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This article is about how to use anacron in linux. Xiaobian thinks it is quite practical, so share it with everyone for reference. Let's follow Xiaobian and have a look.

anacron is an asynchronous timed task scheduler, we all know cron is a Linux system under the timed task scheduler, can achieve asynchronous task scheduling. For 24 hours running servers may not need this kind of thing, but non-24 hours boot, but also want to run the task of the machine is still very useful, you can achieve asynchronous calls.

Preparing for automation

The word "automation" is both daunting and exciting. I find it helpful to approach it in a modular way.

1 What do you want to achieve?

First, know what you want to produce. Are you going to watermark the picture? Delete files from cluttered directories? Perform backup of critical data? Define tasks clearly for yourself so you know what your goals are. If there's a task you find yourself doing every day, or even more than once a day, then it might be a candidate for automation.

2. Learn the applications you need

Break large tasks into smaller components and learn how to produce each result manually but in a repeatable and predictable way. There are many things you can do on Linux that can be done with scripts, but it's important to recognize your current limitations. Learning how to automatically resize a few pictures so they can be easily emailed is a far cry from using machine learning to generate elaborate artwork for your weekly newsletter. Some things you can learn in an afternoon, others can take years. However, we all have to start somewhere, so just start small and keep an eye on ways to improve.

3. Automation

Use an automated tool on Linux to implement it periodically. This is the procedure described in this article! To automate something, you need a script to automate a task. When testing, it's best to keep it simple, so the automated task in this article is to create a file called hello in the/tmp directory.

#!/ bin/shtouch /tmp/hello

Copy and paste this simple script into a text file and name it example.

Cron

Every installed Linux system has a built-in automation solution called cron. Linux users tend to refer to cron generically as the method you use to schedule tasks (often referred to as "cron jobs"), but there are multiple applications that provide cron functionality. The most common is cronie; the advantage is that it doesn't assume your computer is always on, like cron applications historically designed for system administrators.

Verify which cron system your Linux distribution provides. If not cronie, you can install cronie from the distribution repository. If your distribution doesn't have cronie packages, you can use older anacron packages instead. The anacron command is included in cronie, so no matter how you get it, make sure you have the anacron command on your system before proceeding. Anacron may require administrator root privileges, depending on your settings.

$ which anacron/usr/sbin/anacron

Anacron's job is to ensure that your automated jobs are executed regularly. To do this, anacron checks to find out when the job was last run, and then checks how often you told it to run the job.

Suppose you set anacron to run scripts every five days. Every time you turn on your computer or wake it from sleep, anacron scans its logs to determine if you need to run a job. If a job was run five days or more ago, anacron runs the job.

Cron job

Many Linux systems bundle some maintenance work and let cron do it. I like to keep my work separate from my systems work, so I created a directory in my home directory. Specifically, there is a hidden folder called ~/.local ("local" means it's customized for your user account, not your "global" computer system), so I created the subdirectory etc/cron.daily as cron's home directory on my system. You must also create a spool directory to track the last time a job was run.

$ mkdir -p ~/.local/etc/cron.daily ~/.var/spool/anacron

You can put any script you want to run regularly in ~/.local/etc/cron.daily. Now copy the example script into the directory and make it executable with chmod.

$ cp example ~/.local/etc/cron.daily# chmod +x ~/.local/etc/cron.daily/example

Next, set up anacron to run any scripts located in the ~/.local/etc/cron.daily directory.

anacron

By default, most of the cron system is considered the domain of system administrators because it is typically used for important low-level tasks such as rotating log files and updating certificates. The configuration demonstrated in this article is designed for the average user to set up personal automation tasks.

To configure anacron to run your cron jobs, create a configuration file in/.local/etc/anacron tab:

SHELL=/bin/shPATH=/sbin:/bin:/usr/sbin:/usr/bin1 0 cron.mine run-parts /home/tux/.local/etc/cron.daily/

This file tells anacron to run (run-parts) all executable scripts found in ~/.local/etc/cron.daily after a delay of 0 minutes every new day. Sometimes, a delay of a few minutes is used so that your computer isn't bombarded with all the possible tasks once you log in. This setting is suitable for testing.

cron.mine value is an arbitrary name for the process. I call it cron.mine, but you can call it cron.personal or penguin or whatever you want.

Verify the syntax of your anacontab file:

$ anacron -T -t ~/.local/etc/anacrontab \-S /home/tux/.var/spool/anacron

Silence means success.

Add anacron to.profile

Finally, you must make sure anacron runs in your native configuration. Because you are running anacron as a normal user, not root, you must boot it into your local configuration: an anacron tab file that tells anacron what to do, and a spool directory that helps anacron track how many days each job was last executed:

anacron -fn -t /home/tux/.local/etc/anacrontab \-S /home/tux/.var/spool/anacron

The-fn option tells anacron to ignore timestamps, which means you force it to run your cron job anyway. This is purely for testing purposes.

Test your cron assignment

Now that everything is set up, you can test your homework. Technically, you can test without restarting, but restarting makes the most sense because that's what it's designed to handle broken and irregular login sessions. Take a moment to restart your computer, log in, and look for test files:

$ ls /tmp/hello/tmp/hello

Assuming the file exists, your sample script has executed successfully. You can now remove the test option from ~/.profile and leave this as your final configuration.

anacron -t /home/tux/.local/etc/anacrontab \-S /home/tux/.var/spool/anacron

Use of anacron

You've configured your personal automation infrastructure, so you can put any script you want your computer to manage for you in ~/.local/etc/cron.daily and it will run as planned.

This depends on how often you want the job to run. The sample script is executed once a day. Obviously, it depends on whether your computer is on and awake on any given day. If you use your computer on Fridays but set it for weekends, the script won't run on Saturdays and Sundays. On Monday, however, the script will execute because anacron will know that at least one day has passed. You can add weekly, biweekly, or even monthly directories to ~/.local/etc to schedule various intervals.

To add a new interval:

Add a directory to ~/.local/etc (for example cron.weekly). Add a line to ~/.local/etc/anacrontab to run scripts in the new directory. For weekly intervals, the configuration is as follows. 7 0 cron.mine run-parts /home/tux/.local/etc/cron.weekly/(a value of 0 can be chosen for a number of minutes to appropriately delay the start of the script). Put your scripts in the cron.Weekly directory. Thank you for reading! About "how to use anacron command in linux" this article is shared here, I hope the above content can be of some help to everyone, so that everyone can learn more knowledge, if you think the article is good, you can share it to let more people see it!

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