1、编写脚本selinux.sh，实现开启或禁用SELinux功能
~]# cat selinux.sh
#!/bin/bash
script=$(basename $0)
function usage(){
echo -e "\nUSAGE: $SCRIPT [on | off] \n"
exit 1
}
if [ $# -ne 1 ];then
usage
fi
if [ $1 == 'off' ];then
setenforce 0
sed -i 's/^SELINUX=enforcing$/SELINUX=disabled/' /etc/selinux/config
fi
if [ $1 == 'on' ];then
setenforce 1
sed -i 's/^SELINUX=disabled$/SELINUX=enforcing/' /etc/selinux/config
fi
echo -n "SELinux status: "
getenforce
~]# sh selinux.sh
USAGE: [on | off]
~]# sh selinux.sh off
SELinux status: Permissive
~]# sh selinux.sh on
SELinux status: Enforcing
2、统计/etc/fstab文件中每个文件系统类型出现的次数
~]# cat fstab_stat.sh
#!/bin/bash
declare -A fs_dict
while read LINE
do
if [[ $LINE =~ ^#.* ]];then
continue
fi
if [ -n "$LINE" ];then
fs_type=$(echo $LINE | cut -d ' ' -f3)
let fs_dict[$fs_type]++
fi
done < /etc/fstab
for fs in ${!fs_dict[@]}
do
echo "$fs=${fs_dict[$fs]}"
done
~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Thu Jul 18 04:17:15 2019
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos-root / xfs defaults 0 0
UUID=0cb71780-8808-412d-b756-1a1b9931af93 /boot xfs defaults 0 0
/dev/mapper/centos-swap swap swap defaults 0 0
~]# sh fstab_stat.sh
swap=1
xfs=2
3、提取出字符串Yd$C@M05MB%9&Bdh7dq+YVixp3vpw中的所有数字
~]# cat str_seq.sh
#!/bin/bash
str="Yd$C@M05MB%9&Bdh7dq+YVixp3vpw"
for i in `seq ${#str}`
do
let idx=$i-1;
charx=${str:$idx:1}
if echo $charx | grep '[0-9]' &> /dev/null;then
echo $charx
fi
done
~]# sh str_seq.sh
0
5
9
7
3
4、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
~]# cat dos_filter.sh
#!/bin/bash
iplist=`ss -tan state established '( sport = :80 )' | awk '{print $4}'| cut -d':' -f1 | sort | uniq -c | awk '{if($1>10)print $2}'`
for ip in $iplist
do
iptables -A INPUT -s $ip -j REJECT
echo "$ip is REJECT!"
done
# 定时每5分钟执行一次，对本地的http服务进行监控
~]# crontab -e
*/5 * * * * /bin/bash /root/dos_filter.sh
# 在另外一台机器上，使用 apache 自带的压力测试工具 ab 模拟 http 并发请求
~]# ab -c 50 -n 100000 http://192.168.58.129/index.html
