This is yet another post about the password-less login through ssh in linux.
Why do we need it? Because;
Especially in cluster systems, more than one host are running as one, nodes needs to communicate with each other frequently.
More than one host communicates each other for any reason. Foe example postgresql replications.
To enable ssh logins without password in a secure way is as follows;
Login to the user which will be able to login without password.
First we are going to create a public key.
Then, share the public key across nodes.
# on node 1
su - postgres
ssh-keygen -t rsa
cd .ssh
cat id_rsa.pub >> authorized_keys
# on node 2
su - postgres
ssh-keygen -t rsa
cd .ssh
cat id_rsa.pub >> authorized_keys# append the contents of the id_rsa.pub file on node 1 to the file ~/.ssh/authorized_keys file on node 2
# do the same the other way around, append the contents of id_rsa.pub file on node 2 to the file ~/.ssh/authorized_keys file on node 1
Now you should be able to open an ssh connection without password as follows
-bash-4.2$ hostname
pg12-01
-bash-4.2$ ssh pg12-02
Last login: Mon Jan 25 19:39:00 2021 from pg12-02
-bash-4.2$ hostname
pg12-02
-bash-4.2$ exit
logout
Connection to pg12-02 closed.
-bash-4.2$ hostnameOr even, run a command on the other node.
-bash-4.2$ ssh pg12-02 hostname;date
pg12-02
Mon Jan 25 19:43:21 +03 2021
-bash-4.2$ privileges on the .ssh folder and the contents are important, or else your setup may note work.
-bash-4.2$ ls -la
total 28
drwx------. 4 postgres postgres 91 Oct 23 04:40 .
drwxr-xr-x. 24 root root 4096 Oct 22 15:25 ..
drwx------. 6 postgres postgres 84 Oct 23 04:14 12
-rw-------. 1 postgres postgres 13669 Jan 25 19:39 .bash_history
-rwx------. 1 postgres postgres 296 Oct 22 16:07 .bash_profile
-rw-------. 1 postgres postgres 2547 Jan 25 19:00 .psql_history
drwx------. 2 postgres postgres 80 Jan 25 15:40 .ssh
-bash-4.2$
-bash-4.2$ ls -l .ssh
total 16
-rw-r--r--. 1 postgres postgres 796 Jan 25 15:39 authorized_keys
-rw-------. 1 postgres postgres 1675 Jan 25 15:31 id_rsa
-rw-r--r--. 1 postgres postgres 398 Jan 25 15:31 id_rsa.pub
-rw-r--r--. 1 postgres postgres 722 Jan 25 19:38 known_hosts
-bash-4.2$ ls -l
Comments