I am new to LINUX/UNIX administration task. My Infrastructure admin has allocated me a special lab server in client location. Per my requirement, had chanted few settings in LINUX/UNIX and need to reboot the server. I am the "root" user. I had used "shutdown -r now" at command line prompt from my PuTTy application. Suddently was closed my PuTTy application with connection refuse.
Now I want to connect my Lab server with root as user. When I am trying to connecting from PuTTy and it was still giving as "Network connection refuse". Please help me how to I connect successfully.
Apparently you changed something that prevents the server from starting again. If it's a physical server, there might be an ILOM/iLO access available. For a virtual machine, there should be a similar way to get a virtual console.
As for the disconnect: PuTTY is a client for the SSH protocol. As soon as the servers SSH daemon is down (which happens during a shutdown) the connection is dropped. Similar to a RDP connection, which is dropped when the Windows host is shutting down. Connections can only be established again when both the network and the daemon are up again.