Boost Linux Server Performance: Essential Kernel and File Limit Tweaks

1. Increase file descriptor limits

For the current shell:

ulimit -n 102400

echo "ulimit -n 102400" >> ~/.bashrc

For all users, edit /etc/security/limits.conf:

* soft nofile 102400

* hard nofile 102400

For the system-wide limit:

cat /proc/sys/fs/file-max

echo 1024000 > /proc/sys/fs/file-max

2. Adjust TCP kernel parameters

Edit /etc/sysctl.conf and add:

net.ipv4.ip_local_port_range = 1024 65000

net.ipv4.ip_conntrack_max = 10240

Apply the changes: sudo sysctl -p 3. Enable TCP TIME_WAIT reuse and recycle

In /etc/sysctl.conf add:

net.ipv4.tcp_tw_reuse = 1

net.ipv4.tcp_tw_recycle = 1

Apply immediately: sudo sysctl -p Understanding net.ipv4.tcp_max_syn_backlog

This kernel parameter controls the size of the SYN‑RECEIVED queue, which defaults to 512 or 1024. When the queue is full, the system stops accepting new TCP connections, helping prevent resource exhaustion. Increase it if you need to handle more simultaneous connection attempts.

Example to view the current value: cat /proc/sys/net/ipv4/tcp_max_syn_backlog On CentOS the default is 1024. To raise it, edit /etc/sysctl.conf and set, for example: net.ipv4.tcp_max_syn_backlog = 2048 Then reload:

sudo sysctl -p