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i have the root password for a machine in the lab. the ssh service has been stopped on the machine. is it possible to login to the machine. this is not for doing any damage. i have physical access to the machine. just to test if it is possible.

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up vote 1 down vote accepted

X windows is running
how do i use x server to log on to that machine.

There's only a very small chance you can. Just running X is not enough; it also needs to have been configured to allow remote login (such as XDMCP). And any firewall or router needs to have the ports configured well (TCP 6000-6005 for X11, UDP 177 for XDMCP, and optionally TCP 7100 for the xfs font server), for otherwise it will only work using ssh -Y after all. A sane administrator would probably only allow access through SSH anyway.

But, you could try Xephyr (or the older Xnest, or XWin.exe in Cygwin), using something like:

Xephyr :1 -query name-or-ip-of-remote-machine
XWin.exe -query name-or-ip-of-remote-machine

As you actually do have physical access, you might be able to set up the machine to your needs, but I assume setting up some VCN to some existing GNOME or KDE session is easier. Or set up something like monit to auto restart SSH when it dies. (See Monit: Monitor SSHD Server and Auto Restart SSH If It Does Not Respond, and to install use something like sudo apt-get install monit if applicable.)

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i get it now. i have to physically make some changes to the machine. if telnet, xdmcp etc are not configured. – Rohit Banga Oct 13 '09 at 10:35
Yes, or better yet, make SSH auto-restart using monit: – Arjan Oct 13 '09 at 10:42

When a service is "stopped", it does mean that "it doesn't run".

So except if you have another application that can be used to login (telnet, X Windows, rsh) you will have to go in front of the screen/console and start the service (or ask someone to do it for you).

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X windows is running – Rohit Banga Oct 13 '09 at 9:29
how do i use x server to log on to that machine. – Rohit Banga Oct 13 '09 at 9:34

Yes, If telnet is there, its possible to login to that box using it even when ssh is not available. Try using putty to connect using telnet. The default port for telent is 23. If you use putty, it will show default ports whenever you select an option.

If telnet is not there, you can see if rlogin is there. The default port to connect to is 513. The remote machine should be running a rlogind daemon for this to work.

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what port should i connect to? – Rohit Banga Oct 13 '09 at 9:17
i am on a linux machine, but putty is for windows. – Rohit Banga Oct 13 '09 at 9:21
it is 23. check my edited answer – vpram86 Oct 13 '09 at 9:21
putty is there for both. For unix you need to build from source. Please check the link i mentioned in the answer – vpram86 Oct 13 '09 at 9:22
telnet is not running on that machine. – Rohit Banga Oct 13 '09 at 9:22

Other login possibilities include:

  • telnet
  • rsh
  • rdesktop
  • xrdp
  • vnc

Another possibility is to use ftp. It can be tedious, but if you can manipulate the filesystem, you might fix the problem.

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If you can't figure how to log into the x server type ctrl-alt-f1 and log into the console there

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there i get the localhost login prompt. when i try root@ipaddress and password, it says login incorrect. – Rohit Banga Oct 13 '09 at 10:22
Ctrl-Alt-F1 on the remote machine, that is, to which you have physical access. So, no "@.." part. – Arjan Oct 13 '09 at 10:32

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