Passwordless SSH

These instructions assume 2 ESXi servers: ESXi0 & ESXi1

Both of these servers have a datastore named Admin for Administrative stuff and a Folder named Utilities for storing useful things.

ESXi to ESXi

Source: How to SSH between ESXi 6.0U2 hosts without providing a password

The following 2 sections are basically lists of Copy-Pasta commands for each server.

ESXi0

• mkdir /vmfs/volumes/Admin/Utilities/ssl
• mkdir /vmfs/volumes/Admin/Utilities/ssl/ESXi1
• mkdir /vmfs/volumes/Admin/Utilities/ssl/ESXi1/keys
• mkdir /.ssh
• cd /.ssh
• /usr/lib/vmware/openssh/bin/ssh-keygen -t rsa -b 4096
• cat id_rsa.pub | ssh root@ESXi1 'cat >> /etc/ssh/keys-root/authorized_keys'
• cp /.ssh/* /vmfs/volumes/Admin/Utilities/ssl/ESXi1/keys
• vi /etc/rc.local.d/local.sh

mkdir /.ssh
cp /vmfs/volumes/Admin/Utilities/ssl/ESXi1/keys/* /.ssh

• /sbin/auto-backup.sh

ESXi1

• mkdir /vmfs/volumes/Admin/Utilities/ssl
• mkdir /vmfs/volumes/Admin/Utilities/ssl/ESXi0
• mkdir /vmfs/volumes/Admin/Utilities/ssl/ESXi0/keys
• mkdir /.ssh
• cd /.ssh
• /usr/lib/vmware/openssh/bin/ssh-keygen -t rsa -b 4096
• cat id_rsa.pub | ssh root@ESXi0 'cat >> /etc/ssh/keys-root/authorized_keys'
• cp /.ssh/* /vmfs/volumes/Admin/Utilities/ssl/ESXi0/keys
• vi /etc/rc.local.d/local.sh

mkdir /.ssh
cp /vmfs/volumes/Admin/Utilities/ssl/ESXi0/keys/* /.ssh

• /sbin/auto-backup.sh

On Both Servers

• chmod +t /etc/ssh/keys-root/authorized_keys
• vi /etc/ssh/sshd_config
• (Ensure the following items are in the file)

PermitRootLogin yes
UsePAM yes
# only use PAM challenge-response (keyboard-interactive)
PasswordAuthentication no 

• /etc/init.d/SSH restart

At this point, you should be able to SSH from one to the other without needing to enter a password.