Avoiding slow startup due to hostname resolution issues

Host name resolution issues can cause the NetWorker server to become unresponsive or start very slowly. If the following situation applies to your environment, consider using this the workaround.

  • The NetWorker server uses DNS but the DNS server is not available.
  • The NetWorker server cannot resolve all of its NetWorker client hosts.

Workaround for host name resolution issues

If the NetWorker server starts slowly or becomes unresponsive due to host name resolution issues:

  1. Disable DNS lookup for the host being recovered and utilize the local hosts file on the NetWorker server for hostname resolution.
    • For Windows, the hosts file is located in C:\Windows\System32\Drivers\etc\.
    • For UNIX and Linux, the file is located in /etc.
      Modify the /etc/nsswitch.conf file to look up the hosts files, before DNS, as a hostname resolution method.
  2. Ensure that the hosts file is set up so that the fully qualified domain name (FQDN) is first, and is followed by the corresponding shortname.
    IMPORTANT: If the NetWorker server's client name was originally the shortname, then the shortname needs to be first, followed by the longname. For example, 213.64.10.8 host host.dyndns.org
  3. When the DNS server is available, re-enable DNS lookup.

Making changes to the /etc/nsswitch.conf file

Use the following steps to edit the /etc/nsswitch.conf file:

  1. If the ‘hosts' line in the /etc/nsswitch.conf file contains the following:
    hosts: dns files

    This indicates that the DNS feature will be used first. If the DNS servers are not available or cannot resolve the address, then modify the hosts line to use the /etc/hosts file for hostname resolution, as in the following:
    hosts: files
  2. On the NetWorker server, populate the local hosts file with the known client's valid IP address. For those clients whose IP address is unknown, use 127.0.0.1.
    127.0.0.1 is the standard IP address used for a loopback network connection. When the NetWorker server comes up, a DNS check is performed for each client, and for clients that are not available or offline, the server connects to 127.0.0.1, which immediately loops back to the same machine. This approach helps the NetWorker server to become available faster instead of waiting to resolve all the clients DNS lookup.
  3. When the DNS server is available, re-enable DNS lookup.
    Note:This method for resolving the hostnames is preferred when the NetWorker server is recovered after a DNS server crash.

When the NetWorker server is available, a valid client IP address must be updated in the local hosts file to perform a backup or recovery for the critical clients.

When the DNS server is available and running, remove the client details from the local hosts file.