Password-free login under Linux (super detailed)

This article mainly introduces the relevant information on password-free login under Linux. It is very good and has reference value. Friends who are interested should take a look together

1.Linux Generate keys under

ssh-keygen command manual, through the "man ssh-keygen" command:

Through the command" ssh-keygen -t rsa"

## After generation, a ".ssh" folder will be generated in the user's root directory

Entering ".ssh" will generate the following files

Authorized_keys: stores the public key for remote password-free login. This file is mainly used to record the information of multiple machines. Public key

id_rsa: generated private key file

id_rsa.pub: generated public key file

know_hosts: known Host public key list

If you want the ssh public key to be effective, at least the following two conditions must be met:

1) The permissions of the .ssh directory must be 700

2 ) .ssh/authorized_keys file permission must be 600

2. Remote password-free login

Schematic diagram:

The following methods are commonly used:

　

2.1 Through ssh-copy-id

Command:

ssh-copy-id -i ~/.ssh/id_rsa.put fe1be4b6c1a31021ce15f9d3346405e5

Example:

[root@test .ssh]# ssh-copy-id -i ~/.ssh/id_rsa.pub 192.168.91.135 
root@192.168.91.135's password: 
Now try logging into the machine, with "ssh '192.168.91.135'", and check in:

.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

[root@test .ssh]# ssh root@192.168.91.135
Last login: Mon Oct 10 01:25:49 2016 from 192.168.91.133
[root@localhost ~]#

Common errors:

[root@test ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub 192.168.91.135

　　　-bash: ssh-copy-id: command not found //Prompt command does not exist

　　　

Solution: yum -y install openssh-clients

　2.2 Write the content to the other party's file through scp

Command:

scp -p ~/.ssh/id_rsa.pub root@721b019b2c3c3f62b979c6ee04afb641:/root/.ssh/authorized_keys

Example:

[root@test .ssh]# scp -p ~/.ssh/id_rsa.pub root@192.168.91.135:/root/.ssh/authorized_keys
root@192.168.91.135's password: 
id_rsa.pub 100% 408 0.4KB/s 00:00 
[root@test .ssh]# 
[root@test .ssh]# 
[root@test .ssh]# 
[root@test .ssh]# ssh root@192.168.91.135
Last login: Mon Oct 10 01:27:02 2016 from 192.168.91.133
[root@localhost ~]#

can also be divided into two steps:

$ scp ~/.ssh/id_rsa.pub root@721b019b2c3c3f62b979c6ee04afb641:pub_key //Copy the file to the remote server

$ cat ~/pub_key >>~/.ssh/authorized_keys //Copy the content Append to the authorized_keys file, but you need to log in to the remote server to execute this command

　　

##2.3 Implement batch password exemption through Ansible

2.3.1 Add the machine hosts that require password-free operations to /etc/ansible/hosts:

　[Avoid close]

　192.168.91.132

　192.168.91.133
192.168.91.134

2.3.2 Execute the command for password-free operation

ansible 4179fd5bdbf839b03206a46852a78368 -m authorized_key -a "user=root key='{{ lookup ('file','/root/.ssh/id_rsa.pub') }}'" -k

Example:

[root@test sshpass-1.05]# ansible test -m authorized_key -a "user=root key='{{ lookup('file','/root/.ssh/id_rsa.pub') }}'" -k
　　SSH password: ----->输入密码
　　192.168.91.135 | success >> {
　　"changed": true, 
　　"key": "ssh-rsa 　　 AAAAB3NzaC1yc2EAAAABIwAAAQEArZI4kxlYuw7j1nt5ueIpTPWfGBJoZ8Mb02OJHR8yGW7A3izwT3/uhkK7RkaGavBbAlprp5bxp3i0TyNxa/apBQG5NiqhYO8YCuiGYGsQAGwZCBlNLF3gq1/18B6FV5moE/8yTbFA4dBQahdtVP PejLlSAbb5ZoGK8AtLlcRq49IENoXB99tnFVn3gMM0aX24ido1ZF9RfRWzfYF7bVsLsrIiMPmVNe5KaGL9kZ0svzoZ708yjWQQCEYWp0m+sODbtGPC34HMGAHjFlsC/SJffLuT/ug/hhCJUYeExHIkJF8OyvfC6DeF7ArI6zdKER7D8M0SM　　WQmpKUltj2nltuv3w== root@localhost.localdomain", 
　　"key_options": null, 
　　"keyfile": "/root/.ssh/authorized_keys", 
　　"manage_dir": true, 
　　"path": null, 
　　"state": "present", 
　　"unique": false, 
　　"user": "root"
　　}
　　[root@test sshpass-1.05]#

2.4 Manual copy and paste method Copy the contents of the local id_rsa.pub file to the ~/.ssh/authorized_keys file of the remote server

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