1、显示统计占用系统内存最多的进程，并排序。
输入top命令后按shift+m
[root@db01 ~]# top
top - 20:54:39 up 17 days, 6 min, 5 users, load average: 0.00, 0.01, 0.05
Tasks: 212 total, 2 running, 210 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.1 us, 0.1 sy, 0.0 ni, 99.8 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3881808 total, 1852912 free, 1063408 used, 965488 buff/cache
KiB Swap: 4194300 total, 4194300 free, 0 used. 2500688 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14108 root 20 0 1979088 234216 48872 S 0.0 6.0 10:42.50 gnome-shell
1348 mysql 20 0 2447264 140100 10580 S 0.0 3.6 15:39.62 mysqld
14282 root 20 0 1050424 101992 16468 S 0.0 2.6 0:48.66 gnome-soft+
14271 root 20 0 1100664 65072 20304 S 0.0 1.7 0:00.64 evolution-+
14445 root 20 0 1122012 61016 18828 S 0.0 1.6 0:00.22 evolution-+
14421 root 20 0 1202692 58940 18784 S 0.0 1.5 0:00.21 evolution-+
15820 root 20 0 940840 54720 21492 S 0.0 1.4 0:01.41 system-con+
14301 root 39 19 805688 50812 8796 S 0.0 1.3 0:01.86 tracker-ex+
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!"
fo语句实现：
#/bin/bash
#
for i in {1..254};do
if ping -W 1 -c 1 192.168.0.$i &> /dev/null; then
echo "192.168.0.$i is up,success!"
else
echo "192.168.0.$i is down,failed!"
fi
done
[root@db01 scripts]# bash -n fping.sh
[root@db01 scripts]# bash fping.sh
192.168.0.1 is down,failed!
192.168.0.2 is down,failed!
192.168.0.3 is up,success!
192.168.0.4 is down,failed!
while实现：
#/bin/bash
#
declare -i i=1
while [ $i -le 254 ];do
if ping -W 1 -c 1 192.168.0.$i &> /dev/null; then
echo "192.168.0.$i is up,success!"
else
echo "192.168.0.$i is down,failed!"
fi
let i++
done
[root@db01 scripts]# bash -n wping.sh
[root@db01 scripts]# bash wping.sh
192.168.0.1 is down,failed!
192.168.0.2 is down,failed!
192.168.0.3 is up,success!
192.168.0.4 is down,failed!
192.168.0.5 is up,success!
192.168.0.6 is down,failed!
192.168.0.7 is down,failed!
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
1 编写备份脚本： 2 3 [root@db01 backup]# ls 4 [root@db01 backup]# cd ~/scripts/ 5 [root@db01 scripts]# vim backup.sh 6 7 #!/bin/bash 8 # 9 10 tar -Jcf /backup/etcbak-`date -d "1 day ago" +"%F-%H"`.tar.xz /etc 11 12 执行脚本测试： 13 14 [root@db01 scripts]# bash backup.sh 15 tar: Removing leading `/' from member names 16 [root@db01 scripts]# cd /backup/ 17 [root@db01 backup]# ls 18 etcbak-2020-02-13-20.tar.xz 19 20 [root@db01 backup]# rm etcbak-2020-02-13-20.tar.xz 21 rm: remove regular file ‘etcbak-2020-02-13-20.tar.xz’? y 22 23 编写计划任务： 24 25 [root@db01 backup]# crontab -e 26 27 [root@db01 backup]# crontab -l 28 30 1 * * 1-5 /usr/bin/bash ~/scripts/backup.sh
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
1 编写检查脚本，并发邮件。
2
3 [root@db01 scripts]# vim diskcheck.sh
4 #!/bin/bash
5 #
6
7 DISK=`df -TPh|awk '+$6>80 {print $1}'|tail -1`
8 if [ ! -z $DISK ];then
9 echo "The part : $DISK will be full,please check !" | mail -s DISK WARNNING' root
10 fi
11
12 测试脚本，本次测试磁盘使用率告警阈值为15%：
13
14 [root@db01 backup]# bash ~/scripts/diskcheck.sh
15 [root@db01 backup]# mail
16 Heirloom Mail version 12.5 7/5/10. Type ? for help.
17 "/var/spool/mail/root": 23 messages 2 new 6 unread
18 U 21 root Fri Feb 14 20:28 19/629 "DISK WARNNING"
19 >N 22 root Fri Feb 14 20:32 18/619 "DISK WARNNING"
20 N 23 root Fri Feb 14 20:32 18/619 "DISK WARNNING"
21 & 23
22 Message 23:
23 From root@db01.localdomain Fri Feb 14 20:32:33 2020
24 Return-Path: <root@db01.localdomain>
25 X-Original-To: root
26 Delivered-To: root@db01.localdomain
27 Date: Fri, 14 Feb 2020 20:32:33 +0800
28 To: root@db01.localdomain
29 Subject: DISK WARNNING
30 User-Agent: Heirloom mailx 12.5 7/5/10
31 Content-Type: text/plain; charset=us-ascii
32 From: root@db01.localdomain (root)
33 Status: R
34
35 The part : /dev/sda1 will be full,please check !
36
37 编写计划任务：
38
39 [root@db01 backup]# crontab -e
40 [root@db01 backup]# crontab -l
41 */10 * * * 1-5 /usr/bin/bash ~/scripts/diskcheck.sh
来源：https://www.cnblogs.com/mark-dq/p/12173480.html