ssh-copy-id命令的介绍，使免密更方便

ssh-copy-id命令的介绍，使免密更方便

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

jsmith@local-host$ [Note: You are on local-host here]
jsmith@local-host$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/jsmith/.ssh/id_rsa):[Enter key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Pess enter key]
Your identification has been saved in /home/jsmith/.ssh/id_rsa.
Your public key has been saved in /home/jsmith/.ssh/id_rsa.pub.
The key fingerprint is:
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

jsmith@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
jsmith@remote-host's password:
Now try logging into the machine, with "ssh 'remote-host'", and check in:
.ssh/authorized_keys
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

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

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

/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）

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

[2] 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.