mirror of
https://github.com/LCTT/TranslateProject.git
synced 2025-01-16 22:42:21 +08:00
Ezio
GitHub
commit
0ca6bfc3b1
@ -1,180 +0,0 @@
|
||||
Translating by Ping
|
||||
|
||||
How to Add Cron Jobs in Linux and Unix
|
||||
======================================
|
||||
|
||||
|
||||
|
||||
|
||||
### Introduction
|
||||
|
||||
|
||||
|
||||
Cron job are used to schedule commands to be executed periodically. You can setup commands or scripts, which will repeatedly run at a set time. Cron is one of the most useful tool in Linux or UNIX like operating systems. The cron service (daemon) runs in the background and constantly checks the /etc/crontab file, and /etc/cron.*/ directories. It also checks the /var/spool/cron/ directory.
|
||||
|
||||
### Command of crontab
|
||||
|
||||
crontab is the command used to install, deinstall or list the tables (cron configuration file) used to drive the [cron(8)][1] daemon in Vixie Cron. Each user can have their own crontab file, and though these are files in /var/spool/cron/crontabs, they are not intended to be edited directly. You need to use crontab command for editing or setting up your own cron jobs.
|
||||
|
||||
### Types of cron configuration files
|
||||
|
||||
There are different types of configuration files:
|
||||
|
||||
- **The UNIX / Linux system crontab** : Usually, used by system services and critical jobs that requires root like privileges. The sixth field (see below for field description) is the name of a user for the command to run as. This gives the system crontab the ability to run commands as any user.
|
||||
|
||||
- **The user crontabs**: User can install their own cron jobs using the crontab command. The sixth field is the command to run, and all commands run as the user who created the crontab
|
||||
|
||||
**Note**: This faq features cron implementations written by Paul Vixie and included in many [Linux][2] distributions and Unix like systems such as in the popular 4th BSD edition. The syntax is [compatible][3] with various implementations of crond.
|
||||
|
||||
How Do I install or create or edit my own cron jobs?
|
||||
|
||||
To edit your crontab file, type the following command at the UNIX / Linux shell prompt:
|
||||
|
||||
```
|
||||
$ crontab -e
|
||||
```
|
||||
|
||||
Syntax of crontab (field description)
|
||||
|
||||
The syntax is:
|
||||
|
||||
```
|
||||
1 2 3 4 5 /path/to/command arg1 arg2
|
||||
```
|
||||
|
||||
OR
|
||||
|
||||
```
|
||||
1 2 3 4 5 /root/ntp_sync.sh
|
||||
```
|
||||
|
||||
Where,
|
||||
|
||||
- 1: Minute (0-59)
|
||||
- 2: Hours (0-23)
|
||||
- 3: Day (0-31)
|
||||
- 4: Month (0-12 [12 == December])
|
||||
- 5: Day of the week(0-7 [7 or 0 == sunday])
|
||||
- /path/to/command – Script or command name to schedule
|
||||
|
||||
Easy to remember format:
|
||||
|
||||
```
|
||||
* * * * * command to be executed
|
||||
– – – – –
|
||||
| | | | |
|
||||
| | | | —– Day of week (0 – 7) (Sunday=0 or 7)
|
||||
| | | ——- Month (1 – 12)
|
||||
| | ——— Day of month (1 – 31)
|
||||
| ———– Hour (0 – 23)
|
||||
————- Minute (0 – 59)
|
||||
```
|
||||
|
||||
Example simple crontab.
|
||||
|
||||
````
|
||||
## run backupscript 5 minutes 1 time ##
|
||||
*/5 * * * * /root/backupscript.sh
|
||||
|
||||
## Run backupscript daily on 1:00 am ##
|
||||
|
||||
0 1 * * * /root/backupscript.sh
|
||||
|
||||
## Run backup script monthly on the 1st of month 3:15 am ##
|
||||
|
||||
15 3 1 * * /root/backupscript.sh
|
||||
```
|
||||
|
||||
### How do I use operators?
|
||||
|
||||
An operator allows you to specifying multiple values in a field. There are three operators:
|
||||
|
||||
- **The asterisk (*)** : This operator specifies all possible values for a field. For example, an asterisk in the hour time field would be equivalent to every hour or an asterisk in the month field would be equivalent to every month
|
||||
|
||||
- **The comma (,)** : This operator specifies a list of values, for example: “1,5,10,15,20, 25”.
|
||||
|
||||
- **The dash (–)** : This operator specifies a range of values, for example: “5-15” days , which is equivalent to typing “5,6,7,8,9,….,13,14,15” using the comma operator.
|
||||
|
||||
- **The separator (/)** : This operator specifies a step value, for example: “0-23/” can be used in the hours field to specify command execution every other hour. Steps are also permitted after an asterisk, so if you want to say every two hours, just use */2.
|
||||
|
||||
|
||||
### Use special string to save time
|
||||
|
||||
Instead of the first five fields, you can use any one of eight special strings. It will not just save your time but it will improve readability.
|
||||
|
||||
Special string | Meaning
|
||||
|:-- |:--
|
||||
@reboot | Run once, at startup.
|
||||
@yearly | Run once a year, “0 0 1 1 *”.
|
||||
@annually | (same as @yearly)
|
||||
@monthly | Run once a month, “0 0 1 * *”.
|
||||
@weekly | Run once a week, “0 0 * * 0”.
|
||||
@daily | Run once a day, “0 0 * * *”.
|
||||
@midnight | (same as @daily)
|
||||
@hourly | Run once an hour, “0 * * * *”.
|
||||
|
||||
|
||||
Examples
|
||||
|
||||
```
|
||||
#### Run ntpdate command every hour ####
|
||||
|
||||
@hourly /path/to/ntpdate
|
||||
```
|
||||
|
||||
|
||||
### More about /etc/crontab file and /etc/cron.d/* directories
|
||||
|
||||
/etc/crontab is system crontabs file. Usually only used by root user or daemons to configure system wide jobs. All individual user must must use crontab command to install and edit their jobs as described above. /var/spool/cron/ or /var/cron/tabs/ is directory for personal user crontab files. It must be backup with users home directory.
|
||||
|
||||
Understanding Default /etc/crontab
|
||||
|
||||
Typical /etc/crontab file entries:
|
||||
|
||||
```
|
||||
SHELL=/bin/bash
|
||||
PATH=/sbin:/bin:/usr/sbin:/usr/bin
|
||||
MAILTO=root
|
||||
HOME=/
|
||||
# run-parts
|
||||
01 * * * * root run-parts /etc/cron.hourly
|
||||
02 4 * * * root run-parts /etc/cron.daily
|
||||
22 4 * * 0 root run-parts /etc/cron.weekly
|
||||
42 4 1 * * root run-parts /etc/cron.monthly
|
||||
```
|
||||
|
||||
First, the environment must be defined. If the shell line is omitted, cron will use the default, which is sh. If the PATH variable is omitted, no default will be used and file locations will need to be absolute. If HOME is omitted, cron will use the invoking users home directory.
|
||||
|
||||
Additionally, cron reads the files in /etc/cron.d/ directory. Usually system daemon such as sa-update or sysstat places their cronjob here. As a root user or superuser you can use following directories to configure cron jobs. You can directly drop your scripts here. The run-parts command run scripts or programs in a directory via /etc/crontab file:
|
||||
|
||||
Directory |Description
|
||||
|:-- |:--
|
||||
/etc/cron.d/ | Put all scripts here and call them from /etc/crontab file.
|
||||
/etc/cron.daily/ | Run all scripts once a day
|
||||
/etc/cron.hourly/ | Run all scripts once an hour
|
||||
/etc/cron.monthly/ | Run all scripts once a month
|
||||
/etc/cron.weekly/ | Run all scripts once a week
|
||||
|
||||
|
||||
### Backup cronjob
|
||||
|
||||
```
|
||||
# crontab -l > /path/to/file
|
||||
|
||||
# crontab -u user -l > /path/to/file
|
||||
```
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.unixmen.com/add-cron-jobs-linux-unix/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+unixmenhowtos+%28Unixmen+Howtos+%26+Tutorials%29
|
||||
|
||||
作者：[Duy NguyenViet][a]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.unixmen.com/author/duynv/
|
||||
[1]: http://www.manpager.com/linux/man8/cron.8.html
|
||||
[2]: http://www.linuxsecrets.com/
|
||||
[3]: http://www.linuxsecrets.com/linux-hardware/
|
||||
@ -0,0 +1,183 @@
|
||||
如何在Linux及Unix系统中添加定时任务
|
||||
======================================
|
||||
|
||||
|
||||
|
||||
|
||||
### 导言
|
||||
|
||||
|
||||
|
||||
定时任务是用来定期执行计划命令的。你可以将命令组织到脚本当中，这样就可以在设定的时间将其重复执行。`Cron`是Linux系统或者类Unix系统当中最为实用的工具之一。定时服务（守护进程）在系统后台运行，并且会持续地检查 /etc/crontab 文件和 /etc/cron.*/ 目录。它同样也会检测 /var/spool/cron/ 目录。
|
||||
|
||||
|
||||
### crontab 命令
|
||||
|
||||
`crontab`是用来安装、卸载或者列出定时配置文件列表的命令。定时配置文件则用于驱动`Vixie Cron`的[cron(8)][1]守护进程。每个用户都可以拥有自己的 crontab 文件，虽然这些文件位于 /var/spool/cron/crontabs 目录中，但这并不意味着你可以直接编辑它们。你需要通过`crontab`命令来编辑或者配置自己的定时任务。
|
||||
|
||||
|
||||
### 定时配置文件的类型
|
||||
|
||||
配置文件分为以下不同的类型：
|
||||
|
||||
- **UNIX 或 Linux 系统的 crontab** : 此类型通常由类似需要root权限的系统服务或重要任务使用。第六个字段（见下方的字段介绍）为用户名，用来指定此命令以哪个用户身份来执行。如此一来，系统的`crontab`就能够以任意用户的身份来执行操作。
|
||||
|
||||
- **用户的 crontabs**: 用户可以使用`corntab`命令来安装属于他们自己的定时任务。 第六个字段为需要运行的命令行, 所有的命令行都会以创建 crontab 的用户的身份运行。
|
||||
|
||||
**Note**: This faq features cron implementations written by Paul Vixie and included in many [Linux][2] distributions and Unix like systems such as in the popular 4th BSD edition. The syntax is [compatible][3] with various implementations of crond.
|
||||
|
||||
**注意**: 这种问答形式的`Cron`实现是由 Paul Vixie 所写的，并且被许多 [Linux][2] 发行版和类Unix系统（如广受欢迎的第四版BSD）包含其中。它的语法被各种计划任务的实现所[兼容][3]。
|
||||
|
||||
该如何安装、创建或编辑我们自己的定时任务呢？
|
||||
|
||||
在 Linux 或 Unix 的shell提示符后键入以下命令来编辑你的 crontab 文件。
|
||||
|
||||
```
|
||||
$ crontab -e
|
||||
```
|
||||
|
||||
`crontab`语法（字段介绍）：
|
||||
|
||||
语法为：
|
||||
|
||||
```
|
||||
1 2 3 4 5 /path/to/command arg1 arg2
|
||||
```
|
||||
|
||||
或者
|
||||
|
||||
```
|
||||
1 2 3 4 5 /root/ntp_sync.sh
|
||||
```
|
||||
|
||||
说明：
|
||||
|
||||
- 1: 分钟 (0-59)
|
||||
- 2: 小时 (0-23)
|
||||
- 3: 日期 (0-31)
|
||||
- 4: 月份 (0-12 [12 == December])
|
||||
- 5: 一周当中的某天 (0-7 [7 或 0 == 周日])
|
||||
- /path/to/command – 计划执行的脚本或命令名
|
||||
|
||||
便于记忆的格式：
|
||||
|
||||
```
|
||||
* * * * * command to be executed
|
||||
– – – – –
|
||||
| | | | |
|
||||
| | | | —– 一周当中的某天 (0 – 7) (周日=0 or 7)
|
||||
| | | ——- 月份 (1 – 12)
|
||||
| | ——— 一月当中的某天 (1 – 31)
|
||||
| ———– 小时 (0 – 23)
|
||||
————- 分钟 (0 – 59)
|
||||
```
|
||||
|
||||
简单的`crontab`示例：
|
||||
|
||||
````
|
||||
## 每隔5分钟运行一次 backupscript 脚本##
|
||||
*/5 * * * * /root/backupscript.sh
|
||||
|
||||
## 每天的上午1:00运行 backupscript 脚本 ##
|
||||
|
||||
0 1 * * * /root/backupscript.sh
|
||||
|
||||
## 每月的第一个上午3:15 运行 backupscript 脚本 ##
|
||||
|
||||
15 3 1 * * /root/backupscript.sh
|
||||
```
|
||||
|
||||
|
||||
### 如何使用操作符
|
||||
|
||||
操作符允许你为一个字段指定多个值，这里有三个操作符可供使用：
|
||||
|
||||
- **星号 (*)** : 此操作符为字段指定所有可用的值。举个例子，在小时字段中，一个星号等同于所有可用的hour值；在月份字段中，一个星号表示所有可用的month值。
|
||||
|
||||
- **逗号 (,)** : 这个操作符指定了一个包含多个值的列表，例如：`1,5,10,15,20, 25`.
|
||||
|
||||
- **横杠 (–)** : 此操作符指定了一个值的范围，例如：`5-15` 天，等同于使用逗号操作符键入的 `5,6,7,8,9,….,13,14,15`。
|
||||
|
||||
- **分隔符 (/)** : 此操作符指定了一个步进值，例如： `0-23/` 可以用于小时字段来指定命令行每小时执行一次。步进值也可以跟在星号操作符后边，如果你希望命令行每2小时执行一次，可以这样写 `*/2`。
|
||||
|
||||
|
||||
### 使用特殊字符保存时间
|
||||
|
||||
你可以使用以下8个特殊字符中的其中一个替代头五个字段。这样不但可以保存时间，也可以提高可读性。
|
||||
|
||||
特殊字符 | 含义
|
||||
|:-- |:--
|
||||
@reboot | 在每次启动时运行一次
|
||||
@yearly | 每年运行一次, “0 0 1 1 *”.
|
||||
@annually | (同 @yearly)
|
||||
@monthly | 每月运行一次, “0 0 1 * *”.
|
||||
@weekly | 每周运行一次, “0 0 * * 0”.
|
||||
@daily | 每天运行一次, “0 0 * * *”.
|
||||
@midnight | (同 @daily)
|
||||
@hourly | 每小时运行一次, “0 * * * *”.
|
||||
|
||||
|
||||
示例：
|
||||
|
||||
```
|
||||
#### 每小时运行一次 ntpdate ####
|
||||
|
||||
@hourly /path/to/ntpdate
|
||||
```
|
||||
|
||||
|
||||
### 关于 /etc/crontab file 和 /etc/cron.d/* 目录的更多内容
|
||||
|
||||
/etc/crontab 是系统的 corntabs 文件。通常用于root用户和守护进程配置整个系统的任务。每个独立的用户务必遵照以上的介绍，使用`corntab`命令来编辑自己的任务。/var/spool/cron/ 或者 /var/cron/tabs/ 目录存放了个人用户的 corntab 文件，它必定会备份在用户的home目录当中。
|
||||
|
||||
理解默认的 /etc/crontab
|
||||
|
||||
典型的 /etc/crontab 文件内容：
|
||||
|
||||
```
|
||||
SHELL=/bin/bash
|
||||
PATH=/sbin:/bin:/usr/sbin:/usr/bin
|
||||
MAILTO=root
|
||||
HOME=/
|
||||
# run-parts
|
||||
01 * * * * root run-parts /etc/cron.hourly
|
||||
02 4 * * * root run-parts /etc/cron.daily
|
||||
22 4 * * 0 root run-parts /etc/cron.weekly
|
||||
42 4 1 * * root run-parts /etc/cron.monthly
|
||||
```
|
||||
|
||||
首先，环境必须定义好。如果shell行被忽略了，corn会使用默认的sh shell。如果PATH变量被忽略，就没有默认路径会被使用，并且所有的文件都需要使用绝对路径来定位。如果HOME被忽略，corn会将调用者（用户）的home目录作为默认值使用。
|
||||
|
||||
另外，corn 会在/etc/cron.d/ 目录中读取文件。通常情况下，像 sa-update 或者 sysstat 这样的系统守护进程会将他们的定时任务存放在此处。作为root用户或者超级用户，你可以使用以下目录来配置你的定时任务。你可以直接将脚本放到这里。`run-parts`命令会通过 /etc/crontab 目录来运行脚本或者程序。
|
||||
|
||||
目录 |介绍
|
||||
|:-- |:--
|
||||
/etc/cron.d/ | 将所有的脚本文件放在此处，并从 /etc/crontab 文件中调用它们。
|
||||
/etc/cron.daily/ | 每天运行的所有的脚本
|
||||
/etc/cron.hourly/ | 每小时运行的所有脚本
|
||||
/etc/cron.monthly/ | 每月运行的所有脚本
|
||||
/etc/cron.weekly/ | 每周运行的所有脚本
|
||||
|
||||
|
||||
### 备份定时任务
|
||||
|
||||
```
|
||||
# crontab -l > /path/to/file
|
||||
|
||||
# crontab -u user -l > /path/to/file
|
||||
```
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.unixmen.com/add-cron-jobs-linux-unix/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+unixmenhowtos+%28Unixmen+Howtos+%26+Tutorials%29
|
||||
|
||||
作者：[Duy NguyenViet][a]
|
||||
译者：[mr-ping](https://github.com/mr-ping)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.unixmen.com/author/duynv/
|
||||
[1]: http://www.manpager.com/linux/man8/cron.8.html
|
||||
[2]: http://www.linuxsecrets.com/
|
||||
[3]: http://www.linuxsecrets.com/linux-hardware/
|
||||
Loading…
Reference in New Issue
Block a user