system toolbox » ubuntu

dev-infra-2:/etc/ssh/sshd_config

X11Forwarding yes
X11DisplayOffset 10
#X11UseLocalhost no

root@dev-infra-2:~# xclock

Error: Can't open display: localhost:10.0

http://csociety.ecn.purdue.edu/~sigos/projects/ssh/forwarding/

Automagic X11 forwarding¶

SSH will, by default, automatically set up X11 forwarding for you if you run the ssh client with your $DISPLAY environment variable set (i.e. if you are using X11). You can turn off this behaviour with command line switches as well as with the config file in your $HOME/.ssh directory. For most users, this is enough; it works quite transparently.

Underlying mechanism¶

SSH does several things to facilitate "more secure" X11 forwarding. I try to use the terms "ssh client", "ssh server", "X client", and "X server" in this section to help clarify things. Remember that the X server is the program that runs on your display and puts things into your framebuffer; the X clients are the programs (like xterm, fvwm, netscape) that connect to your display to tell it what to draw where. When you are using ssh and X11 you are usually running the ssh client on the same machine that the X server is running on (the machine you are sitting in front of), and the ssh server is running on the remote system, and you are running some X clients on the remote system and the ssh server is forwarding them to the ssh client which is forwarding them to the X server. Whew.

• Forwarding traffic.

SSH will allocate a "fake" display on the remote system and attach a "dummy" X server to it. It forwards traffic sent to the fake display through the *encrypted tunne*l. On the other end, it then gets sent to whatever display your $DISPLAY variable pointed to on the ssh client system.

SSH will automatically set your DISPLAY variable on the remote system to the "fake" server.

...

trebamo li xserver-xorg na remote strani ?¶

ne trebamo, očeivano:

root@dosbox:~# apt-get remove xserver-xorg

i nakon toga stvar radi ...

hernad@nmraka-1:~$ ssh -Y -C -v fmk@dosbox.sigma-com.net

OpenSSH_4.7p1 Debian-8ubuntu1.2, OpenSSL 0.9.8g 19 Oct 2007
debug1: Reading configuration data /home/hernad/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to dosbox.sigma-com.net [192.168.45.183] port 22.
debug1: Connection established.
debug1: identity file /home/hernad/.ssh/git-b-out-ba type 1
debug1: identity file /home/hernad/.ssh/identity type 0
debug1: identity file /home/hernad/.ssh/id_rsa type 1
debug1: identity file /home/hernad/.ssh/id_dsa type 2
debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3p2 Debian-8ubuntu1
debug1: match: OpenSSH_4.3p2 Debian-8ubuntu1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_4.7p1 Debian-8ubuntu1.2
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-cbc hmac-md5 zlib@openssh.com
debug1: kex: client->server aes128-cbc hmac-md5 zlib@openssh.com
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'dosbox.sigma-com.net' is known and matches the RSA host key.
debug1: Found key in /home/hernad/.ssh/known_hosts:31
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: /home/hernad/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: /home/hernad/.ssh/id_dsa
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: /home/hernad/.ssh/git-b-out-ba
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: password
fmk@dosbox.sigma-com.net's password: 
debug1: Enabling compression at level 6.   <<<<<<<<<<<<<<<<<<<<<<<<<<<<
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: Requesting X11 forwarding with authentication spoofing. <<<<<<<<<<<<<<<
debug1: Sending environment.
debug1: Sending env LANG = bs_BA.UTF-8
Linux dosbox.sigma-com.net 2.6.18-053.6hernad3-openvz #1 SMP Sat Feb 16 15:59:27 CET 2008 i686
...

na dosbox.sigma-com.net radi

$ xclock

radi i kada se prijavim kao root i kao fmk

hah ...

kada sam podesio
/etc/hosts

127.0.0.1 localhost.localdomain localhost

root@dev-infra-2:~# ping localhost

PING localhost.localdomain (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=1 ttl=64 time=0.028 ms

stvar radi ko melčin horoz