Error logging in via ssh?

Question

linux

When connecting via ssh from centos to centos, authorization fails,
# ssh -v [email protected]
OpenSSH_5.3p1, OpenSSL 1.0.1k 8 Jan 2015
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 10.xx.yy.21 [10.xx.yy.21] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/identity-cert type -1
debug1: identity file /root/.ssh/id_rsa type - 1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1 debug1: identity file /root/.ssh/id_ecdsa type -1 debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
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
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '10.xx.yy.21' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:41 debug1 :
ssh_rsa_verify: signature correct debug1
: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS -keyex,gssapi-with-mic debug1: Next authentication method: gssapi-keyex debug1: No valid Key exchange context debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Cannot determine realm for numeric host address
debug1: Unspecified GSS failure. Minor code may provide more information
Cannot determine realm for numeric host address
debug1: Unspecified GSS failure. Minor code may provide more information
debug1: Unspecified GSS failure. Minor code may provide more information
Cannot determine realm for numeric host address
debug1: Next authentication method: publickey
debug1: Trying private key: /root/.ssh/identity
debug1: Trying private key: /root/.ssh/id_rsa
debug1: Trying private key: /root/.ssh/id_dsa
debug1: Trying private key: /root/.ssh/id_ecdsa How to fix the situation and finally connect to the server?
debug1: No more authentication methods to try.
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

Answer 1

# ssh -v [email protected]

Very often (and very correctly!) SSH connection is prohibited by configurations for root:
Can't ssh in as root with password

Answer 2

Try specifying the keys you need manually. ssh -i /root/.ssh/id_dsa -v [email protected]
I remember exactly the situation in my practice when I could not connect due to a large number of keys.
And yes, quite possibly a lot more useful information can be found in the server's sshd log.