Batch Configure SSH Passwordless Login

Ruohang FengPigsty founder, PostgreSQL mage, database guru, cloud-exit evangelist

Configuring SSH is fundamental operations work - sometimes the basics need revisiting.

Generate Public-Private Key Pairs

Ideally, everything should use public-private key authentication for passwordless direct connection from local to all database machines. Password authentication should be avoided.

First, use ssh-keygen to generate public-private key pairs:

ssh-keygen -t rsa

Pay attention to permissions: SSH files should have permissions set to 0600, and .ssh directory permissions should be set to 0700. Incorrect settings will prevent passwordless login from working.

Configure ssh config to traverse jumphost

Replace User with your own name. Put in .ssh/config. Here’s how to configure direct passwordless connection to production database in a jumphost environment:

# Vonng's ssh config

# SpringBoard IP
Host <BastionIP>
	Hostname <your_ip_address>
	IdentityFile ~/.ssh/id_rsa

# Target Machine Wildcard (Proxy via Bastion)
Host 10.xxx.xxx.*
	ProxyCommand ssh <BastionIP> exec nc %h %p 2>/dev/null
	IdentityFile ~/.ssh/id_rsa

# Common Settings
Host *
	User xxxxxxxxxxxxxx
	PreferredAuthentications publickey,password
	Compression yes
	ServerAliveInterval 30
	ControlMaster auto
	ControlPath ~/.ssh/ssh-%r@%h:%p
	ControlPersist yes
	StrictHostKeyChecking no

Copy Public Key to Target Machines

Then copy the public key to jumphost, DBA workstation, and all database machines.

ssh-copy-id <target_ip>

Each execution of this command requires password input, which is tedious and boring. It can be automated through expect scripts or using sshpass.

Use expect for Automation

Replace <your password> in the following script with your actual password. If the server IP list changes, modify the list accordingly.

#!/usr/bin/expect
foreach id { 
     10.xxx.xxx.xxx
     10.xxx.xxx.xxx
     10.xxx.xxx.xxx
} {
    spawn ssh-copy-id $id
    expect {
    	"*(yes/no)?*"
    	{
            send "yes\n"
            expect "*assword:" { send "<your password>\n"}
    	}
     	"*assword*" { send "<your password>\n"}
    }
}

exit

More Elegant Solution: sshpass

sshpass -p <your password> ssh-copy-id <target address>

The downside is that passwords are likely to appear in bash history - clean up traces promptly after execution.