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Did you read the DNS-O-Matic instructions or not?
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URL Authentication : For web browsers or utilities (fetch, curl, lwp-request) which parse authentification section in URL.
Users need to enter a DNS-O-Matic username and password. DNS-O-Matic usernames are 3-25 characters. DNS-O-Matic passwords are 6-20 characters. All ASCII letters and numbers accepted. Dots, dashes, and underscores allowed, but not at the beginning or end of the string.
Users will also enter a list of hostnames (FQDNs) to be updated.