24-Linux核心知识-定时任务补充-磁盘管理-上部

定时任务中-命令或脚本结果（正确及错误）定向到黑洞（>/dev/null 2>&1)或追加到文件中  >>/tmp/exam.txt 2>&1

/dev/null   黑洞

不记录任何信息  >/dev/null 2>&1               ====  1>/dev/null  2>/dev/null

记录执行过程     >>/tmp/exam.txt   2>&1    === >>/tmp/exam.txt 2>>/tmp/exam.txt

 

[root@manager ~]# crontab -l
#sync time ntp
*/2 * * * * /usr/sbin/ntpdate ntp1.aliyun.com           >/dev/null 2>&1
#print name to file by yuyu at 2018********
#* * * * * /bin/echo exam                               >>/exam/exam.txt        2>&1
#backup etc dir
#00 00 * * *  /bin/sh /server/scripts/bak.sh            >/dev/null 2>&1
#print time
#* * * * * date +\%F                                    >>/tmp/time.log         2>&1
#backup ser
#00 */2 * * * sh /server/scripts/bak-ser.sh             >/dev/null 2>&1

* * * * * echo exam.com

 

[root@manager ~]# systemctl stop postfix.service
[root@manager ~]# systemctl disable postfix.service
Removed symlink /etc/systemd/system/multi-user.target.wants/postfix.service.
[root@manager ~]# systemctl status postfix.service
● postfix.service - Postfix Mail Transport Agent
   Loaded: loaded (/usr/lib/systemd/system/postfix.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Fri 2019-12-13 18:03:44 CST; 16min ago

Dec 13 18:03:42 manager systemd[1]: Starting Postfix Mail Transport Agent...
Dec 13 18:03:42 manager aliasesdb[808]: /usr/sbin/postconf: fatal: parameter inet_interfaces: no local interface found for ::1
Dec 13 18:03:43 manager aliasesdb[808]: newaliases: fatal: parameter inet_interfaces: no local interface found for ::1
Dec 13 18:03:43 manager postfix/sendmail[1169]: fatal: parameter inet_interfaces: no local interface found for ::1
Dec 13 18:03:43 manager postfix[1178]: fatal: parameter inet_interfaces: no local interface found for ::1
Dec 13 18:03:44 manager systemd[1]: postfix.service: control process exited, code=exited status=1
Dec 13 18:03:44 manager systemd[1]: Failed to start Postfix Mail Transport Agent.
Dec 13 18:03:44 manager systemd[1]: Unit postfix.service entered failed state.
Dec 13 18:03:44 manager systemd[1]: postfix.service failed.

 

没有定向到空案例

【企业案例】如果定时任务规则结尾不加>/dev/null 2>&1 或者追加到文件中 >>/tmp/exam 2>&1,  很容易导致硬盘 inode 空间被占满，从而系统服务不正常。

 

定时任务不断给你发邮件

1、邮件服务关闭

systemctl stop postfix.service

systemctl disable postfix.service

2、临时存放起来  /var/spool/postfix/maildrop

 

定时任务中命令或脚本的结果，没有定向到空或文件中

1、邮件的软件没有开启---------大量小文件堆积在 /var/spool/postfix/maildrop/ --------inode 满了

2、邮件软件开启了 --------------定时任务会不断的给root 用户发邮件

you have new mail in /var/spool/mail/root

 

[root@manager ~]# cat /server/scripts/bak-etc.sh 
p=$(hostname -I|awk '{print $1}')
mkdir -p /backup/$ip
tar zchf /backup/$ip/conf -$(date +%F).tar.gz /etc/rc.local /etc/fstab

[root@manager ~]# cat /server/scripts/ip.sh 
. /etc/profile
ipconfig eth0 |awk 'NR==2{print $2}'
date