If your server is Windows-based then the console shell can help you diagnose and fix it, even if the system hasn’t started pinging or responding to remote desktop connections yet.
Once you have connected to the console and seen that the server is trying to boot from the local disc, you should see the Windows boot menu, followed almost immediately by the Special Administration Console which looks like this:
Computer is booting, SAC started and initialized. Use the "ch -?" command for information about using channels. Use the "?" command for general help. SAC> EVENT: The CMD command is now available. SAC>
help will reveal the list of commands, which is limited largely to helping you kill runaway processes, or resetting the system’s IP address.
ch Channel management commands. Use ch -? for more help. cmd Create a Command Prompt channel. d Dump the current kernel log. f Toggle detailed or abbreviated tlist info. ? or help Display this list. i List all IP network numbers and their IP addresses. i <#> <ip> <subnet> <gateway> Set IPv4 addr., subnet and gateway. id Display the computer identification information. k <pid> Kill the given process. l <pid> Lower the priority of a process to the lowest possible. lock Lock access to Command Prompt channels. m <pid> <MB-allow> Limit the memory usage of a process to <MB-allow>. p Toggle paging the display. r <pid> Raise the priority of a process by one. s Display the current time and date (24 hour clock used). s mm/dd/yyyy hh:mm Set the current time and date (24 hour clock used). t Tlist. restart Restart the system immediately. shutdown Shutdown the system immediately. crashdump Crash the system. You must have crash dump enabled.
If you need to do more than this, you will need to ask for a command prompt, a function which is only available a little later in the boot process (the SAC will usually confirm within 20-40s). You just need to type
cmd then press Esc twice. You will be asked to authenticate and then be presented with a command prompt.
Microsoft Windows [Version 6.0.6002] Copyright (c) 2006 Microsoft Corporation. All rights reserved. C:\Windows\system32>
You can use the command prompt to do more involved maintenance such as using netsh to disable the firewall or rearrange routing information, or net stop to stop problematic services.