we experience difficulties with crond behaviour sending mail since CentOS 8.1. The cron job is the same like we used in CentOS 7.
Meanwhile we found the reason for the bug - actually we do not know if it is related to a specific version of CentOS or a specific kind of command as cron job.
Let me explain what we have:
- sssd for ssh login of ldap user - crond for cron jobs :)
If we stop sssd and restart crond cron starts to send mails again!
We started with sssd on newly provisioned machines with CentOS 8. We do not know if this is the same on CentOS 7.
We send mails only to root. So no remote user is involved in cron.
From our perspective it is a bug. How could we dive deeper to find the specific reason?
What do you think about this?
Tobias
On 21 Mar 2020, at 11:56, Tobias Kirchhofer wrote:
On 27 Feb 2020, at 14:42, Jonathan Billings wrote:
On Feb 27, 2020, at 08:01, Tobias Kirchhofer collect@shift.agency wrote:
Hi,
we experience difficulties with crond behaviour sending mail since CentOS 8.1. The cron job is the same like we used in CentOS 7.
crontab -l /usr/bin/python3 -c 'import random; import time; time.sleep(random.random() * 3600)' && /usr/local/bin/backup.sh
Is this literally what your crontab looks like? Because that’s not valid crontab syntax.
This is what it is literally:
0 5 * * * /usr/bin/python3 -c 'import random; import time; time.sleep(random.random() * 3600)' && /usr/local/bin/backup.sh
backup.sh writes the backup to the remote backup server. There are around 30 machines with the same cron job. The python part spreads the jobs over an hour so that the backup server is not struck at once from about 30 machines.
The change in behaviour is that crond sends no mail anymore. It is because of the logical and (&&). Without this crond sends mails.
What has changed in CentOS 8 and does anyone has an idea how we could fix it?
There aren’t any significant changes in ‘cronie’ in 8.1, looking at the spec file.
Assuming the crontab you wrote above included the time spec too, I’d check to make sure the first command isn’t exiting with a non-zero exit code.
The command chain is running propery, STDOUT output is visible in system log (excerpt from logwatch email):
--------------------- Cron Begin ------------------------ **Unmatched Entries** CMDOUT (### Starting backup. Host: host.example.com Backupserver: 10.9.1.5 Path: /borgbackup/vm/host-example-com Date: Fri Mar 20 05:13:46 CET 2020 ###) CMDOUT (Creating archive at "borg@IP:/borgbackup/vm/host-example-com::{now:%Y-%m-%d_%H:%M}") …Its just not sending an email.
What is additionally irritating is that it is only on a few machines. All machines are identically provisioned with ansible.
The situation is not mission critical but it should work. Strange.
Tobias