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If it exists, what is the maximum number of cron jobs (entries?) that can be added to a server's crontab? How do I tell? I'm on RHEL 6.

I googled around, but did not see a conclusive answer -- some were 256, some 65K, some said limitless.

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Checkout this related answer on serverfault.com/questions/85341/crontab-size-limit – Anthony Hatzopoulos Jul 18 '12 at 23:38
Thank you, that was one of the pages I found in my search. – KM. Jul 19 '12 at 12:14
up vote 3 down vote accepted

To answer your question you should have a look at the cron implementation for your distribution. RHEL seems to use cronie - you can find the source code for cronie online.

cronies limit seems to depend on the filesystem (maximum file size) as the cron daemon stores the crontab entries per user in a linked list - see user.c from cronie for details. This means the maximum number of job entries for crontab is basically unlimited.

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Thank you. So, does "linked list" imply "unlimited" ... ? until all the memory is taken up ... ? – KM. Jul 19 '12 at 12:07
@KM01 not necessarily as you still can implement/enforce limits but typically yes linked list often means unlimited size. The linked source code shows no restrictions re. the number of entries. And it would take a lot of entries to fill the memory with crontab entries. – Ulrich Dangel Jul 19 '12 at 12:16

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