Crontab 关闭命令不起作用

Question

我希望 Crontab 每天关闭系统，但它没有这样做，我是不是拼错了什么？这是我的 Crontab 文件：

 /etc/crontab: system-wide crontab
 Unlike any other crontab you don't have to run the `crontab'
 command to install the new version when you edit this file
 and files in /etc/cron.d. These files also have username fields,
 that none of the other crontabs do.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

 m h dom mon dow user   command
17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly
25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

每天凌晨 02:30 关闭

30 0 2 * * * /sbin/shutdown -h now

---

没关系，但我对 Ubuntu 有点陌生，所以我在终端中打开了 Crontab -e，它看起来像这样：

# Edit this file to introduce tasks to be run by cron.

# Each task to run has to be defined through a single line indicating with
# different fields when the task will be run and what command to run for the
# task. To define the time you can provide concrete values for minute (m), 
# hour (h), day of month (dom), month (mon), and day of week (dow) or use 
# '*' in these fields (for 'any').

# Notice that tasks will be started based on the cron's system daemon's 
# notion of time and timezones. Output of the crontab jobs (including 
# errors) is sent through email to the user the crontab file belongs to 
# (unless redirected).

# For example, you can run a backup of all your user accounts at 5 a.m 
# every week with:

# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/

# For more information see the manual pages of crontab(5) and cron(8)

# m h dom mon dow command
30 02 * /sbin/shutdown -h now

所以我应该在最后输入我的命令还是如何输入？以及如何保存它，因为我很困惑。

Answer 1

您配置了crontab错误的 do 如下：

1. 在终端类型中：

   sudo crontab -e
   

2. 然后给出它的条目，如：

   30 02 * * * /sbin/shutdown -h now