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Using Webmin → Network Configuration, I added a new DNS address to the existing server (10.100.200.300). While I saved the new configuration, I lost access to webmin and ssh to this server.

How can I retrieve access?

I pinged 10.100.200.300 and its dead.

When I tried to login with ssh it says: error no route to host. I usually log in to webmin the server IP address and port 10000 but now I cannot.

Any help to go back to my previous state?

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it sounds like a routing issue? Could you describe your network layout? Is the computer trying to access the server on the same network? –  tomodachi Sep 30 '12 at 11:00
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4 Answers

you should not use webmin. It is well known to break easily systems. For instance, "in one clic" webmin blasted your network configuration. And the worse is that changing DNS under any linux is really easy : you just need to edit the file /etc/resolv.conf

You must log in localy (keyboard and screen) to your server. You lost your network connection. It seems that you lost your routes.

Maybe your network is down and you just need to do a service networking restart

What is sure is that you will not be able to do anything remotely.

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im new to linux so i use webmin because it is easier for me to manage, but still i have a little experience. adding a new recort to webmin->network configuration->hostname and dns clients, this is changing /etc/resolv.conf?? if it is right i should delete the entry i added using webmin and i hope problem fixed. –  xloumbos Sep 30 '12 at 11:21
    
Sadly the trouble you are having is not related to dns or hostname. That's why I said that it's unwise to use webmin. For the hostname there is two files : /etc/hosts and /etc/hostname. Please post the result of the route command that you can type in any console. –  Antoine Rodriguez Sep 30 '12 at 11:31
    
Any tool in Linux if used improperly can cause unintended consequences and/or "break" a system. Telling this user not to use webmin because it "could break his system" is akin to telling him/her not to use the terminal for the same reason. –  Argusvision Oct 21 '12 at 21:09
    
@Argusvision : You're mixing things : Where the terminal is a powerful tool that can indeed break your system if misused, Webmin is a tool that can powerfully break your system even with a correct use (like here in this matter witch he lost his machine by only changing DNS settings). Plus having Webmin in a server is a nonsense in a security matter (like having a bunker with a wood door). You have everything to gain by learning the linux administration witch covers webmin. –  Antoine Rodriguez Oct 22 '12 at 17:53
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I think you should not use addresses out of range: address 10.100.200.300 is not valid, every octet can be in range 0 to 255 only.

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The problem you are having is that 300 is not a valid number. You must use 0 though 255 in each of the four "octets". Also, by using 10.100.200.# you are probably on a different network that your client device.

You need to take a look at what the ip address and subnet mask on your client machine is. This should let you know what a usable address on this network should look like.

Without going into a full TCP/IP class, if your subnet mask is 255.255.255.0 then the first three "octets" should match. For example:

Client IP address: 10.0.10.5
Client Subnet Mask: 255.255.255.0

The Server should have an IP address of 10.0.10.1 through 10.0.10.254, with a subnet mask of 255.255.255.0. You would also want to check your router to make sure you don't create an IP address conflict by assigning an address that's already been assigned.

Also, you said you changed the DNS address. Do you mean you changed the IP address? Or, did you actually change the DNS address? If you changed the DNS address, what was the previous IP address you accessed the server with? Try the "old" IP address when you ping and SSH, and let me know what your results were.

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No idea why this was voted down. –  belacqua Jun 7 '13 at 17:31
    
Because another user had a strong opinion about the use of webmin as an administrative tool. –  Argusvision Jun 10 '13 at 15:22
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Webmin is a great tool, if you know what you're doing. It's a handy way to manage one, or many linux boxes without having to know how to format and where each config file is. It's a powerful tool for system administration.

Like any tool, if you don't know how to use it, you're going to muck things up, and because it's meant for server administration, you can muck things up badly, quickly.

With that said, when used correctly, webmin can reduce the time you spend doing redundant tasks, and can help you quickly find and change a configuration. I manage 20-30 linux servers and VM's, I understand the command line, the configuration files, and how to manage a server. I have webmin installed on all our linux servers, (no gui on any of them).

It's not reasonable to bash a tool because someone isn't using it correctly, or simply doesn't know how to use it. It is valuable to understand basic networking before conquering DNS, but it's commendable that people are trying, asking, researching, and correcting their errors.

Isn't that how we all learned this stuff.

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