How to Change Kernel Parameters

Prerequisites

Before changing kernel parameters, make sure you have:

SSH access to your VPS
Root or sudo privileges

⚠️ Incorrect kernel parameters can cause system instability. Only change parameters you understand.

Step 1: View Current Kernel Parameters

Connect to your VPS:

ssh hxroot@YOUR_SERVER_IP -p 22

sysctl -a

To filter specific parameters:

sysctl -a | grep net.ipv4.tcp

Step 2: Temporary Changes (Apply Until Reboot)

sudo sysctl -w net.ipv4.tcp_tw_reuse=1

Step 3: Permanent Changes (Edit /etc/sysctl.conf)

sudo nano /etc/sysctl.conf

Add lines at the end:

# TCP performance tuning
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.ip_local_port_range = 1024 65535
net.core.somaxconn = 1024
net.core.netdev_max_backlog = 5000
net.ipv4.tcp_max_syn_backlog = 4096
net.ipv4.tcp_syncookies = 1

Step 4: Apply Changes

sudo sysctl -p

This reloads all settings from /etc/sysctl.conf.

Common Tuning Parameters

Parameter	Description	Typical Value
net.ipv4.tcp_tw_reuse	Reuse TIME_WAIT sockets	1
net.ipv4.tcp_fin_timeout	Time to keep sockets in FIN-WAIT-2	30
net.ipv4.tcp_keepalive_time	Keepalive idle time (seconds)	1200
net.ipv4.ip_local_port_range	Local port range	1024 65535
net.core.somaxconn	Max backlog for listen()	1024
net.core.rmem_max	Max receive buffer size	134217728
net.core.wmem_max	Max send buffer size	134217728

Apply Specific Parameters with sysctl.conf Snippets

Create separate file for network tuning:

sudo nano /etc/sysctl.d/99-network.conf

Add parameters, then apply:

sudo sysctl -p /etc/sysctl.d/99-network.conf

Revert to Defaults

Remove or comment out custom lines in /etc/sysctl.conf, then:

sudo sysctl -p

✅ Kernel parameters have been updated. Monitor system performance to ensure desired results.