sysctl 用来修改内核参数(/proc/sys/)

语法

sysctl [OPTIONS] [variable[=value]]
sysctl -p [FILE]

选项

-a, -A: 显示所有变量及值
-n: 只显示值
-w: 设置变量的值(临时)
-p: 从指定的文件读取变量和值修改内核参数(永久)，默认从/etc/sysctl.conf读取

示例：

查看所有内核参数

sysctl -a

输出：

net.core.rmem_default = 212992
net.core.rmem_max = 212992
net.core.rps_sock_flow_entries = 0
net.core.somaxconn = 128
net.core.warnings = 1
net.core.wmem_default = 212992
net.core.wmem_max = 212992
net.core.xfrm_acq_expires = 30
net.core.xfrm_aevent_etime = 10
net.core.xfrm_aevent_rseqth = 2
net.core.xfrm_larval_drop = 1
net.ipv4.cipso_cache_bucket_size = 10
net.ipv4.cipso_cache_enable = 1
net.ipv4.cipso_rbm_optfmt = 0
net.ipv4.cipso_rbm_strictvalid = 1
net.ipv4.conf.all.accept_local = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.arp_accept = 0
...

查看指定内核变量

sysctl net.ipv4.ip_forward

输出

net.ipv4.ip_forward = 1

临时修改指定内核变量的值

sysctl -w net.ipv4.ip_forward=0

永久修改，需要将变量写入/etc/sysct.conf 文件中

$ cat /etc/sysct.conf
net.ipv4.ip_forward = 1

然后加载文件，使配置生效

sysctl -p