SSH

• How to change the SSH Port in Linux
• Force SSH client to use Password Authentication
• ssh-keygen
• Change SSH Key Passphrase
• Remove SSH Private Key Passphrase
• SSH Remember Passphrase
• SSH Agent forwarding with tmux
• Auto Attach to tmux session on SSH
• List SSH keys
• PCI COMPLIANCE SSH Diffie-Hellman Modulus
• Allow SSH root login
• Email Alert When User Login Using SSH
• SSH Port Forwarding
• SSH Tunnel
• sshpass – non interactive password authentication from scripts.
• How to install dropbear SSH server
• How to create public key from SSH private key?
• How to SSH into SiteGround shared hosting account
• https://github.com/sshlog/agent/ – Log SSH session.

SSH Connection Errors

• no matching host key type found. Their offer: ssh-dss
• kex_exchange_identification: read: Connection reset by peer
• SSH Server refused our key
• userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms
• SSH Login Delay

SSH ProxyJump (Jump Host/bastion host)

• Force all SSH connection through Jump Host

SSH Errors

• SSH Too many authentication failures

SSH Protect

• Stop SSH bruteforce with endlessh

SSH Configuration Options

AllowUsers admin

Only allow a specific user to login.

DenyGroups customers

Deny SSH access to a Group. You can add multiple groups separated by space.

ClientAliveInterval 120

Disconnect if the client is inactive for 120 seconds.

Verify sshd configurations are correct

sshd -t

SSH connection delay on AlmaLinux

cat > /etc/ssh/sshd_config.d/10-tweaks.conf << 'EOF'
GSSAPIAuthentication no
GSSAPICleanupCredentials no
EOF

systemctl restart sshd