.编辑profile文件

[root@localhost ~]# vi /etc/profile


.在profile文件中添加如下内容

export PATH=$PATH:/usr/local/man

export PATH=$PATH:/usr/local/rabbitmq/sbin

export PATH="$PATH:/usr/local/webserver/mysql/bin"


.在profile文件中添加或修改的内容需要注销系统才能生效。同名的环境变量，后写入的起作用。或执行如下命令。

[root@localhost ~]# source /etc/profile

参考：https://www.cnblogs.com/lh03061238/p/9952659.html参考：https://www.jianshu.com/p/1dd22f5b521a
参考：https://blog.csdn.net/thebigdipperbdx/article/details/80862224

vm.swappiness =

net.ipv4.neigh.default.gc_stale_time=

net.ipv4.ip_forward =


# see details in https://help.aliyun.com/knowledge_detail/39428.html

net.ipv4.conf.all.rp_filter=

net.ipv4.conf.default.rp_filter=

net.ipv4.conf.default.arp_announce =

net.ipv4.conf.lo.arp_announce=

net.ipv4.conf.all.arp_announce=


# see details in https://help.aliyun.com/knowledge_detail/41334.html

net.ipv4.tcp_max_tw_buckets =

net.ipv4.tcp_syncookies =

net.ipv4.tcp_max_syn_backlog =

net.ipv4.tcp_synack_retries =


net.ipv6.conf.all.disable_ipv6 =

net.ipv6.conf.default.disable_ipv6 =

net.ipv6.conf.lo.disable_ipv6 =


kernel.sysrq=


# Linux禁止ping以及开启ping的方法，：允许，：禁止。执行sysctl -p使配置文件生效。网站攻击一般是从ping开始的。

net.ipv4.icmp_echo_ignore_all=

# 临时生效：echo  > /proc/sys/net/ipv4/icmp_echo_ignore_all

# 临时生效：sysctl -w net.ipv4.icmp_echo_ignore_all=1

# 参考：https://blog.csdn.net/yucdsn/article/details/81735328