How to Keep SSH Session Alive

Prerequisites

Before configuring SSH keep-alive, make sure you have:

• SSH access to your VPS
• Root or sudo privileges (for server-side config)

Method 1: Client-Side Configuration (Local Machine)

Edit your local SSH config file:

nano ~/.ssh/config

Add these lines:

Host *
    ServerAliveInterval 60
    ServerAliveCountMax 10

Or for specific host only:

Host YOUR_SERVER_IP
    ServerAliveInterval 60
    ServerAliveCountMax 10

What these do:

• ServerAliveInterval 60 - Send keep-alive packet every 60 seconds
• ServerAliveCountMax 10 - Allow 10 failures before disconnecting

Method 2: Command Line Option

Connect with keep-alive enabled:

ssh -o ServerAliveInterval=60 hxroot@YOUR_SERVER_IP -p 22

Method 3: Server-Side Configuration (All Users)

Edit SSH server config:

sudo nano /etc/ssh/sshd_config

Add or modify:

ClientAliveInterval 60
ClientAliveCountMax 10

Restart SSH service:

sudo systemctl restart sshd

Method 4: Using tmux or screen (Session Persistence)

These tools keep your session running even after disconnect:

tmux new -s mysession

Run your work, then detach:

Ctrl+B, then D

Later reattach:

tmux attach -t mysession

With screen:

screen -S mysession

Ctrl+A, then D

screen -r mysession

Method 5: Using autossh (Reconnects Automatically)

Install autossh:

apt install autossh -y

Use autossh:

autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" hxroot@YOUR_SERVER_IP

Method 6: Configure PuTTY (Windows)

1. Open PuTTY
2. Go to Connection
3. Set Seconds between keepalives to 60
4. Save the session

Method 7: Add to Bash Profile (Auto Apply)

Add to ~/.bashrc on your local machine:

alias ssh-keep='ssh -o ServerAliveInterval=60 -o ServerAliveCountMax=10'

Then use:

source ~/.bashrc

ssh-keep hxroot@YOUR_SERVER_IP

Check Current TCP Keep-Alive Settings

On your server:

sudo sysctl net.ipv4.tcp_keepalive_time

sudo sysctl net.ipv4.tcp_keepalive_intvl

sudo sysctl net.ipv4.tcp_keepalive_probes

Why SSH Sessions Disconnect

• Network firewalls dropping idle connections
• ISP timeout policies
• NAT table cleanup
• Router session timeouts
• Corporate proxy timeouts

Test Your Keep-Alive Settings

Leave SSH session idle for 5-10 minutes. If still connected, it works.

Monitor connection:

watch -n 1 "echo 'Session is alive at $(date)'"