在使用ssh-copy-id命令时，出现了如下错误：
# ssh-copy-id -i id_rsa.pub kiwenlau@136.187.59.2
/usr/bin/ssh-copy-id: ERROR: failed to open ID file './id_rsa': No such file
命令的输出信息提示没有私钥"id_rsa"文件。可知，ssh-copy-id命令执行时将检查公钥id_rsa.pub所在目录是否存在私钥id_rsa，若没有私钥则会导致命令执行失败。
这个问题的解决办法很简单，使用touch命令在公钥id_rsa.pub所在目录下创建一个空文件“id_rsa”即可。
# touch id_rsa
然后ssh-copy-id命令就可以执行成功了。
# ssh-copy-id -i id_rsa.pub kiwenlau@192.168.59.2
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'kiwenlau@192.168.59.2'"
and check to make sure that only the key(s) you wanted were added.
这时，使用ssh登录远程主机将不需要输入密码。
# ssh kiwenlau@192.168.59.2
Welcome to Ubuntu 14.04.2 LTS (GNU/Linux 3.13.0-32-generic x86_64)
* Documentation:
System information as of Sat Jun 20 15:39:25 JST 2015
System load: 0.0 Processes: 93
Usage of /: 13.0% of 17.34GB Users logged in: 1
Memory usage: 22% IP address for eth0: 192.168.59.2
Swap usage: 0% IP address for docker0: 172.17.42.1
Graph this data and manage this system at:
22 packages can be updated.
2 updates are security updates.
Last login: Sat Jun 20 15:39:25 2015 from 192.168.59.3