How to configure password-free ssh for linux remote login
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I. Scenario
The company has just installed a few linux, and now it is necessary to remotely ssh password-free login between hosts.
II. Principle
Very simple, use ssh-keygen to generate private and public keys on host a, copy the generated public key to remote host b, and then use ssh command to log in to another host b without password.
III. Steps
Host a:
1. Generate public key and private key files id_rsa and id_rsa.pub (type 3 and enter)
[root@bogon ~]# ssh-keygen -t rsa
generating public/private rsa key pair.
enter file in which to save the key (/root/.ssh/id_rsa):
enter passphrase (empty for no passphrase):
enter same passphrase again:
your identification has been saved in /root/.ssh/id_rsa.
your public key has been saved in /root/.ssh/id_rsa.pub.
the key fingerprint is:
67:da:0d:79:e0:d6:2b:cd:7d:22:af:51:7e:9c:75:fe root@bogon
the key's randomart image is:
+--[ rsa 2048]----+
| |
| |
| . |
| . + |
| s b o . o|
| * * = o+|
| . o b +.=|
| . + +.|
| ... e|
+-----------------+
The ssh-cop-id command copies the specified public key file to the remote computer.
[root@bogon ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@10.1.250.166
the authenticity of host '10.1.250.166 (10.1.250.166)' can't be established.
rsa key fingerprint is c8:9d:6d:92:55:77:3d:3e:af:f5:cb:18:80:5a:47:93.
are you sure you want to continue connecting (yes/no)? yes
warning: permanently added '10.1.250.166' (rsa) to the list of known hosts.
reverse mapping checking getaddrinfo for bogon [10.1.250.166] failed - possible break-in attempt!
root@10.1.250.166's password:
now try logging into the machine, with "ssh 'root@10.1.250.166'", and check in:
.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.
3. Then ssh login host b to verify whether a password is required
[root@localhost ~]# ssh 10.1.250.166
reverse mapping checking getaddrinfo for bogon [10.1.250.166] failed - possible break-in attempt!
last login: wed oct 21 10:05:39 2015 from 10.1.250.141
[root@bogon ~]#
4. After successful login, we need to do the above 3 steps in host B, so that we can log in without password ssh. (If there are multiple hosts, do the same operation for each host to facilitate later management).
5. Question of authority
It is recommended to use other users to do ssh login, adjust the directory file permissions
Set authorized_keys permissions
chmod 644 authorized_keys
Set.ssh directory permissions
chmod 700 -r .ssh
Make sure that only the user has permission to write.ssh and authorized_keys. Otherwise validation is invalid.
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