Managing complex cloud services requires standard operational documentation, but its sheer volume often hinders cloud engineers from efficient knowledge acquisition. Retrieval-Augmented Generation (RAG) can streamline this process by retrieving relevant knowledge and generating concise, referenced answers. However, deploying a reliable RAG-based chatbot for cloud operation remains a challenge. In this experience paper, we analyze the development and deployment of RAG-based chatbots for operational question answering (OpsQA) at a large-scale cloud vendor. Through an empirical study of 2,000 real-world queries across three operational teams, we identify five unique OpsQA intent types (e.g., symptom analysis and terminology explanation) and their corresponding requirements for a satisfactory answer, which differ from general software engineering queries. Our analysis further uncovers six root causes leading to chatbot failures—over half stem from query issues (i.e., incompleteness, out-of-scope, or invalid queries), while others are from retrieval or generation issues. To address these issues, we propose iKnow, an intent-guided RAG-based chatbot that integrates intent detection, query rewriting tailored to each intent, and missing knowledge detection to enhance answer quality. In internal evaluations, iKnow improves average answer accuracy from 65.8% to 81.3% with only a modest increase in latency. iKnow has been deployed for six months at CloudA, supporting thousands of cloud engineers in daily operations. We discuss lessons learned from real-world deployment, providing valuable insights for future research and practical implementations in similar domains.