9 Essential Linux Server Optimization Tips for Faster, Safer Operations

1. Time Synchronization

Accurate time is critical; for a mail server using Dovecot, time drift caused service stops. Edit /etc/crontab and add a daily NTP sync:

14 04 * * * root /usr/sbin/ntpdate ntp.api.bz > /dev/null 2>&1

2. Enable SYN Cookie Protection

Activate kernel SYN cookies: echo "1" > /proc/sys/net/ipv4/tcp_syncookies Apply immediately:

/sbin/sysctl -p

3. Fix Slow Squid Server

When Squid slows down, run:

netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'

Adjust kernel parameters in /etc/sysctl.conf:

net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_max_syn_backlog = 8192
net.ipv4.tcp_max_tw_buckets = 5000

Apply:

/sbin/sysctl -p

4. Nginx Server Settings

For Nginx load balancers or Nginx+PHP5 web servers, enable:

net.ipv4.tcp_tw_reuse = 1   # reuse TIME-WAIT sockets
net.ipv4.tcp_tw_recycle = 1 # fast recycle TIME-WAIT sockets

Apply:

/sbin/sysctl -p

5. Increase Max Open Files

Modify /etc/security/limits.conf and add:

* soft nofile 60000
* hard nofile 65535

Note: ulimit -SHn or editing /etc/rc.d/rc.local cannot change the system limit.

6. Run Only Required Services

Enable essential services only, e.g.:

crond irqbalance microcode_ctl network random sshd syslog

Check services at runlevel 5:

chkconfig --list | awk '{print $1 " " $7}' | grep 5:on

Stop and disable unnecessary services such as cups:

service cups stop
chkconfig cups off

7. Disable IPv6

Edit /etc/modprobe.conf and append:

alias net-pf-10 off
alias ipv6 off
echo "IPV6INIT=no" >> /etc/sysconfig/network-scripts/ifcfg-eth0

8. Enable RHEL NIC ONBOOT

For RHEL, edit /etc/sysconfig/network-scripts/ifcfg-eth0 (or eth1) and set: ONBOOT=YES Then restart network:

service network restart

9. Linux Memory Management

Linux uses available memory aggressively; it employs buffer cache and page cache to speed up disk I/O. The default behavior is generally optimal, so manual tuning is rarely needed.