Why my cronjob setup by Ansible is not running?

Question

I've setup a cron job by Ansible but when I use crontab -l it's said that my cron is empty.

Here's my script to set it up.

  - name: Setup cron to run backup.sh every midnight
    cron: 
      name="Backup S3 to GS" 
      minute="0"
      hour="0"
      job="sh ~/backup.sh"
      cron_file=backup_s3
      user=vagrant

But when I go inside the vagrant machine and ls /etc/cron.d/ I can see that backup_s3 file is there. But when I use command crontab -l it's said it's empty.

This is the content of backup_s3

#Ansible: Backup S3 to GS
0 0 * * * vagrant sh ~/backup.sh

I know that it's not running because I don't get any email saying that the backup is done and when I run the script manually it's working fine.

Answer 1

Okay. There are several layers of confusion here.

First, the crontab you see when you edit (crontab -e) or view (crontab -l) is a user cron. This sits in a magic spool directory/file. You can't edit it directly (approximately speaking), and it's not a good place to put any serious crons.

Since you are using cron_file=, Ansible is doing the appropriate thing by placing an entry in /etc/cron.d/. That means individual files can be placed there, which is much more sane than trying to edit a document. (look at all the people struggling with lineinfile here on stackoverflow)

This is why it isn't showing up in crontab -l, and it's a good thing.

As far as output from cron is concerned, does email even work for your Vagrant system? It likely doesn't. There are good ways around this. First, look at /var/log/cron. If you don't have one, look for CRON entries in /var/log/syslog. They may indicate if there are problems.

Next, crons typically don't have good access to a user shell. That means you should avoid ~. Further, if your permissions are wrong on backup.sh, it may not get executed. Finally, you can pipe output so you can see it. Here's what I'd recommend doing with your cron entry:

job="/bin/sh /home/vagrant/backup.sh >> /home/vagrant/backup.log"

You can also modify the minute/hour so it runs more frequently- so you don't have to wait overnight to see what is happening.

Once you've done that, you have plenty of places to look for information. There are two places in /var/log, there's a new backup.log which will give you information (if it exists, the cron has been run; if there is data in it, you should be able to figure out any problems).

TLDR

Change the job line. Look for execution in /var/log and /home/vagrant/backup.log.