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I want to create a server for a customer and have that customer finish the configuration for themselves. It was been decided that rather than setting default DNS servers (i.e. something like Google's) that the customer should enter the information by themselves. I assume that the customer is technically competent enough to do this.

If however they forget or neglect to set this up they might spend some time trying to figure out what is wrong and eventually contact support. (In this case, I think that setting a default might have been better.)

Apart from the obvious inability to resolve hosts, what other issues might they face until they have set valid dns servers in resolve.conf?

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I would like this to be a turnkey system too, but I am gathering information of about what issues would occur in order to present a case to the decision maker that this may not be a good idea. –  Stuart Woodward Sep 5 '12 at 8:44
1  
It depends on what software you have configured. e.g. SSH, by default does a reverse DNS lookup, so no DNS means very slow login. –  Matt Sep 5 '12 at 9:47

4 Answers 4

up vote 2 down vote accepted

It depends on what server software is running on the host.

Anything that needs or would result in a DNS lookup basically will not work. Some things may work but run real slow due to DNS lookup failures. Some servers like SSH server by default do reverse DNS lookups on incoming connections. These reverse lookups end up slowing down the remote login process.

Your question doesn't really give much detail so we can't get specific.

If you want it to be a turnkey system then you should provide some initial setup instructions or better still when they first login to the console a script forcing the dns to be setup would be sensible. Once set then that setup script should no longer be called.

Come to think of it, what are you setting the initial IP address to? surely that would need changing too? It makes sense just to use DHCP initially and provide some instructions for static configuration including DNS.

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It's a hosted server somewhat like an Amazon instance. –  Stuart Woodward Sep 5 '12 at 22:16

Not being able to resolve hosts is the issue they'll face.

This means they won't seem to have Internet connectivity and will get strange errors like:

Temporary failure in name resolution

which don't necessarily lead non-technical users to check /etc/resolv.conf.

If at all possible, and these are meant to be turnkey systems, configure your servers with default entries such as those provided by Google Public DNS:

nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 2001:4860:4860::8888
nameserver 2001:4860:4860::8844
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I would like this to be a turnkey system too, but I am gathering information of about what issues would occur in order to present a case to the decision maker that this may not be a good idea –  Stuart Woodward Sep 5 '12 at 8:47
1  
Delete the DNS servers from the decision maker's computer. He'll get it pretty fast. –  Michael Hampton Sep 5 '12 at 8:49
    
He uses windows. I'm asking specifically about Linux... –  Stuart Woodward Sep 5 '12 at 22:15
    
Perhaps so, but the issues are the same. And it would make for a powerful demonstration when making your case. –  Michael Hampton Sep 5 '12 at 22:16

They will not be able to resolve DNS names. That's it. Being unable to resolve DNS names means you can not access Internet resources as most if not all resources are addressed using names such as web addresses / email addresses, etc...

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..this is what I meant by "obvious inability to resolve hosts". I was thinking of other side effects that would not be so apparent. e.g. if the ntp settings included the host name then the time would drift. –  Stuart Woodward Sep 5 '12 at 8:46

Why make things harder than they need to be? Configure the file with some defaults and advise the customer that they may wish to alter them. If they're technical enough they can make the changes, if they so desire. If they're not technical I'm sure they will be more grateful for receiving a working system.

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I would like this to be a turnkey system too, but I am gathering information of about what issues would occur in order to present a case to the decision maker that this may not be a good idea –  Stuart Woodward Sep 5 '12 at 8:46
    
@Stuart, It's far better to avoid issues than to find out what they might be. It's a bit like getting run over by a bus. I'd rather avoid it than find out what it might feel like. –  John Gardeniers Sep 5 '12 at 11:43
    
I'm trying to gather the information about specific problems that will occur in order to make a case to someone that this is not a good idea. The answers which mention SSH reverse lookups failing are a good example which the customer would encounter when they first logged into their un-configured box. –  Stuart Woodward Sep 5 '12 at 22:21

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