安装greenplum数据库进行交换密码时输入root的密码一直不成功，后
用 gpssh-exkeys -f hostfile_exkeys 命令结果如下：
[STEP 1 of 5] create local ID and authorize on local host
… /root/.ssh/id_rsa file exists … key generation skipped
[STEP 2 of 5] keyscan all hosts and update known_hosts file
[STEP 3 of 5] authorize current user on remote hosts
… send to sdw1
Enter password for sdw1:
[ERROR sdw1] Incompatible ssh peer (no acceptable kex algorithm)
这是由于ssh 6.7以上屏蔽不安全算法，在/etc/ssh/sshd_config最后加上
KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
重启ssh服务，问题解决。
参考：http://blog.csdn.net/coder_xia/article/details/50382278
