When working with SSH sessions on Ubuntu Server, you might encounter a peculiar situation where your keyboard input isn't displayed in the terminal, yet commands still execute. This typically manifests when:

• Switching between terminal windows
• After periods of inactivity
• When using terminal multiplexers like screen or tmux

The root cause usually relates to TTY (teletype) configuration and terminal echo settings. The terminal stops displaying your input because:

stty -a | grep echo
# Should show "echo" in the output. If not, echo is disabled

Reset terminal settings:

reset
# Or alternatively:
stty sane

Force echo re-enablement:

stty echo
# If that doesn't work, try:
echo -e "\\033c"

SSH client configuration: Add these to your ~/.ssh/config

Host *
    ServerAliveInterval 60
    TCPKeepAlive yes
    EscapeChar none

Server-side TTY fixes:

# Add to /etc/ssh/sshd_config
ClientAliveInterval 60
ClientAliveCountMax 3

For multiplexer-specific issues, try these solutions:

# For screen:
screen -X eval "msgminwait 0" "msgwait 1"

# For tmux:
tmux set-window-option -g automatic-rename off

To inspect current terminal settings:

# Show all terminal settings
stty -a

# Check if input is being processed
cat -v
# Type some characters, should see raw input

Mismatched TERM variables can cause display issues:

# Check current terminal type
echo $TERM

# Set appropriate terminal (usually xterm-256color)
export TERM=xterm-256color

Add these to your shell startup files (~/.bashrc or ~/.zshrc):

# Prevent TTY issues
if [ -n "$SSH_CONNECTION" ]; then
    trap 'stty echo' EXIT
    stty sane
fi

---

When working with Ubuntu Server via SSH (from either Putty on Windows or native Linux clients), you might encounter a situation where:

• Input characters stop displaying in terminal after minimizing/restoring window
• Commands still execute normally (e.g., typing "ls" produces directory listing)
• Issue persists across terminal emulators but requires bash restart

This typically occurs due to TTY echo configuration getting corrupted. Several triggers can cause this:

# Check current tty settings (should show "echo" in output)
stty -a | grep echo

# Common causes:
1. Background processes modifying terminal settings
2. Terminal emulator sending incorrect escape sequences
3. Shell configuration files (.bashrc, .profile) with problematic stty commands

Try these before restarting your session:

# Method 1: Reset terminal (most effective)
reset

# Method 2: Manually enable echo
stty echo

# Method 3: Alternative reset method
echo -e "\033c"

SSH Server Configuration

Add these to /etc/ssh/sshd_config:

# Prevent SSH from modifying terminal parameters
PermitUserEnvironment no
UseLogin no

Client-Side Protection

For Putty users:

1. Go to Connection → SSH → TTY → TTY modes
2. Set "echo" to "Auto"

For Linux/Mac clients:

# Add to ~/.ssh/config
Host *
    SendEnv LANG LC_*
    ServerAliveInterval 60
    EscapeChar none

When using terminal multiplexers:

# For screen users
screen -X eval "echo on"

# For tmux users
tmux set-window-option force-width 80
tmux refresh-client

Create a troubleshooting script named tty_check.sh:

#!/bin/bash
echo "=== TTY Status Check ==="
echo "TTY: $(tty)"
echo "Echo status: $(stty -a | grep echo)"
echo "Terminal type: $TERM"
echo "SSH Client: $SSH_CLIENT"
echo "=== Current Settings ==="
stty -a