#sysctl config

New Post has been published on http://websetnet.com/sysctl-conf/

sysctl.conf

Ubuntu server out of box is not optimized to make full use of available hardware. This means “out-of-box” setup might fail under high load.

So we need to tweak system configuration for maximum concurrancy.

Sysctl Tweaks

Open

vim /etc/sysctl.conf

Add following towards bottom

### IMPROVE SYSTEM MEMORY MANAGEMENT ### # Increase size of file handles and inode cache fs.file-max = 2097152 # Do less swapping vm.swappiness = 10 vm.dirty_ratio = 60 vm.dirty_background_ratio = 2 ### GENERAL NETWORK SECURITY OPTIONS ### # Number of times SYNACKs for passive TCP connection. net.ipv4.tcp_synack_retries = 2 # Allowed local port range net.ipv4.ip_local_port_range = 2000 65535 # Protect Against TCP Time-Wait net.ipv4.tcp_rfc1337 = 1 # Decrease the time default value for tcp_fin_timeout connection net.ipv4.tcp_fin_timeout = 15 # 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 ### TUNING NETWORK PERFORMANCE ### # Default Socket Receive Buffer net.core.rmem_default = 31457280 # Maximum Socket Receive Buffer net.core.rmem_max = 12582912 # Default Socket Send Buffer net.core.wmem_default = 31457280 # Maximum Socket Send Buffer net.core.wmem_max = 12582912 # Increase number of incoming connections net.core.somaxconn = 65536 # Increase number of incoming connections backlog net.core.netdev_max_backlog = 65536 # Increase the maximum amount of option memory buffers net.core.optmem_max = 25165824 # Increase the maximum total buffer-space allocatable # This is measured in units of pages (4096 bytes) net.ipv4.tcp_mem = 65536 131072 262144 net.ipv4.udp_mem = 65536 131072 262144 # Increase the read-buffer space allocatable net.ipv4.tcp_rmem = 8192 87380 16777216 net.ipv4.udp_rmem_min = 16384 # Increase the write-buffer-space allocatable net.ipv4.tcp_wmem = 8192 65536 16777216 net.ipv4.udp_wmem_min = 16384 # Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks net.ipv4.tcp_max_tw_buckets = 1440000 net.ipv4.tcp_tw_recycle = 1 net.ipv4.tcp_tw_reuse = 1

Load Changes

Run following command to load changes to sysctl.

sysctl -p

Useful Systcl Commands

Show all system parameters with their values (default or changed)

sysctl -A

Show values of parameters modified by you

sysctl -p

Show value for a single parameter  parameter-name

sysctl parameter-name

Change value for  a single parameter parameter-name without editing sysctl.conf manually.

sysctl -w parameter-name=parameter-value

Above command will overwrite any previous modifications to parameter-name. Also, you may need to surround parameter-value with quotes.

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