Reverse DNS Gives an Incorrect Hostname For My Server or Client
From The Open Source Backup Wiki (Amanda, MySQL Backup)
This article is a part of the Troubleshooting collection.
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Problem
A reverse lookup of the IP address of your machine (client or server) gives a hostname which is generated by the ISP, and is not the one you want to use:
# host 123.124.125.126 dyn-126.125.my-isp.com
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Solution
Configure resolution of that IP address locally on the machine(s) which are getting the incorrect hostname:
- Define the IP address in the hosts file (/etc/hosts) on the backup client
XXX.XXX.XXX.XXX amanda.mydomain.com
- Change the name lookup order in /etc/nsswitch.conf file to
hosts: files dns
The lookup order, eg. files dns (and/or ldap, nis, ...) so that hosts file is searched before name servers.
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Explanation
In this situation, the Amanda security layer does a reverse-DNS lookup of the other host's IP address, and thus sees incoming connections as from e.g.,
amanda@dyn-126.125.my-isp.com
instead of the intended
amanda@myserver.mydomain.com
and therefore rejects the connection
