diff options
| author | Mark McNally <mark@mcnally.je> | 2021-06-30 18:01:49 +0100 |
|---|---|---|
| committer | Mark McNally <mark@mcnally.je> | 2021-06-30 18:01:49 +0100 |
| commit | 9af5424f70e3f84cd08bdc771304d1c200c38c6c (patch) | |
| tree | d7292a4948e66e24eb2c6901237d8673db3f8988 | |
| parent | e67d34aeadf3983a9ef908b2875ee950650ae760 (diff) | |
Added a articel on how to use cron. Added links to this article on
current articels that mention cron
| -rw-r--r-- | certbot.html | 8 | ||||
| -rw-r--r-- | cron.html | 197 | ||||
| -rw-r--r-- | maintenance.html | 2 |
3 files changed, 204 insertions, 3 deletions
diff --git a/certbot.html b/certbot.html index dded807..cabf6cd 100644 --- a/certbot.html +++ b/certbot.html @@ -97,7 +97,7 @@ ufw allow 443</code></pre> <p> Of course, you don't want to have to remember to log in to renew them every three months, so it's easy to tell the server to automatically run this command. - We will use a cronjob for this. Run the following command: + We will use a <a href="cron.html">cronjob</a> for this. Run the following command: </p> <pre><code>crontab -e</code></pre> @@ -110,7 +110,7 @@ ufw allow 443</code></pre> </aside> <p> - This <code>crontab</code> command will open up a file for editting. + This <code>crontab</code> command will open up a file for editing. A crontab is a list of commands that your operating system will run automatically at certain times. We are going to tell it to automatically try to renew our certificates every month so we never have to. </p> @@ -125,6 +125,10 @@ ufw allow 443</code></pre> Save the file and exit to activate this cronjob. </p> + <p> + For more on cron and crontabs please <a href="cron.html">click here!</a> + </p> + <span class=next><a href="html.html">Next: Use HTML to Make Simple Webpages</a></span> </main> <footer><a href="https://landchad.net">LandChad.net</a></br>Because Everyone should be an Internet LandChad.</br><li><a href="index.html"><img src="pix/chad.gif" alt="chad"></a></li><li><a href="rss.xml"><img src="pix/rss.svg" alt="RSS"></a></li><li><a href="pix/btc.png"><img src="pix/btc.svg" alt="BTC"></a></li><li><a href="pix/xmr.png"><img src="pix/xmr.svg" alt="XMR"></a></li><li><a href="https://github.com/lukesmithxyz/landchad"><img src="pix/git.svg" alt="Github"></a></footer> diff --git a/cron.html b/cron.html new file mode 100644 index 0000000..cc0ac0d --- /dev/null +++ b/cron.html @@ -0,0 +1,197 @@ +<!DOCTYPE html> +<html lang=en> + <head> + <title>Cronjobs</title> + <meta charset="utf-8"/> + <link rel="shortcut icon" href="favicon.ico" type="image/x-icon" /> + <link rel='stylesheet' type='text/css' href='style.css'> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <link rel='alternate' type='application/rss+xml' title='Land Chad RSS' href='/rss.xml'> + </head> +<body> + <header><h1>Using Cronjobs to run scheduled tasks</h1></header> + <nav></nav> + <main> + <p> + Cron is a service that lets you run scheduled tasks. These tasks are called <strong> cronjobs. </strong> If you have already followed the initial course you will have already used cron when you set up certbot. + </p> + <h2> What tasks would I want to schedule? </h2> + <p> + You can schedule anything! Some examples of what you might have done already include: + <ul> + <li> <code> updatedb </code> to update your <code> locate </code> database </li> + <li> <code> certbot </code> to update renewing of your https certs </li> + </ul> + Some tasks that you might <em>want</em> to schedule may include: + <ul> + <li> Package updates - if you really just want to leave your server alone you can automated updating packages on your server </li> + <li> Backups - you may want to backup certain files every day and some every week, this is possible with cron </li> + </ul> + <p> + And many more, anything you can do can be turned into a cronjob. + </p> + + <h2> How do I schedule things? </h2> + + <p> + You can schedule tasks in the following ways: + <ol> + <li> Your users crontab </li> + <li> System wide cron directories </li> + </ol> + + + + <h3> Your user crontab </h3> + + <p> + This the preferred method for personal tasks and scripts, it's also the easiest to get started with. Run the command <code> crontab -e </code> to access your users crontab + </p> + <aside> + <p> + These crontabs are located at <code> /var/spool/cron/crontabs/ </code> If you wanted to you can edit these files instead of running <code> crontab -e </code> + </p> + </aside> + + <p> + Once you have figured out the command you want to run you need to figure out how often you want to run it and when. I am going to schedule my system updates once a week on at 3:30 AM on a Monday. + </p> + <p> + We now have to convert this time (Every Monday at 3:30 AM) into a cron time. Cron uses a simple but effective way of scheduling when to run things. + </p> + <p> + Crontab expressions look like this <code> * * * * * command-to-run </code> + <pre> + .---------------- minute (0 - 59) + | .------------- hour (0 - 23) + | | .---------- day of month (1 - 31) + | | | .------- month (1 - 12 + | | | | .---- day of week (0 - 6) + | | | | | + * * * * * + </pre> + <br> + <aside> + <p> Run the command <code> cat /etc/crontab </code> to see something similar to the above </p> + </aside> + + <p> + So for our Monday at 3:30AM job we would do the following: + <pre> + <code> 30 3 * * 1 apt-get -y update && apt-get -y dist-upgrade </code> + </pre> + <br> + <aside class=callout> + <p> + For day of the week field (the last field), the week starts on a Sunday, so Monday is <code> 1 </code> + </p> + </aside> + <br> + <aside> + <p> + The website <a href="crontab.guru">https://crontab.guru</a> is insanely helpful for figuring out specific cron timings + </p> + </aside> + <p> + Lets add another Job, our backup job (for the purposes of this our backup command is just called <code> backup </code> We want to run <code> backup </code> Every evening at 11PM, once we work out the timings for this we can add the to the same file as the above by running <code> crontab -e </code> This would mean our full crontab would look like this: + <pre> + <code> 30 3 * * 1 apt-get -y update && apt-get -y dist-upgrade </code> + <code> 0 23 * * * backup </code> + </pre> + + <h3> System wide cron directories </h3> + + <p> + Run the command <code> ls /etc/cron* </code> you should see a list of directories and there contents. The directories should be something like the below + <ul> + <li> /etc/cron.d <em> This is a crontab like the ones that you create with </em> <code> crontab -e </code> </li> + <li> /etc/cron.hourly </li> + <li> /etc/cron.daily </li> + <li> /etc/cron.weekly </li> + <li> /etc/cron.monthly </li> + </ul> + + <p> + + The directories cron.{hourly,daily,weekly,monthly} are where you can put <strong> scripts </strong> to run at those times. You don't put normal cron entries here. I prefer to use these directories for system wide jobs that don't relate to an individual user. For example If we wanted to put our backup job in <code> /etc/cron.daily </code> we would do the following: + <ol> + <li> Create and edit the file <code> /etc/cron.daily/backup/ </code>: + <ul> + <li> <code> vim /etc/cron.daily/backup </code> </li> + </ul> + <li> Add the backup command in there, we can also add some logging because it's a full script. The full thing will look like this: </li> + <p> + <pre> + #!/bin/sh + + # the logger command generates system logs + logger "starting backup daily job" + + # backup is hypothetical backup command + backup + + logger "finished backing up" + </pre> + </p> + </li> + <li> Save that file </li> + <li> Make that executable: </li> + <ul> + <li> <code> chmod +x /etc/cron.daily/backup </code> </li> + </ul> + </ol> + + <p> + It's that easy, no messing around with cron timers! A downside of this is that you can't choose when these run, most of the time they will run at ~6:30am every hour,day,week,month. + </p> + + <p> + That's it! There is not much more to know about cron. Hopefully you now know the appropriate cron method and have the ability to correctly schedule your tasks. + </p> + + <h2> Contribution </h2> + + <p> + This article was written by Mark McNally + </p> + + <ul> + <li> + I am a (internet) LandChad, my website is <a href="https://mark.mcnally.je">here</a> + </li> + <li> + Contact me about this article or just because <a href="mailto:mark@mcnally.je">here</a> + </li> + <li> + I have a <a href="https://www.youtube.com/channel/UCMiInY8BhSUtCarO6uu6i_g">youtube channel</a> where I may post some LandChad related content as well as other content that you will hopefully find interesting + <li> If you feel like donating: </li> + <ul> + <li> XMR: <code> 42ueuWXJGP48xtahfnujWDMFHJVdMGeFj85jxuwPBygkVw1GEBbHfTsDFBByTSLXpDV4bKcNr7EPCfvSJpyYLY5HPvqUmRB </code> </li> + <li> BTC: <code> 36mXUtU6Kh9pmYvGYPLY7peHU4TR7FBATT </code> </li> + </ul> + </ul> + <p> + Yes I know I need to set up OpenAlias... + </p> + + + + + + + + + + + </main> + <footer><a href="https://landchad.net">LandChad.net</a></br>Because Everyone should be an Internet LandChad.</br><li><a href="index.html"><img src="pix/chad.gif" alt="chad"></a></li><li><a href="rss.xml"><img src="pix/rss.svg" alt="RSS"></a></li><li><a href="pix/btc.png"><img src="pix/btc.svg" alt="BTC"></a></li><li><a href="pix/xmr.png"><img src="pix/xmr.svg" alt="XMR"></a></li><li><a href="https://github.com/lukesmithxyz/landchad"><img src="pix/git.svg" alt="Github"></a></footer> +</body> +</html> + + + + + + + + diff --git a/maintenance.html b/maintenance.html index 5cdbb1a..264fe68 100644 --- a/maintenance.html +++ b/maintenance.html @@ -113,7 +113,7 @@ nginx: /usr/sbin/nginx /usr/lib/nginx /etc/nginx /usr/share/nginx /usr/share/man /usr/share/nginx/modules-available/mod-stream.conf</code></pre> <p> - <code>updatedb</code> is an ideal candidate for a cronjob so you don't have to worry about running each time. + <code>updatedb</code> is an ideal candidate for a <a href="cron.html">cronjob</a> so you don't have to worry about running each time. For example, adding the following to your crontab will run <code>updatedb</code> every 30 minutes: </p> <pre><code>*/30 * * * * /usr/bin/updatedb</code></pre> |