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mahmoodn 05-23-2011 02:45 AM
Can't open display
 
I remember that I could forward x11 from a remote server. but I don't know what happened that no longer I can forward x11.

I use "ssh -X server_ip" and when I run "xlock" it says:
Code:
Error: Can't open display:
any idea about that?

adamk75 05-23-2011 04:25 AM
Is X11 forwarding enabled on the ssh server?

Adam

mahmoodn 05-23-2011 04:27 AM
yes
Code:
mahmood@mpc:~$ cat /etc/ssh/sshd_config | grep "X11*"
X11Forwarding yes
X11DisplayOffset 10

adamk75 05-23-2011 04:49 AM
Then run both the server and client in verbose/debug mode and see what messages are produced.

Adam

mahmoodn 05-23-2011 04:59 AM
From client->server
Code:

mahmood@myhost:~$ ssh -vvv -X mpc
OpenSSH_5.3p1 Debian-3ubuntu5, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to mpc [195.179.69.105] port 22.
debug1: Connection established.
debug1: identity file /home/mahmood/.ssh/identity type -1
debug1: identity file /home/mahmood/.ssh/id_rsa type -1
debug1: identity file /home/mahmood/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3p1 Debian-3ubuntu6
debug1: match: OpenSSH_5.3p1 Debian-3ubuntu6 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu5
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug3: Wrote 792 bytes for a total of 831
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug3: Wrote 24 bytes for a total of 855
debug2: dh_gen_key: priv key bits set: 135/256
debug2: bits set: 512/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: Wrote 144 bytes for a total of 999
debug3: check_host_in_hostfile: filename /home/mahmood/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 28
debug3: check_host_in_hostfile: filename /home/mahmood/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 27
debug1: Host 'mpc' is known and matches the RSA host key.
debug1: Found key in /home/mahmood/.ssh/known_hosts:28
debug2: bits set: 500/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: Wrote 16 bytes for a total of 1015
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug3: Wrote 48 bytes for a total of 1063
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/mahmood/.ssh/identity ((nil))
debug2: key: /home/mahmood/.ssh/id_rsa ((nil))
debug2: key: /home/mahmood/.ssh/id_dsa ((nil))
debug3: Wrote 64 bytes for a total of 1127
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred gssapi-keyex,gssapi-with-mic,gssapi,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/mahmood/.ssh/identity
debug3: no such identity: /home/mahmood/.ssh/identity
debug1: Trying private key: /home/mahmood/.ssh/id_rsa
debug3: no such identity: /home/mahmood/.ssh/id_rsa
debug1: Trying private key: /home/mahmood/.ssh/id_dsa
debug3: no such identity: /home/mahmood/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
mahmood@mpc's password:
debug3: packet_send2: adding 64 (len 56 padlen 8 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug3: Wrote 144 bytes for a total of 1271
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug3: Wrote 128 bytes for a total of 1399
debug2: callback start
debug2: x11_get_proto: /usr/bin/xauth  list :1.0 2>/dev/null
debug1: Requesting X11 forwarding with authentication spoofing.
debug2: channel 0: request x11-req confirm 0
debug3: Wrote 112 bytes for a total of 1511
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug1: Sending environment.
debug3: Ignored env ORBIT_SOCKETDIR
debug3: Ignored env SSH_AGENT_PID
debug3: Ignored env CKPTDIR
debug3: Ignored env TERM
debug3: Ignored env SHELL
debug3: Ignored env XDG_SESSION_COOKIE
debug3: Ignored env WINDOWID
debug3: Ignored env SCRIPT_ROOT
debug3: Ignored env GNOME_KEYRING_CONTROL
debug3: Ignored env GTK_MODULES
debug3: Ignored env USER
debug3: Ignored env STAT_DIR
debug3: Ignored env LS_COLORS
debug3: Ignored env SSH_AUTH_SOCK
debug3: Ignored env DEFAULTS_PATH
debug3: Ignored env SESSION_MANAGER
debug3: Ignored env USERNAME
debug3: Ignored env XDG_CONFIG_DIRS
debug3: Ignored env DESKTOP_SESSION
debug3: Ignored env PATH
debug3: Ignored env FLEXUS_ROOT
debug3: Ignored env PWD
debug3: Ignored env GDM_KEYBOARD_LAYOUT
debug1: Sending env LANG = en_US.utf8
debug2: channel 0: request env confirm 0
debug3: Ignored env GNOME_KEYRING_PID
debug3: Ignored env MANDATORY_PATH
debug3: Ignored env GDM_LANG
debug3: Ignored env SIMICS_ROOT
debug3: Ignored env GDMSESSION
debug3: Ignored env SPEECHD_PORT
debug3: Ignored env SHLVL
debug3: Ignored env HOME
debug3: Ignored env GNOME_DESKTOP_SESSION_ID
debug3: Ignored env LOGNAME
debug3: Ignored env BOOST_ROOT
debug3: Ignored env XDG_DATA_DIRS
debug3: Ignored env DBUS_SESSION_BUS_ADDRESS
debug3: Ignored env LESSOPEN
debug3: Ignored env DISPLAY
debug3: Ignored env LESSCLOSE
debug3: Ignored env XAUTHORITY
debug3: Ignored env COLORTERM
debug3: Ignored env _
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug3: Wrote 448 bytes for a total of 1959
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Linux mpc 2.6.32-24-server #39-Ubuntu SMP Wed Jul 28 06:21:40 UTC 2010 x86_64 GNU/Linux
Ubuntu 10.04.1 LTS

....
mahmood@mpc:~$
But I don't know what do you mean by verbose on server side

mahmoodn 05-24-2011 03:37 AM
Well I found the solution here
quoting from Andreas Steinel (Message #20)
Code:
1) Adding the following to your sshd_config
AddressFamily inet
2) Restart SSH

Afterwards, the SSH daemon is able to create the X11 socket and
X-Forwarding works as expected.


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