进程管理和计划任务

1、显示统计占用系统内存最多的进程，并排序。

[root@localhost ~]# ps axo pid,cmd,%cpu,%mem --sort -%mem
  PID CMD                         %CPU %MEM
 5516 /opt/py3/bin/python3.6 /opt  0.0  1.8
 5514 /opt/py3/bin/python3.6 /opt  0.0  1.7
 5510 /opt/py3/bin/python3.6 /opt  0.0  1.7
 5546 /opt/py3/bin/python3.6 /opt  0.1  1.7
 5512 /opt/py3/bin/python3.6 /opt  0.0  1.6
 5561 /opt/py3/bin/python3.6 /opt  0.0  1.6
 5518 /opt/py3/bin/python3.6 /opt  0.2  1.6
 5534 /opt/py3/bin/python3.6 /opt  0.2  1.6
 5562 /opt/py3/bin/python3.6 /opt  0.0  1.6
 2776 /usr/libexec/mysqld --based  0.1  1.6
 5538 /opt/py3/bin/python3.6 /opt  0.0  1.6
 5556 /opt/py3/bin/python3.6 /opt  0.0  1.5
 5557 /opt/py3/bin/python3.6 /opt  0.0  1.5
。。。。。。

2、编写脚本，使用for和while分别实现192.168.0.0/24网段内，地址是否能够ping通，若ping通则输出"success!"，若ping不通则输出"fail!"

#for循环
[root@localhost ~]# cat for_ping.sh 
#!/bin/bash
NET=192.168.0
for ID in {1..254};do
{
    ping -c1 -W1 $NET.$ID &> /dev/null && echo $NET.$ID "success!" || echo $NET.$ID "fail!"
}&
done
wait


#while循环
[root@localhost ~]# cat while_ping.sh 
#!/bin/bash
NET=192.168.0.
declare -i Id=1
while [ $Id -le 254 ];do
{
        ping -c1 -W1 $NET$Id > /dev/null
        if [ $? -eq 0 ];then
                echo "$NET$Id  success!"
        else
                echo "$NET$Id  fail!"
    fi
} &
    let Id++
done
wait

3、每周的工作日1:30，将/etc备份至/backup目录中，保存的文件名称格式 为“etcbak-yyyy-mm-dd-HH.tar.xz”，其中日期是前一天的时间

[root@localhost ~]# cat etcbackup.sh 
#!/bin/bash

[ -d /backup ] || mkdir /backup 
/usr/bin/tar -JcPf  /backup/etcbak-`date -d -1day +%F-%H`.tar.xz /etc/  > /dev/null


[root@localhost ~]# crontab -l
30 1 * * 1-5 /bin/bash /root/etcbackup.sh

[root@localhost ~]# ll /backup/
总用量 13704
-rw-r--r-- 1 root root 7012436 2月   5 13:48 etcbak-2021-02-04-13.tar.xz
-rw-r--r-- 1 root root 7012436 2月   5 14:00 etcbak-2021-02-04-14.tar.xz

4、工作日时间，每10分钟执行一次磁盘空间检查，一旦发现任何分区利用率高 于80%，就发送邮件报警

#配置邮箱
[root@localhost ~]# cat .mailrc 
set from=1787183478@qq.com
set smtp=smtp.qq.com
set smtp-auth-user=1787183478@qq.com
set smtp-auth-password=pzzxrfltahtudddh
set smtp-auth=login
set ssl-verify=ignore


[root@localhost ~]# cat diskcheck.sh 
#!/bin/bash
WARNING=80
df | sed -En '/^\/dev\/sd/s@^([^ ]+).* ([0-9]+)%.*@\1 \2@p'| while read DEVICE USE;
do
[ $USE -gt $WARNING ] && echo "$DEVICE will be full,USE:$USE" | mail -s "diskfull" 1787183478@qq.com
done

[root@localhost ~]# crontab -l
*/10 * * * 1-5 /bin/bash /root/diskcheck.sh