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[#]: subject: (How to use the Linux anacron command)
[#]: via: (https://opensource.com/article/21/2/linux-automation)
[#]: author: (Seth Kenlon https://opensource.com/users/seth)
[#]: collector: (lujun9972)
[#]: translator: (wxy)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
How to use the Linux anacron command
======
Instead of manually performing repetitive tasks, let Linux do them for
you.
![Command line prompt][1]
In 2021, there are more reasons why people love Linux than ever before. In this series, I'll share 21 different reasons to use Linux. Automation is one of the best reasons to use Linux.
One of my favorite things about Linux is its willingness to do work for me. Instead of performing repetitive tasks that eat up my time, or are prone to error, or that I'm likely to forget, I schedule Linux to do them for me.
### Preparing for automation
The term "automation" can be as intimidating as it is appealing. I find it helps to approach it modularly.
#### 1\. What do you want to make happen?
First, know what outcome you want to produce. Are you watermarking images? Removing files from a cluttered directory? Performing a backup of important data? Define the task clearly for yourself so that you know what to aim for. If there's any task you find yourself doing every day, much less more than once a day, then it could be a candidate for automation.
#### 2\. Learn the applications you need
Break down big tasks into small components and learn how to produce each result manually but in a repeatable and predictable way. Much of what can be done on Linux can be scripted, but it's important to recognize your current limitations. There's a world of difference between learning how to automate resizing several images so that they can be emailed conveniently vs. using machine learning to generate elaborate artwork for your weekly newsletter. One of these things you can learn in an afternoon and the other could take years. However, we all have to start somewhere, so just start small and always be on the lookout for ways to improve.
#### 3\. Automate it
Use an automation tool on Linux to make it happen on a regular basis. This is the step this article covers!
To automate something, you need a script that automates a task. When testing, it's best to keep things simple, so the task this article automates is the creation of a file called `hello` in the `/tmp` directory:
```
#!/bin/sh
touch /tmp/hello
```
Copy and paste that simple script into a text file and name it `example`.
### Cron
The built-in automation solution that every Linux install comes with is the cron system. Linux users tend to refer to cron generically as the method you use to schedule a task (usually called a "cron job"), but there are multiple applications that provide cron's functionality. The most versatile is [cronie][2]; its advantage is that it does _not_ assume that your computer is always on, the way historical cron applications designed for system administrators do.
Verify which cron system your Linux distribution provides. If it's anything other than cronie, you can probably install cronie from your distro's software repository. If your distribution doesn't have a package for cronie, you can use the old `anacron` package instead. The `anacron` command is included with cronie, so regardless of how you acquire it, you want to ensure that you have the `anacron` command available on your system before continuing. Anacron may require administrative root privileges, depending on your setup.
```
$ which anacron
/usr/sbin/anacron
```
Anacron's job is to ensure that your automation jobs are executed on a regular basis. To do this, anacron checks to find out when the last time a job ran and then checks how often you have told it to run jobs.
Suppose you set anacron to run a script once every five days. Every time you turn your computer on or wake it from sleep, anacron scans its logs to determine whether it needs to run the job. If a job ran five or more days ago, then anacron runs the job.
### Cron jobs
Many Linux systems come bundled with a few maintenance jobs for cron to perform. I like to keep my jobs separate from the system jobs, so I create a directory in my home directory. Specifically, there's a hidden folder called `~/.local` ("local" in the sense that it's customized for your user account rather than for your "global" computer system), so I create the subdirectory `etc/cron.daily` to mirror cron's usual home on my system. You must also create a spool directory to keep track of the last time jobs were run.
```
`$ mkdir -p ~/.local/etc/cron.daily ~/.var/spool/anacron`
```
You can place any script you want to run regularly into the `~/.local/etc/cron.daily` directory. Copy the `example` script into the directory now, and [mark it executable using the chmod command][3].
```
$ cp example ~/.local/etc/cron.daily
# chmod +x ~/.local/etc/cron.daily/example
```
Next, set up anacron to run whatever scripts are located in the `~/.local/etc/cron.daily` directory.
### Anacron
By default, much of the cron system is considered the systems administrator's domain because it's often used for important low-level tasks, like rotating log files and updating certificates. The configuration demonstrated in this article is designed for a regular user setting up personal automation tasks.
To configure anacron to run your cron jobs, create a configuration file at `/.local/etc/anacrontab`:
```
SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
1  0  cron.mine    run-parts /home/tux/.local/etc/cron.daily/
```
This file tells anacron to run all executable scripts (`run-parts`) found in `~/.local/etc/cron.daily` every one day (that is, daily), with a zero-minute delay. Sometimes, a few minutes' delay is used so that your computer isn't hit with all the possible tasks right after you log in. These settings are suitable for testing, though.
The `cron.mine` value is an arbitrary name for the process. I call it `cron.mine` but you could call it `cron.personal` or `penguin` or anything you want.
Verify your `anacrontab` file's syntax:
```
$ anacron -T -t ~/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
Silence means success.
### Adding anacron to .profile
Finally, you must ensure that anacron runs with your local configuration. Because you're running anacron as a regular user and not as the root user, you must direct it to your local configurations —the `anacrontab` file telling anacron what to do, and the spool directory helping anacron keep track of how many days it's been since each job was last executed:
```
anacron -fn -t /home/tux/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
The `-fn` options tell anacron to _ignore_ timestamps, meaning that you're forcing it to run your cron job no matter what. This is exclusively for testing purposes.
### Testing your cron job
Now that everything's set up, you can test the job. You can technically test this without rebooting, but it makes the most sense to reboot because that's what this is designed to handle: interrupted and irregular login sessions. Take a moment to reboot your computer, log in, and then look for the test file:
```
$ ls /tmp/hello
/tmp/hello
```
Assuming the file exists, your example script has executed successfully. You can now remove the test options from `~/.profile`, leaving this as your final configuration:
```
anacron -t /home/tux/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
### Using anacron
You have your personal automation infrastructure configured, so you can place any script you want your computer to manage for you into the `~/.local/etc/cron.daily` directory and it will run as scheduled.
It's up to you how often you want jobs to run. Your example script is executed once a day. Obviously, that depends on whether your computer is powered on and awake on any given day. If you use your computer on Friday but set it aside for the weekend, the script won't run on Saturday and Sunday. However, on Monday the script will execute because anacron will know that at least one day has passed. You can add weekly, fortnightly, or even monthly directories to `~/.local/etc` to schedule a wide variety of intervals.
To add a new interval:
1. Add a directory to `~/.local/etc` (for instance, `cron.weekly`).
2. Add a line to `~/.local/etc/anacrontab` to run scripts in the new directory. For a weekly interval, the configuration would be: [code]`7 0 cron.mine run-parts /home/tux/.local/etc/cron.weekly/`[/code] (with the `0` value optionally being some number of minutes to politely delay the start of the script).
3. Place your scripts in the `cron.weekly` directory.
Welcome to the automated lifestyle. It won't feel like it, but you're about to become a lot more productive.
--------------------------------------------------------------------------------
via: https://opensource.com/article/21/2/linux-automation
作者：[Seth Kenlon][a]
选题：[lujun9972][b]
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://opensource.com/users/seth
[b]: https://github.com/lujun9972
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/command_line_prompt.png?itok=wbGiJ_yg (Command line prompt)
[2]: https://github.com/cronie-crond/cronie
[3]: https://opensource.com/article/19/8/linux-chmod-command

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@ -0,0 +1,160 @@
[#]: subject: (How to use the Linux anacron command)
[#]: via: (https://opensource.com/article/21/2/linux-automation)
[#]: author: (Seth Kenlon https://opensource.com/users/seth)
[#]: collector: (lujun9972)
[#]: translator: (wxy)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
如何使用 Linux anacron 命令
======
> 与其手动执行重复性的任务，不如让 Linux 为你做。
![命令行提示][1]
在 2021 年，人们有更多的理由喜欢 Linux。在这个系列中，我将分享使用 Linux 的 21 个不同理由。自动化是使用 Linux 的最佳理由之一。
我最喜欢 Linux 的一个原因是它愿意为我做工作。我不需要执行重复性的任务，这些任务会占用我的时间，或者容易出错，或者我可能会忘记，我安排 Linux 为我做这些工作。
### 为自动化做准备
“自动化”这个词既让人望而生畏，又让人心动。我发现用模块化的方式来处理它是有帮助的。
#### 1、你想实现什么？
首先，要知道你想产生什么结果。你是要给图片加水印吗？从杂乱的目录中删除文件？执行重要数据的备份？为自己明确定义任务，这样你就知道自己的目标是什么。如果有什么任务你发现自己每天都在做，甚至一天一次以上，那么它可能是自动化的候选者。
#### 2、学习你需要的应用
将大的任务分解成小的组件，并学习如何手动但以可重复和可预测的方式产生每个结果。在 Linux 上可以做的很多事情都可以用脚本来完成，但重要的是要认识到你当前的局限性。学习如何自动调整几张图片的大小，以便可以方便地通过电子邮件发送，与使用机器学习为你的每周通讯生成精心制作的艺术品之间有天壤之别。其中一件事你可以在一个下午学会，而另一件事可能要花上几年时间。然而，我们都必须从某个地方开始，所以只要从小做起，并时刻注意改进的方法。
#### 3、自动化
在 Linux 上使用一个自动化工具来定期实现它。这就是本文介绍的步骤!
要想自动化一些东西，你需要一个脚本来自动化一个任务。在测试时，最好保持简单，所以本文自动化的任务是在 `/tmp` 目录下创建一个名为 `hello` 的文件。
```
#!/bin/sh
touch /tmp/hello
```
将这个简单的脚本复制并粘贴到一个文本文件中，并将其命名为 `example`。
### Cron
每个 Linux 安装都会有的内置自动化解决方案就是 cron 系统。Linux 用户往往把 cron 笼统地称为你用来安排任务的方法（通常称为 “cron 作业”），但有多个应用程序可以提供 cron 的功能。最通用的是 [cronie][2]；它的优点是，它不会像历史上为系统管理员设计的 cron 应用程序那样，假设你的计算机总是开着。
验证你的 Linux 发行版提供的是哪个 cron 系统。如果不是 cronie，你可以从发行版的软件仓库中安装 cronie。如果你的发行版没有 cronie 的软件包，你可以使用旧的 anacron 软件包来代替。`anacron` 命令是包含在 cronie 中的，所以不管你是如何获得它的，你都要确保在你的系统上有 `anacron` 命令，然后再继续。anacron 可能需要管理员 root 权限，这取决于你的设置。
```
$ which anacron
/usr/sbin/anacron
```
anacron 的工作是确保你的自动化作业定期执行。为了做到这一点，anacron 会检查找出最后一次运行作业的时间，然后检查你告诉它运行作业的频率。
假设你将 anacron 设置为每五天运行一次脚本。每次你打开电脑或从睡眠中唤醒电脑时，anacron都会扫描其日志以确定是否需要运行作业。如果一个作业在五天或更久之前运行，那么 anacron 就会运行该作业。
### Cron 作业
许多 Linux 系统都捆绑了一些维护工作，让 cron 来执行。我喜欢把我的工作与系统工作分开，所以我在我的主目录中创建了一个目录。具体来说，有一个叫做 `~/.local` 的隐藏文件夹（“local” 的意思是它是为你的用户账户定制的，而不是为你的“全局”计算机系统定制的），所以我创建了子目录 `etc/cron.daily` 来镜像 cron 在我的系统上通常的家目录。你还必须创建一个 spool 目录来跟踪上次运行作业的时间。
```
$ mkdir -p ~/.local/etc/cron.daily ~/.var/spool/anacron
```
你可以把任何你想定期运行的脚本放到 `~/.local/etc/cron.daily` 目录中。现在把 `example` 脚本复制到目录中，然后 [用 chmod 命令使其可执行][3]。
```
$ cp example ~/.local/etc/cron.daily
# chmod +x ~/.local/etc/cron.daily/example
```
接下来，设置 anacron 来运行位于 `~/.local/etc/cron.daily` 目录下的任何脚本。
### anacron
默认情况下，cron 系统的大部分内容都被认为是系统管理员的领域，因为它通常用于重要的低层任务，如轮换日志文件和更新证书。本文演示的配置是为普通用户设置个人自动化任务而设计的。
要配置 anacron 来运行你的 cron 作业，请在 `/.local/etc/anacrontab` 创建一个配置文件：
```
SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
1  0  cron.mine    run-parts /home/tux/.local/etc/cron.daily/
```
这个文件告诉 anacron 每到新的一天（也就是是每日），延迟 0 分钟，就运行（`run-parts`）所有在 `~/.local/etc/cron.daily` 中找到的可执行脚本。有时，会使用几分钟的延迟，这样你的计算机就不会在你登录后就被所有可能的任务冲击。不过这些设置适合测试。
`cron.mine` 值是进程的一个任意名称。我称它为 `cron.mine`，但你也可以称它为 `cron.personal` 或 `penguin` 或任何你想要的名字。
验证你的 `anacrontab` 文件的语法：
```
$ anacron -T -t ~/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
沉默意味着成功。
### 在 .profile 中添加 anacron
最后，你必须确保 anacron 以你的本地配置运行。因为你是以普通用户而不是 root 用户的身份运行 anacron，所以你必须将它引导到你的本地配置：告诉 anacron 要做什么的 `anacrontab` 文件，以及帮助 anacron 跟踪每一个作业最后一次执行是多少天的 spool 目录：
```
anacron -fn -t /home/tux/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
`-fn` 选项告诉 anacron *忽略* 时间戳，这意味着你强迫它无论如何都要运行你的 cron 工作。这完全是为了测试的目的。
### 测试你的 cron 作业
现在一切都设置好了，你可以测试作业了。从技术上讲，你可以在不重启的情况下进行测试，但重启是最有意义的，因为这就是设计用来处理：中断和不规则的登录会话。花点时间重启电脑、登录，然后寻找测试文件：
```
$ ls /tmp/hello
/tmp/hello
```
假设文件存在，那么你的示例脚本已经成功执行。现在你可以从 `~/.profile` 中删除测试选项，留下这个作为你的最终配置。
```
anacron -t /home/tux/.local/etc/anacrontab \
-S /home/tux/.var/spool/anacron
```
### 使用 anacron
你已经配置好了你的个人自动化基础设施，所以你可以把任何你想让你的计算机替你管理的脚本放到 `~/.local/etc/cron.daily` 目录下，它就会按计划运行。
这取决于你希望作业运行的频率。你的示例脚本是每天执行一次。很明显，这取决于你的计算机在任何一天是否开机和醒着。如果你在周五使用电脑，但把它设置在周末，脚本就不会在周六和周日运行。然而，在周一，脚本会执行，因为 anacron 会知道至少有一天已经过去了。你可以在 `~/.local/etc` 中添加每周、每两周、甚至每月的目录，以安排各种各样的间隔。
要添加一个新的时间间隔：
1. 在 `~/.local/etc` 中添加一个目录（例如 `cron.weekly`）。
2. 在 `~/.local/etc/anacrontab` 中添加一行，以便在新目录下运行脚本。对于每周一次的间隔，其配置如下。`7 0 cron.mine run-parts /home/tux/.local/etc/cron.weekly/`（`0` 的值可以选择一些分钟数，以适当地延迟脚本的启动）。
3. 把你的脚本放在 `cron.weekly` 目录下。
欢迎来到自动化的生活方式。它不会让人感觉到，但你将会变得更有效率。
--------------------------------------------------------------------------------
via: https://opensource.com/article/21/2/linux-automation
作者：[Seth Kenlon][a]
选题：[lujun9972][b]
译者：[wxy](https://github.com/wxy)
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://opensource.com/users/seth
[b]: https://github.com/lujun9972
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/command_line_prompt.png?itok=wbGiJ_yg (Command line prompt)
[2]: https://github.com/cronie-crond/cronie
[3]: https://opensource.com/article/19/8/linux-chmod-command