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Today, the editor will share with you the relevant knowledge points about how to use the sysctl command of Linux. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look.

The Linux common command sysctl command is used to dynamically modify kernel running parameters while the kernel is running, and the available kernel parameters are in the directory / proc/sys.

Dynamically modify kernel running parameters during sysctl

Add that it includes some advanced options for TCP/ip stacks and virtual memory systems, which allow experienced administrators to improve eye-catching system performance. You can read and set more than five hundred system variables with sysctl.

Syntax sysctl (options) (parameters) option-n: do not print keywords when printing values;-e: ignore unknown keyword errors;-N: print only names;-w: use this when changing sysctl settings;-p: load kernel parameter settings from configuration file "/ etc/sysctl.conf";-a: print all currently available kernel parameter variables and values -A: prints all currently available kernel parameter variables and values in tabular form. Parameter variable = value: sets the value of the variable corresponding to the kernel parameter.

Instance to view all readable variables:

Sysctl-a

Read a specified variable, such as kern.maxproc:

Sysctl kern.maxproc kern.maxproc: 1044

To set a specified variable, use syntax such as variable=value directly:

Sysctl kern.maxfiles=5000 kern.maxfiles: 2088-> 5000 you can use sysctl to modify system variables, or you can modify system variables by editing the sysctl.conf file. Sysctl.conf looks a lot like rc.conf. It sets the value in the form of variable=value. The specified value is set after the system enters multi-user mode. Not all variables can be set in this mode.

The sysctl variable is usually set as a string, number, or Boolean. (Boolean means 1 for 'yes',' and 0 for 'no').

Sysctl-w kernel.sysrq=0 sysctl-w kernel.core_uses_pid=1 sysctl-w net.ipv4.conf.default.accept_redirects=0 sysctl-w net.ipv4.conf.default.accept_source_route=0 sysctl-w net.ipv4.conf.default.rp_filter=1 sysctl-w net.ipv4.tcp_syncookies=1 sysctl-w net.ipv4.tcp_max_syn_backlog=2048 sysctl-w net.ipv4.tcp_fin_timeout=30 sysctl-w net.ipv4.tcp_synack_retries=2 sysctl-w net.ipv4.tcp_keepalive_time=3600 Sysctl-w net.ipv4.tcp_window_scaling=1 sysctl-w net.ipv4.tcp_sack=1 configuration sysctl edit this file: / etc/sysctl.conf

If the file is empty, enter the following, otherwise adjust yourself according to the situation:

# Controls source route verification # Default should work for all interfaces net.ipv4.conf.default.rp_filter = 1 # net.ipv4.conf.all.rp_filter = 1 # net.ipv4.conf.lo.rp_filter = 1 # net.ipv4.conf.eth0.rp_filter = 1 # Disables IP source routing # Default should work for all interfaces net.ipv4.conf.default.accept_source_route = 0 # net.ipv4.conf.all.accept_source_route = 0 # net.ipv4.conf.lo. Accept_source_route = 0 # net.ipv4.conf.eth0.accept_source_route = 0 # 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 # Increase maximum amount of memory allocated to shm # Only uncomment if needed! # kernel.shmmax = 67108864 # Disable ICMP Redirect Acceptance # Default should work for all interfaces net.ipv4.conf.default.accept_redirects = 0 # net.ipv4.conf.all.accept_redirects = 0 # net.ipv4.conf.lo.accept_redirects = 0 # net.ipv4.conf.eth0.accept_redirects = 0 # enable Log Spoofed Packets, Source Routed Packets Redirect Packets # Default should work for all interfaces net.ipv4.conf.default.log_martians = 1 # net.ipv4.conf.all.log_martians = 1 # net.ipv4.conf.lo.log_martians = 1 # net.ipv4.conf.eth0.log_martians = 1 # Decrease the time default value for tcp_fin_timeout connection net.ipv4.tcp_fin_timeout = 25 # Decrease the time default value for tcp_keepalive_time connection net.ipv4.tcp_keepalive_time = 1200 # Turn on the tcp _ window_scaling net.ipv4.tcp_window_scaling = 1 # Turn on the tcp_sack net.ipv4.tcp_sack = 1 # tcp_fack should be on because of sack net.ipv4.tcp_fack = 1 # Turn on the tcp_timestamps net.ipv4.tcp_timestamps = 1 # Enable TCP SYN Cookie Protection net.ipv4.tcp_syncookies = 1 # Enable ignoring broadcasts request net.ipv4.icmp_echo_ignore_broadcasts = 1 # Enable bad error message Protection net.ipv4.icmp_ignore_bogus _ error_responses = 1 # make more local ports available # net.ipv4.ip_local_port_range = 1024 65000 # set TCP Re-Ordering value in kernel to'5' net.ipv4.tcp_reordering = 5 # Lower syn retry rates net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_syn_retries = 3 # Set Max SYN Backlog to '2048' net.ipv4.tcp_max_syn_backlog = 2048 # Various Settings net.core.netdev_max_backlog = 1024 # Increase The maximum number of skb-heads to be cached net.core.hot_list_length = 360000 # Increase the tcp-time-wait buckets pool size net.ipv4.tcp_max_tw_buckets = 360000 # This will increase the amount of memory available for socket input/output queues net.core.rmem_default = 65535 net.core.rmem_max = 8388608 net.ipv4.tcp_rmem = 4096 87380 8388608 net.core.wmem_default = 65535 net.core.wmem_max = 8388608 net.ipv4.tcp_wmem = 4096 65535 8388608 Net.ipv4.tcp_mem = 8388608 8388608 8388608 net.core.optmem_max = 40960 if you want to block others from ping your host Then add the following code:

# Disable ping requests net.ipv4.icmp_echo_ignore_all = 1 after editing, execute the following command to make the changes take effect immediately:

/ sbin/sysctl-p / sbin/sysctl-w net.ipv4.route.flush=1 above is all the content of this article "how to use the sysctl command of Linux". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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