[转] Linux服务器三步骤配置免密码登陆

注意: ssh-copy-id 将key写到远程机器的 ~/ .ssh/authorized_key.文件中

常见问题：

上述是给eucalyptus用户赋予无密码登陆的权利

[1] 

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）

[2] ssh-copy-id应注意的三个小地方

1. 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.
2. 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.
3. 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.