【crontab】误删crontab及其恢复

中秋节快到了，首先祝自己中秋快乐。

昨天下午六点，心里正想着加完一个crontab就可以下班了。本来想执行 crontab -e的，没想到手一抖就输入了crontab ，然后就进入了下面这个样子。

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一看不对劲，就随手按了 Ctrl + D。

接下来，恐怖的事情发生了，crontab的所有任务都被清空了。

查找资料发现如下：

如果遗漏了任何选项,crontab可能会打开一个空文件,或者看起来像是个空文件。这时敲delete键退出,不要按<Ctrl-D>,否则你将丢失crontab文件。 

此时我的心情是这样的

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alt="" />

不过，自己删的crontab，跪着也要找回来。

皇天不负苦心人，办法还是有的。crontab有运行日志，在日志里面可以找到执行过的历史命令。前提是要有root权限。

命令如下：

cat /var/log/cron* | grep -i "`which cron`" > ./all_temp

cat  ./all_temp | grep -v "<command>" > ./cmd_temp

用awk读取cmd_temp,即可得到命令。

[script- tmp]$ cat cmd_temp  | grep username | awk -F 'CMD' '{print $2}' | sort | uniq

 (bash   /home/appadmin/script/security/auto_restart.sh)

命令是找回了，可是执行周期呢？还是靠cmd_temp。

[script- tmp]$ cat cmd_temp  | grep /home/appadmin/script/security/auto_restart.sh | head
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)
Sep  :: script- CROND[]: (appadmin) CMD (bash   /home/appadmin/script/security/auto_restart.sh)

可以很明显的看出，命令是一分钟一次。

全部恢复完成后已经是下班后一个小时了。不管怎么样，总算把自己坑填好了。