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Diffstat (limited to 'cron.html')
| -rw-r--r-- | cron.html | 44 |
1 files changed, 22 insertions, 22 deletions
@@ -19,13 +19,13 @@ <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> + <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> + <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. @@ -34,25 +34,25 @@ <h2>Basic Cronjobs</h2> <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 + 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 user's crontab </p> <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. + 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 Mondays. </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> + Crontab expressions look like this <code>* * * * * command-to-run</code> The five elements before the command tell when the command is supposed to be run automatically. <p> So for our Monday at 3:30AM job we would do the following: <p> - <pre><code> .---------------- minute (0 - 59) + <pre><code>.---------------- minute (0 - 59) | .------------- hour (0 - 23) | | .---------- day of month (1 - 31) - | | | .------- month (1 - 12 + | | | .------- month (1 - 12) | | | | .---- day of week (0 - 6) | | | | | * * * * * @@ -67,7 +67,9 @@ <h3>More examples</h3> <p> - Let's 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: + Let's 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>0 23 * * * backup</code></pre> <h3>Consecutive times</h3> @@ -87,21 +89,18 @@ <p> We can also randomly specify non-consecutive arguments with a comma. Suppose you have a script you want to run at the midday of the 1st, 15th, and 20th day of every month. - You can specify that my putting <code>1,15,20</code> for the day of the month argument: + You can specify that by putting <code>1,15,20</code> for the day of the month argument: </p> <pre><code>0 12 1,15,20 * * /usr/bin/pay_bills_script</code></pre> <h3>"Every X minutes/days/months"</h3> - <p>We can also easily run a command very several minutes or months, without specifying the specific times: - </p> + <p>We can also easily run a command every several minutes or months, without specifying the specific times:</p> <pre><code>*/15 * * * * updatedb</code></pre> - <p> - This cronjob will run the <code>updatedb</code> command every 15 minutes. - </p> + <p>This cronjob will run the <code>updatedb</code> command every 15 minutes.</p> <h3>Beware of this Rookie Mistake Though...</h3> @@ -146,13 +145,14 @@ </p> <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 + 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: + </p> <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> + <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> |