I am using Ubuntu 10.04 Lucid Lynx. I have installed openssh-server. When I try to connect to remote systems I get a message as "could not resolve hostname : Name or server not known" What does it mean. What should I do?
Thanks in advance..

In a website it was told as..
ssh -vv username@hostname ... for providing verbose information of what my problem is while connecting through ssh server. I got ..

OpenSSH_5.3p1 Debian-3ubuntu6, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
ssh: Could not resolve hostname linux-desktop: Name or service not known

What does this mean? Please do help me..

DNS not working or you misspelled host name. If you known IP of this host connect by it. Can you post your command line?

"linux-desktop" is not your hostname. Check it by command:Please do not start the same thread more then once. Edit ealier post.

Thanks for reply..

linux@linux-laptop:~$ ssh linux@linux-desktop
ssh: Could not resolve hostname linux-desktop: Name or service not known

This is what I get. How to check if DNS is working? How to make it work if it doesnt?

If I want to connect to other system in remote administration I use ssh command.
ssh username@hostname
In this:
username : other system's username
hostname : other system's hostname
Is this the way I have to do?

Threads have been merged. Please, don't double post: in order to receive more and quick help, it's better to keep discussion in one place. Thanks.

If you just want to connect back to your own host, try
ssh username@127.0.0.1
where you replace username with the name of the account you want to land in.

If the machine you want to connect to is NOT your local machine, replace the 127.0.0.1 with the IP address of the target machine.

For more lasting solutions, you might want to ensure that all machines on your local domain are well formed and unique, load up a proper hosts file with their addresses and names, then install and run DNSMASQ. The default configuration will load that hosts file and provide DNS services to resolve those names. Make sure you set it to forward requests it cannot satisfy to your ISP DNS servers. From that point you can set it as a nameserver for itself and all other machines and names will resolve properly on your local network.

I want to connect to other machine (eg: a.b.c.d with a username of that machine as linux)
ssh linux@a.b.c.d
If I give like this I get as "could not resolve IPaddress a.b.c.d: Name or sever not known"
What should I do in this case?
Is there any installation I must do?
Should I set a publickey and change my port number?
What should I do?
Please do help me...

This is not a problem with installation, public keys nor port numbers. Please post your real command line not an example, as message is clear - "Name of server is not known".

1 members found this post helpful.

as eSelix says, please post the actual command you use. This means copy and paste from your terminal into your post.
and enclose it in code tags so it's clear which command you typed and the result it gave.

also, to debug this problem which seems to be a name resolution issue, please try pinging your machine

linux@linux-laptop:~$ ssh linux@linux-desktop
ssh: Could not resolve hostname linux-desktop: Name or service not known
linux@linux-laptop:~$ ssh linux@59.96.117.135
ssh: connect to host 59.96.117.135 port 22: Connection timed out
linux@linux-laptop:~$

I have copied my terminal as you have asked.
What changes should I do to establish the connection?

few basic troubleshooting:-
1. check your "/etc/resolv.conf" to see whether it has proper dns server entries.
2. try "telnet remote-host-IP 22" to see whether port 22 (ssh) is running there. if it works then it is problem with your DNS server.
3. try "host remote-host" to see if dns is resolving correctly.

Is SSH running on 59.96.117.135? To start ssh the command is: sudo /etc/init.d/ssh start
Is a firewall is running on that computer? If so is it configured to allow ssh?