ---> System.FormatException: Unrecognized Guid format. at System.Guid.GuidResult.SetFailure(ParseFailureKind failure, String failureMessageID, Object failureMessageFormatArgument, String failureArgumentName, Exception innerException) at System.Guid.TryParseGuid(String g, GuidStyles flags, GuidResult& result) at System.Guid..ctor(String g) at Sitecore.Data.ID..ctor(String id)
This is because Sitecore believes a general link or the deprecated “link” field contains an empty ID attribute. While you could modify the links to add an attribute, but Sitecore has released a hotfix (SC Hotfix 220335-1 CMS.Core 11.1.1) to remedy this issue.
This issue is resolved in Sitecore 9.0 Update 2 and later.
To apply the hotfix, download the fix from https://kb.sitecore.net/articles/771795
Once you have it downloaded, extract it and overwrite the CMS website directory with the directories/files in the hotfix.
Important: You will want to backup your CMS before proceeding to apply the hotfix. Once you do, you should have a successful Rebuild Links database such as follows: