Question
What is a bootstrap DNS server? When is a bootstrap DNS server needed?
Answer
In computing the term "bootstrap" can mean to initiate a self-sustaining process (the source is this posting). A bootstrap DNS server is a DNS server that allows other domain name entries (such non-IP addresses) to be found by finding a DNS server. If you have hostnames in an /etc/hosts file or similar configuration, the bootstrap DNS server maps and routes hostnames to IP addresses initially (such as to other regular DNS servers). Similar to how /etc/resolv.conf works to point a host server to a specific DNS server, the bootstrap DNS server resolves various entries of hostnames to IP addresses when such hostnames would otherwise not be resolved, mapped or found.
A bootstrap DNS server is needed for a given pod or server for the initial resolution/finding of hostnames that are themselves DNS servers but need mapping from the pod or server. Thus a bootstrap DNS server allows regular DNS to be configured when regular IP address routing is insufficient (e.g., for the first time a server or pod comes online).
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