SSH Remote Password free login

Password free login operation

One 、ssh-keygen Generate key pair

[email protected] ~ % ssh-keygen         [0]
Generating public/private rsa key pair.
Enter file in which to save the key (/home/lj/.ssh/id_rsa): 
Created directory '/home/lj/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/lj/.ssh/id_rsa
Your public key has been saved in /home/lj/.ssh/id_rsa.pub
The key fingerprint is:
SHA256:xyIbEYaUdvQDIOIXMknL57YgT2jYFv292D+aZP2612c [email protected]
The key's randomart image is:
+---[RSA 3072]----+
|o+ooo==          |
|oo+o=..+         |
| +.+... o        |
|.o+. . o o       |
|+o+o  + S o      |
|o+o .  * =       |
|  ..  o = .  .   |
|       o o... . E|
|        o.+=.  o |
+----[SHA256]-----+

Can be viewed after generation

[email protected] ~ % cd .ssh/        [0]
[email protected] .ssh % ls        [0]
id_rsa  id_rsa.pub
[email protected] .ssh % cat id_rsa.pub          [0]
ssh-rsa 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 [email protected]

Two 、 The public key is copied to another machine

I use the virtual machine here Ubuntu The remote access CentOS
First you need to look at ip
CentOS Of IP yes 192.168.145.128

[[email protected] ~]$ ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:13:79:ad brd ff:ff:ff:ff:ff:ff
    inet 192.168.145.128/24 brd 192.168.145.255 scope global dynamic eth0
       valid_lft 1775sec preferred_lft 1775sec
    inet6 fe80::20c:29ff:fe13:79ad/64 scope link 
       valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 52:54:00:cb:1c:48 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr0 state DOWN group default qlen 1000
    link/ether 52:54:00:cb:1c:48 brd ff:ff:ff:ff:ff:ff
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether 02:42:e3:4d:ba:d1 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever

Ubuntu Medium IP yes 192.168.145.129

[email protected] ~ % ip addr          [127]
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:e7:d2:56 brd ff:ff:ff:ff:ff:ff
    altname enp2s1
    inet 192.168.145.129/24 brd 192.168.145.255 scope global dynamic noprefixroute ens33
       valid_lft 1339sec preferred_lft 1339sec
    inet6 fe80::2b52:7877:23ac:71e8/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

Ubuntu The remote access CentOS： ssh-copy-id [email protected]

ssh-copy-id user name @ The other machine's IP Address

[email protected] .ssh % ssh-copy-id [email protected]        [0]
The authenticity of host '192.168.145.128 (192.168.145.128)' can't be established. ECDSA key fingerprint is SHA256:x9niIRejGoMuTiInyW0Ube4CFq7HrRggKzcsFcIz7nY. Are you sure you want to continue connecting (yes/no/[fingerprint])? yes /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys [email protected]'s password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh '[email protected]'"
and check to make sure that only the key(s) you wanted were added.

After logging in, you can ubuntu On the operation CentOS

[email protected] ~ % ssh [email protected]            [0]
Last login: Thu Jun 23 23:30:31 2022
[[email protected] ~]$ ls
Desktop  Documents  fabric  git-2.28.0    Library  Music     Public     Videos

The first picture below is Ubuntu System , The second picture is CentOS System
After successful remote login, enter ls What you see is CentOS What's in the system