ssh-keygen 产生公钥与私钥对.
ssh-copy-id 将本机的公钥复制到远程机器的authorized_keys文件中，ssh-copy-id也能让你有到远程机器的home, ~./ssh , 和 ~/.ssh/authorized_keys的权利
第一步:在本地机器上使用ssh-keygen产生公钥私钥对
jsmith@local-host$ ssh-keygen
第二步:用ssh-copy-id将公钥复制到远程机器中
jsmith@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
注意: ssh-copy-id将key写到远程机器的~/ .ssh/authorized_key.文件中
第三步: 登录到远程机器不用输入密码
jsmith@local-host$ ssh remote-host
常见问题：
ssh-copy-id -u eucalyptus -i ~eucalyptus/.ssh/id_rsa.pub eucalyptus@remote_host
上述是给eucalyptus用户赋予无密码登陆的权利
使用选项 -i ，当没有值传递的时候或者 如果 ~/.ssh/identity.pub 文件不可访问（不存在）, ssh-copy-id 将显示上述的错误信息 （ -i选项会优先使用将ssh-add -L的内容）
jsmith@local-host$ ssh-agent $SHELL
jsmith@local-host$ ssh-add -L
jsmith@local-host$ ssh-add
jsmith@local-host$ ssh-add -L
jsmith@local-host$ ssh-copy-id -i remote-host
ssh-copy-id应注意的三个小地方
Default public key: ssh-copy-id uses ~/.ssh/identity.pub as the default public key file (i.e when no value is passed to option -i). Instead, I wish it uses id_dsa.pub, or id_rsa.pub, or identity.pub as default keys. i.e If any one of them exist, it should copy that to the remote-host. If two or three of them exist, it should copy identity.pub as default.
The agent has no identities: When the ssh-agent is running and the ssh-add -L returns “The agent has no identities” (i.e no keys are added to the ssh-agent), the ssh-copy-id will still copy the message “The agent has no identities” to the remote-host’s authorized_keys entry.
Duplicate entry in authorized_keys: I wish ssh-copy-id validates duplicate entry on the remote-host’s authorized_keys. If you execute ssh-copy-id multiple times on the local-host, it will keep appending the same key on the remote-host’s authorized_keys file without checking for duplicates. Even with duplicate entries everything works as expected. But, I would like to have my authorized_keys file clutter free.
