1、显示统计占用系统内存最多的进程，并排序。
[19:08:53 root@centos7 ~]#ps -eo pid,ppid,cmd,%mem --sort=-%mem | head
PID PPID CMD %MEM
1337 1294 /usr/bin/gnome-shell 7.0
1277 1016 /usr/bin/X :0 -background n 1.6
1004 1 /usr/bin/python2 -Es /usr/s 1.0
1011 1 /usr/sbin/libvirtd 0.9
1445 1294 /usr/libexec/gsd-media-keys 0.8
1486 1294 /usr/libexec/gsd-wacom 0.7
1424 1294 /usr/libexec/gsd-xsettings 0.7
1455 1294 /usr/libexec/gsd-power 0.7
1433 1294 /usr/libexec/gsd-color 0.7
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!"
1)for循环脚本
for((i=1;i<=254;i++));do
for((j=1;j<=254;j++));do
ping -c 1 -w 1 192.168.$i.$j &>/dev/null && echo "ping 192.168.$i.$j is success!" || echo ping "192.168.$i.$j is fail!"
done
done
执行结果
[19:41:51 root@centos7 scripts]#bash ping.sh
ping 192.168.1.1 is success!
ping 192.168.1.2 is fail!
ping 192.168.1.3 is fail!
ping 192.168.1.4 is fail!
ping 192.168.1.5 is fail!
ping 192.168.1.6 is fail!
ping 192.168.1.7 is fail!
ping 192.168.1.8 is fail!
ping 192.168.1.9 is fail!
ping 192.168.1.10 is fail!
ping 192.168.1.11 is fail!
ping 192.168.1.12 is fail!
ping 192.168.1.13 is fail!
ping 192.168.1.14 is fail!
ping 192.168.1.15 is fail!
......
2)while循环脚本
i=1
j=1
while ((i<=254));do
while ((j<=254));do
ping -c 1 -w 1 192.168.$i.$j &>/dev/null && echo "ping 192.168.$i.$j is success!" || echo ping "192.168.$i.$j is fail!"
let j++
done
let i++
done
执行结果
[20:07:26 root@centos7 scripts]#bash while_ping.sh
ping 192.168.1.1 is success!
ping 192.168.1.2 is fail!
ping 192.168.1.3 is fail!
ping 192.168.1.4 is fail!
ping 192.168.1.5 is fail!
ping 192.168.1.6 is fail!
ping 192.168.1.7 is fail!
ping 192.168.1.8 is fail!
ping 192.168.1.9 is fail!
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
[20:24:23 root@centos7 ~]#crontab -e
no crontab for root - using an empty one
30 1 * * 1-5 /usr/bin/tar -Jcf /backup/etcbak-`/usr/bin/date -d yesterday +%F-%H`.tar.xz /etc &>/dev/null
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
先编写磁盘容量检查脚本，脚本如下：
for DISK in `df | awk -F " +|%" '/\/dev\/sd/{print $5}'`;do
if [[ $DISK -gt 80 ]];then
mail -s "Disk capacity alarm" root@localhost < /data/disk_alarm.txt
fi
done
将该脚本执行设置为定时任务
[21:30:21 root@centos7 data]#crontab -e
*/10 * * * 1-5 /usr/bin/bash /data/diskcheck.sh
