sysctl.conf

sysctl.conf

# Kernel sysctl configuration file for Linux
#
# Version 1.14 - 2019-04-05
# Michiel Klaver - IT Professional
# http://klaver.it/linux/ for the latest version - http://klaver.it/bsd/ for a BSD variant
#
# This file should be saved as /etc/sysctl.conf and can be activated using the command:
# sysctl -e -p /etc/sysctl.conf
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and sysctl.conf(5) for more details.
#
# Tested with: Ubuntu 14.04 LTS kernel version 3.13
#              Debian 7 kernel version 3.2
#              CentOS 7 kernel version 3.10

#
# Intended use for dedicated server systems at high-speed networks with loads of RAM and bandwidth available
# Optimised and tuned for high-performance web/ftp/mail/dns servers with high connection-rates
# DO NOT USE at busy networks or xDSL/Cable connections where packetloss can be expected
# ----------

# Credits:
# http://www.enigma.id.au/linux_tuning.txt
# http://www.securityfocus.com/infocus/1729
# http://fasterdata.es.net/TCP-tuning/linux.html
# http://fedorahosted.org/ktune/browser/sysctl.ktune
# http://www.cymru.com/Documents/ip-stack-tuning.html
# http://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
# http://www.frozentux.net/ipsysctl-tutorial/chunkyhtml/index.html
# http://knol.google.com/k/linux-performance-tuning-and-measurement
# http://www.cyberciti.biz/faq/linux-kernel-tuning-virtual-memory-subsystem/
# http://www.redbooks.ibm.com/abstracts/REDP4285.html
# http://www.speedguide.net/read_articles.php?id=121
# http://lartc.org/howto/lartc.kernel.obscure.html
# http://en.wikipedia.org/wiki/Sysctl
# https://blog.cloudflare.com/http-2-prioritization-with-nginx/



###
### GENERAL SYSTEM SECURITY OPTIONS ###
###

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid = 1

# Allow for more PIDs
kernel.pid_max = 65535

# The contents of /proc/<pid>/maps and smaps files are only visible to
# readers that are allowed to ptrace() the process
kernel.maps_protect = 1

# Enable ExecShield protection
kernel.exec-shield = 1
kernel.randomize_va_space = 2

# Controls the maximum size of a message, in bytes
kernel.msgmnb = 65535

# Controls the default maximum size of a message queue
kernel.msgmax = 65535

# Restrict core dumps
fs.suid_dumpable = 0

# Hide exposed kernel pointers
kernel.kptr_restrict = 1



###
### IMPROVE SYSTEM MEMORY MANAGEMENT ###
###

# Increase size of file handles and inode cache
fs.file-max = 1000000

# Do less swapping
vm.swappiness = 10
vm.dirty_ratio = 30
vm.dirty_background_ratio = 5

# Specifies the minimum virtual address that a process is allowed to mmap
vm.mmap_min_addr = 4096

# 50% overcommitment of available memory
vm.overcommit_ratio = 50
vm.overcommit_memory = 0

# Set maximum amount of memory allocated to shm to 8GB (adjust based on your system's RAM)
kernel.shmmax = 8589934592
kernel.shmall = 2097152

# Keep at least 256MB of free RAM space available
vm.min_free_kbytes = 262144



###
### GENERAL NETWORK SECURITY OPTIONS ###
###

# Prevent SYN attack, enable SYNcookies (they will kick-in when the max_syn_backlog reached)
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_max_syn_backlog = 4096

# Disables packet forwarding
net.ipv4.ip_forward = 0
net.ipv4.conf.all.forwarding = 0
net.ipv4.conf.default.forwarding = 0
net.ipv6.conf.all.forwarding = 0
net.ipv6.conf.default.forwarding = 0

# Disables IP source routing
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0

# Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout = 7

# Decrease the time default value for connections to keep alive
net.ipv4.tcp_keepalive_time = 120
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15

# Don't relay bootp
net.ipv4.conf.all.bootp_relay = 0

# Don't proxy arp for anyone
net.ipv4.conf.all.proxy_arp = 0

# Turn on the tcp_timestamps, accurate timestamp make TCP congestion control algorithms work better
net.ipv4.tcp_timestamps = 1

# Don't ignore directed pings
net.ipv4.icmp_echo_ignore_all = 0

# Enable ignoring broadcasts request
net.ipv4.icmp_echo_ignore_broadcasts = 1

# Enable bad error message Protection
net.ipv4.icmp_ignore_bogus_error_responses = ::contentReference[oaicite:0]{index=0}