ssh-copy-id命令详解 & 使用ssh-keygen和ssh-copy-id三步实现SSH无密码登录

http://blog.csdn.net/john_f_lau/article/details/22303341

http://blog.chinaunix.net/uid-26284395-id-2949145.html

ssh-copy-id命令可以把本地的ssh公钥文件安装到远程主机对应的账户下。                                                                                                          
达到的功能:
       ssh-copy-id - 将你的公共密钥填充到一个远程机器上的authorized_keys文件中。
 
使用模式:
       ssh-copy-id [-i [identity_file]] [user@]machine
 
描述:  
       ssh-copy-id 是一个实用ssh去登陆到远程服务器的脚本(假设使用一个登陆密码,
                   因此,密码认证应该被激活直到你已经清理了做了多个身份的使用)。
                   它也能够改变远程用户名的权限,~/.ssh和~/.ssh/authorized_keys
                   删除群组写的权限(在其它方面,如果远程机上的sshd在它的配置
                   文件中是严格模式的话,这能够阻止你登陆。)。

 
                   如果这个 “-i”选项已经给出了,然后这个认证文件(默认是~/.ssh
                   /id_rsa.pub)被使用,不管在你的ssh-agent那里是否有任何密钥。


                   另外,命令 “ssh-add -L” 提供任何输出,它使用这个输出优先于
                   身份认证文件。如果给出了参数“-i”选项,或者ssh-add不产生输出,
                   然后它使用身份认证文件的内容。一旦它有一个或者多个指纹,它使
                   用ssh将这些指纹填充到远程机~/.ssh/authorized_keys文件中。


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
  1. jsmith@local-host$ [Note: You are on local-host here]
  2. jsmith@local-host$ ssh-keygen
  3. Generating public/private rsa key pair.
  4. Enter file in which to save the key (/home/jsmith/.ssh/id_rsa):[Enter key]
  5. Enter passphrase (empty for no passphrase): [Press enter key]
  6. Enter same passphrase again: [Pess enter key]
  7. Your identification has been saved in /home/jsmith/.ssh/id_rsa.
  8. Your public key has been saved in /home/jsmith/.ssh/id_rsa.pub.
  9. The key fingerprint is:
  10. 33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9 jsmith@local-host
第二步:用ssh-copy-id将公钥复制到远程机器中
  1. jsmith@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
  2. jsmith@remote-host's password:
  3. Now try logging into the machine, with "ssh 'remote-host'", and check in:
  4. .ssh/authorized_keys
  5. to make sure we haven't added extra keys that you weren't expecting.

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
  1. jsmith@local-host$ ssh remote-host
  2. Last login: Sun Nov 16 17:22:33 2008 from 192.168.1.2
  3. [Note: SSH did not ask for password.]
  4. jsmith@remote-host$ [Note: You are on remote-host here]

 

常见问题:

  1. 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

[1]

  1. /usr/bin/ssh-copy-id: ERROR: No identities found

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)

 

  1. jsmith@local-host$ ssh-agent $SHELL
  2. jsmith@local-host$ ssh-add -L
  3. The agent has no identities.
  4. jsmith@local-host$ ssh-add
  5. Identity added: /home/jsmith/.ssh/id_rsa (/home/jsmith/.ssh/id_rsa)
  6. jsmith@local-host$ ssh-add -L
  7. ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAsJIEILxftj8aSxMa3d8t6JvM79DyBV
  8. aHrtPhTYpq7kIEMUNzApnyxsHpH1tQ/Ow== /home/jsmith/.ssh/id_rsa
  9. jsmith@local-host$ ssh-copy-id -i remote-host
  10. jsmith@remote-host's password:
  11. Now try logging into the machine, with "ssh 'remote-host'", and check in:
  12. .ssh/authorized_keys
  13. to make sure we haven't added extra keys that you weren't expecting.
  14. [Note: This has added the key displayed by ssh-add -L]

[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.

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