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Thread: SSH login very slow - after login is fast

  1. #1
    Join Date
    Aug 2005
    Location
    Rio de Janeiro, Brasil
    Beans
    91

    SSH login very slow - after login is fast

    Hi folks, on a particular Ubuntu 8.04 server, ssh is very slow at login. Digging around, I comment the following parameters on ssh_config.conf

    #SSAPIAuthentication yes
    #GSSAPIDelegateCredentials no

    But it didn't work either. Here is a debug session:

    supervisor@linux02:/srv$ ssh -C -v fabricio@192.168.0.6
    OpenSSH_5.3p1 Debian-3ubuntu5, OpenSSL 0.9.8k 25 Mar 2009
    debug1: Reading configuration data /etc/ssh/ssh_config
    debug1: Applying options for *
    debug1: Connecting to 192.168.0.6 [192.168.0.6] port 22.
    debug1: Connection established.
    debug1: identity file /home/supervisor/.ssh/identity type -1
    debug1: identity file /home/supervisor/.ssh/id_rsa type -1
    debug1: identity file /home/supervisor/.ssh/id_dsa type -1
    debug1: Remote protocol version 2.0, remote software version OpenSSH_4.7p1 Debian-8ubuntu1
    debug1: match: OpenSSH_4.7p1 Debian-8ubuntu1 pat OpenSSH_4*
    debug1: Enabling compatibility mode for protocol 2.0
    debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu5
    debug1: SSH2_MSG_KEXINIT sent
    debug1: SSH2_MSG_KEXINIT received
    debug1: kex: server->client aes128-ctr hmac-md5 zlib@openssh.com
    debug1: kex: client->server aes128-ctr 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 '192.168.0.6' is known and matches the RSA host key.
    debug1: Found key in /home/supervisor/.ssh/known_hosts:2
    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

    --- Here it takes almost one minute...

    debug1: Authentications that can continue: publickey,password
    debug1: Next authentication method: publickey
    debug1: Trying private key: /home/supervisor/.ssh/identity
    debug1: Trying private key: /home/supervisor/.ssh/id_rsa
    debug1: Trying private key: /home/supervisor/.ssh/id_dsa
    debug1: Next authentication method: password

    Does anybody have any glue?

    Thanks in advance,
    Josir Gomes

  2. #2
    Join Date
    Aug 2005
    Beans
    82

    Re: SSH login very slow - after login is fast

    Did you ever fix this problem Josir?

  3. #3
    Join Date
    Aug 2005
    Location
    Rio de Janeiro, Brasil
    Beans
    91

    Re: SSH login very slow - after login is fast

    Yes!

    Just add the parameter "UseDNS no" on

    /etc/ssh/sshd_config

    Good Luck.
    Josir

  4. #4
    Join Date
    Oct 2009
    Beans
    Hidden!
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: SSH login very slow - after login is fast

    Guess it was doing a reverse DNS lookup.

    Code:
         UseDNS  Specifies whether sshd(8) should look up the remote host name and
                 check that the resolved host name for the remote IP address maps
                 back to the very same IP address.  The default is ``yes''.
    In any case, here is what that option does.
    Come to #ubuntuforums! We have cookies! | Basic Ubuntu Security Guide

    Tomorrow's an illusion and yesterday's a dream, today is a solution...

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