I have built a two machine (4 core/8GB, 8 Core/16GB) with the latest Red Hat Linux. I've already installed standalone copies of Hadoop and both machine work just fine. But in setting up the hive I have to get public keys without password working between the machines. They are called GRID1 and GRID3. GRID3 will be the master and GRID1 the slave. Both have a group setup as hadoop and a user as hduser.

GRID3 Activity:
Logon as hduser
ssh-keygen -t rsa -P ""
cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys
copy authorized_keys over to GRID1:/home/hduser/.ssh/
ssh localhost - ok

[hduser@grid3 ~]$ ssh 'hduser@grid1'
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
[hduser@grid3 ~]$

[hduser@grid3 ~]$ ssh 'hduser@grid1'
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
[hduser@grid3 ~]$

/etc/ssh/sshd_config
PasswordAuthentication no

So I seem to be having Public Key problems

Assuming the key files are in the right places, it's likely a permissions issue. chmod the public and private key files to 400.

You can always try "ssh -vv" from the client side as well as looking at /var/log/secure on the server side to get a better idea of what's causing it to fail.

First I checked the client for permissions reset to 400

[hduser@grid3 ssh]$ cl
-bash: cl: command not found
[hduser@grid3 ssh]$ ssh -vv hduser@grid1
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to grid1 [192.168.2.203] port 22.
debug1: Connection established.
debug1: identity file /home/hduser/.ssh/identity type 0
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug2: key_type_from_name: unknown key type '-----END'
debug1: identity file /home/hduser/.ssh/id_rsa type 1
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug2: key_type_from_name: unknown key type 'Proc-Type:'
debug2: key_type_from_name: unknown key type 'DEK-Info:'
debug2: key_type_from_name: unknown key type '-----END'
debug1: identity file /home/hduser/.ssh/id_dsa type 2
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
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
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
debug2: dh_gen_key: priv key bits set: 131/256
debug2: bits set: 514/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'grid1' is known and matches the RSA host key.
debug1: Found key in /home/hduser/.ssh/known_hosts:1
debug2: bits set: 492/1024
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
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/hduser/.ssh/id_rsa (0x7f56b7e3aa70)
debug2: key: /home/hduser/.ssh/id_dsa (0x7f56b7e3b300)
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug2: we did not send a packet, disable method
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure. Minor code may provide more information
Credentials cache file '/tmp/krb5cc_502' not found

debug1: Unspecified GSS failure. Minor code may provide more information
Credentials cache file '/tmp/krb5cc_502' not found

debug1: Unspecified GSS failure. Minor code may provide more information


debug1: Unspecified GSS failure. Minor code may provide more information


debug2: we did not send a packet, disable method
debug1: Next authentication method: publickey
debug1: Offering public key: /home/hduser/.ssh/id_rsa
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug1: Offering public key: /home/hduser/.ssh/id_dsa
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
[hduser@grid3 ssh]$


the log on the server states:

bad ownership or modes for directory /home/hduser/.ssh

hduser:hadoop
600

authentication_keys
hduser:hadoop
400

I think I fixed it

chmod go-w ~/
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys