【转】使用ssh-keygen和ssh-copy-id三步实现SSH无密码登录

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

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：

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]

/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

1. 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.