Why is it bad directly editing /var/spool/cron/root ?

rdan · Sep 16, 2019

eva2000 said: ↑

Did you try editing /var/spool/cron/root directly ? that's a big no no, crontab -e is correct way to edit cronjobs for root user.
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As you mention on the other thread, but I always do this when adding my rsync cron with very long arguments/options.

eva2000 · Sep 16, 2019

Biggest issue is you can end up deleting or wiping your /var/spool/cron/root file by accident if manual editing is done incorrectly !

crontab -e has syntax error checking while editing file manually wouldn't also see https://serverfault.com/a/347321/34814 and https://ubuntuforums.org/showthread.php?t=2173811

If you modify the user file under crontabs, it should work. However, there are two issues to take into consideration:

If you mistyped the cron entry in the file, you will not be warned as opposed to using crontab -e command.

You can not edit your user file under crontabs directly without login as root or using sudo. You will get permission denied error.

Edit

One more point to add. When you edit the file directly, you may be warned by the text editor if you opened the file twice (two users accessing the same file). However, the cron list will be overwritten when using crontab -e from two different shell sessions of the same user. This is another difference.
Click to expand...

manual edits can also get overwritten by crontab -e edit activity too

The /var/spool/cron files are created as cron tables are edited. It even says in the files to not edit--because they can get overwritten automatically by any cron edit activity. So it is generally bad form to edit an auto-generated file because you can never be sure when it will get changed. These files are controlled by the system. Why can't you put the script that you want to run in root's crontab (/etc/crontab)?

The purpose for this convoluted method of running cronjobs is so that the jobs will always get executed and there will never be a file lock collision if the crontab gets edited at the same time it is supposed to execute. It helps to guarantee the execution of scheduled jobs. Editing the spool though does not guarantee execution.
Click to expand...

proper way to edit or insert cronjobs is either crontab -e or use cronjob -l to list cronjobs piped into a text file and then edit that text file and then use crontab text file to re-register and reimport the edited list of cronjobs via crontab command
Code (Text):
# save all cronjobs by root user into listofcronjobs.txt text file (serves as backup too)
crontab -l > listofcronjobs.txt
# then edit listofcronjobs.txt
# then reload edited listofcronjobs.txt
crontab listofcronjobs.txt
That is how centmin mod's automated routines add cronjobs

rdan · Sep 16, 2019

Thanks for the new lesson Eva .

rdan · Sep 16, 2019

eva2000 said: ↑

use cronjob -l to list cronjobs piped into a text file and then edit that text file and then use crontab text file to re-register and reimport the edited list of cronjobs via crontab command
Click to expand...

That is a very nice steps Eva.
I'll take note this for my upcoming servers.

jacknguyen · Mar 21, 2023

I found the easy way to edit the cronjobs for newbie like me.
Code:
crontab -l > listcron
echo "* * * * * /cron.../.... " >> listcron
then
crontab listcron

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