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# 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 maxmimum size of a mesage 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 = 209708 | |
# Do less swapping | |
vm.swappiness = 30 | |
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 256MB | |
kernel.shmmax = 268435456 | |
kernel.shmall = 268435456 | |
# Keep at least 64MB of free RAM space available | |
vm.min_free_kbytes = 65535 | |
### | |
### 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 = 300 | |
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 = 1 | |
# Allowed local port range | |
net.ipv4.ip_local_port_range = 16384 65535 | |
# Enable a fix for RFC1337 - time-wait assassination hazards in TCP | |
net.ipv4.tcp_rfc1337 = 1 | |
# Do not auto-configure IPv6 | |
net.ipv6.conf.all.autoconf=0 | |
net.ipv6.conf.all.accept_ra=0 | |
net.ipv6.conf.default.autoconf=0 | |
net.ipv6.conf.default.accept_ra=0 | |
net.ipv6.conf.eth0.autoconf=0 | |
net.ipv6.conf.eth0.accept_ra=0 | |
### | |
### TUNING NETWORK PERFORMANCE ### | |
### | |
# Use BBR TCP congestion control and set tcp_notsent_lowat to 16384 to ensure HTTP/2 prioritization works optimally | |
# Do a 'modprobe tcp_bbr' first (kernel > 4.9) | |
# Fall-back to htcp if bbr is unavailable (older kernels) | |
net.ipv4.tcp_congestion_control = htcp | |
net.ipv4.tcp_congestion_control = bbr | |
net.ipv4.tcp_notsent_lowat = 16384 | |
# For servers with tcp-heavy workloads, enable 'fq' queue management scheduler (kernel > 3.12) | |
net.core.default_qdisc = fq | |
# Turn on the tcp_window_scaling | |
net.ipv4.tcp_window_scaling = 1 | |
# Increase the read-buffer space allocatable | |
net.ipv4.tcp_rmem = 8192 87380 16777216 | |
net.ipv4.udp_rmem_min = 16384 | |
net.core.rmem_default = 262144 | |
net.core.rmem_max = 16777216 | |
# Increase the write-buffer-space allocatable | |
net.ipv4.tcp_wmem = 8192 65536 16777216 | |
net.ipv4.udp_wmem_min = 16384 | |
net.core.wmem_default = 262144 | |
net.core.wmem_max = 16777216 | |
# Increase number of incoming connections | |
net.core.somaxconn = 32768 | |
# Increase number of incoming connections backlog | |
net.core.netdev_max_backlog = 16384 | |
net.core.dev_weight = 64 | |
# Increase the maximum amount of option memory buffers | |
net.core.optmem_max = 65535 | |
# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks | |
net.ipv4.tcp_max_tw_buckets = 1440000 | |
# try to reuse time-wait connections, but don't recycle them (recycle can break clients behind NAT) | |
net.ipv4.tcp_tw_recycle = 0 | |
net.ipv4.tcp_tw_reuse = 1 | |
# Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory | |
net.ipv4.tcp_max_orphans = 16384 | |
net.ipv4.tcp_orphan_retries = 0 | |
# Limit the maximum memory used to reassemble IP fragments (CVE-2018-5391) | |
net.ipv4.ipfrag_low_thresh = 196608 | |
net.ipv6.ip6frag_low_thresh = 196608 | |
net.ipv4.ipfrag_high_thresh = 262144 | |
net.ipv6.ip6frag_high_thresh = 262144 | |
# don't cache ssthresh from previous connection | |
net.ipv4.tcp_no_metrics_save = 1 | |
net.ipv4.tcp_moderate_rcvbuf = 1 | |
# Increase size of RPC datagram queue length | |
net.unix.max_dgram_qlen = 50 | |
# Don't allow the arp table to become bigger than this | |
net.ipv4.neigh.default.gc_thresh3 = 2048 | |
# Tell the gc when to become aggressive with arp table cleaning. | |
# Adjust this based on size of the LAN. 1024 is suitable for most /24 networks | |
net.ipv4.neigh.default.gc_thresh2 = 1024 | |
# Adjust where the gc will leave arp table alone - set to 32. | |
net.ipv4.neigh.default.gc_thresh1 = 32 | |
# Adjust to arp table gc to clean-up more often | |
net.ipv4.neigh.default.gc_interval = 30 | |
# Increase TCP queue length | |
net.ipv4.neigh.default.proxy_qlen = 96 | |
net.ipv4.neigh.default.unres_qlen = 6 | |
# Enable Explicit Congestion Notification (RFC 3168), disable it if it doesn't work for you | |
net.ipv4.tcp_ecn = 1 | |
net.ipv4.tcp_reordering = 3 | |
# How many times to retry killing an alive TCP connection | |
net.ipv4.tcp_retries2 = 15 | |
net.ipv4.tcp_retries1 = 3 | |
# Avoid falling back to slow start after a connection goes idle | |
# keeps our cwnd large with the keep alive connections (kernel > 3.6) | |
net.ipv4.tcp_slow_start_after_idle = 0 | |
# Allow the TCP fastopen flag to be used, beware some firewalls do not like TFO! (kernel > 3.7) | |
net.ipv4.tcp_fastopen = 3 | |
# This will enusre that immediatly subsequent connections use the new values | |
net.ipv4.route.flush = 1 | |
net.ipv6.route.flush = 1 |
There is a comment "Tested with: Ubuntu 14.04 LTS kernel version 3.13" Does that mean it is not tested with Ubuntu 18.04?
@merc74
This can also be used with 18.04. 👍🏻
Thanks for the quick response.
It also says: #Intended use for dedicated server systems at high-speed networks with loads of RAM and bandwidth available.
I'm using your config on a dedicated server with only 2 gig of ram, but I have very high peeks of user's at specific times, and before it happens I do resize the server to 16 gig of ram because I have 1000 plus connection within 1 minute. I'm wondering if this config will be an issue when I'm only at 2gig of ram?
thank you for this
Here is more info about /etc/sysctl.conf file. https://www.howtouseubuntu.com/cloud/understanding-etc-sysctl-conf-file-in-linux/
There is a comment "Tested with: Ubuntu 14.04 LTS kernel version 3.13" Does that mean it is not tested with Ubuntu 18.04?