I got two computers with the exact same symptoms today: Both seem to be alive. They answer pings and they host virtual machines which are working.
However, I cannot login via SSH. I get
$ ssh -v obelix OpenSSH_5.3p1 Debian-3ubuntu6, OpenSSL 0.9.8k 25 Mar 2009 debug1: Reading configuration data /home/mike/.ssh/config debug1: Applying options for obelix debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to obelix [10.10.11.238] port 22. debug1: Connection established. debug1: identity file /home/mike/.ssh/id_rsa type 1 debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048 debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048 ssh_exchange_identification: Connection closed by remote host
On the console I can switch the ttys and enter my login credentials. After that I see the GNU/Debian Linux welcome message an no prompt. The system seems to hang. I'm able to switch the tty again and login with the same result. (I tried that three times now and I start running out of ttys.)
A search on the Internet suggested some ressoucre shortage.
How could I release some resoucres than?
How could I further investigate the situation before just trying a hard power off?
(Currently I don't even know how to reboot the system gracefully.)