第十周作业—N42-虚怀若谷

一、编写脚本selinux.sh，实现开启或禁用SELinux功能

[root@centos7 ~]#vim selinux.sh 
#!/bin/bash

confdir=/etc/selinux/config

case "$1" in 

on)
  sed -ir 's/^SELINUX=.*/SELINUX=enforcing/' $confdir
  echo "Open The SELinux Success!"
  ;;
off)
  sed -ir 's/^SELINUX=.*/SELINUX=disable/' $confdir
  echo "Close The SELinux Success;But you should reboot to make selinux enabled!"
  ;;
*)
  echo "Usage:`basename $0` on|off"
  exit 1
  ;;
esac
[root@centos7 ~]# bash selinux.sh on
Open The SELinux Success!
[root@centos7 ~]# grep  "SELINUX=" /etc/selinux/config
# SELINUX= can take one of these three values:
SELINUX=enforcing
[root@centos7 ~]# bash selinux.sh off
Close The SELinux Success;But you should reboot to make selinux enabled!
[root@centos7 ~]# grep  "SELINUX=" /etc/selinux/config
# SELINUX= can take one of these three values:
SELINUX=disable

二、统计/etc/fstab文件中每个文件系统类型出现的次数 

#第一种方法
[root@centos7 ~]# awk '/^[^#]/{print $3}' /etc/fstab |sort |uniq -c
      1 swap
      3 xfs
#第二种方法 awk数组应用
[root@centos7 ~]# awk '/^[^#]/{num[$3]++}END{for(i in num) {print i,num[i]}}' /etc/fstab
swap 1
xfs 3

三、提取出字符串Yd$C@M05MB%9&Bdh7dq+YVixp3vpw中的所有数字

[root@centos7 ~]# echo 'Yd$C@M05MB%9&Bdh7dq+YVixp3vpw'|awk 'gsub(/[^0-9]/,"",$0)'
05973

四、解决DOS攻击生产案例:根据web日志或者或者网络连接数，监控当某个IP 并发连接数或者短时内PV达到100，即调用防火墙命令封掉对应的IP，监控频率每隔5分钟。防火墙命令为:iptables -A INPUT -s IP -j REJECT

#!/bin/bash

[ -n "$1" ] || { echo "Usage:`basename $0` file.log";exit 1; } #判断是否传有参数

file=$1

while true ; do
  awk '{print $1}' $1|grep -v "^$"|sort|uniq -c  > /tmp/tmp.log  #取出IP计数与IP
  exec < /tmp/tmp.log   #while读入文件
  while read line ; do
    ip=`echo $line|awk '{print $2}'`
    count=`echo $line|awk '{print $1}'`
    if [ $count -gt 100 ] && [ `iptables -vnL|grep "$ip"|wc -l` -lt 1 ];then
        iptables -A INPUT -s $IP -j REJECT
        echo "$ip is rejected" > /tmp/droplist_$(date +%F).log
    fi
  done
  sleep 300  #每分种监控一次
done