root crontab not executing

Question

I'm setting up my Debian server to backup my databases with crontab, the mysqldump utility and gunzip.

For some reason, my crontab lines appear to fail, especially the crucial one:

15 2 * * * /usr/bin/mysqldump --user=root --password=XXX --all-databases | /bin/gzip > /backup/database_`date '+%d-%m-%Y'`.sql.gz

I've read several sujects about the possible origins of this behavior, but still I fail to see the reason why this crontab job still fails to create the file after I:

• Used the root privileges: I use sudo crontab -e to edit the root crontab.
• Used a whereis to find the complete paths of the commands I'm using, replacing for instance mysqldump with /usr/bin/mysqldump.
• Checked that the whole line works under root: it does create an archive with today's date, filled with the mysqldump result (showing a warning because I'm using a password in the CLI, but I don't think that'd cause any problem with crontab, right?)

I suppose something is wrong in the way I configure this line in the crontab, but I cannot see it.

Apparently, the crontab is working properly because when I append the line * * * * * env > /backup/env.txt I do get a file that contains the env content in the /backup folder...

Would someone have a clue about this?

Thank you !

~Stéphane

Answer 1

The default path for cron is:

PATH=/usr/bin:/usr/sbin:.

The date utility is located in /bin/ so you would need to either:

1. explicitly add this directory to the PATH for cron

   PATH=/bin/:/usr/bin:/usr/sbin:.
   15 2 * * * mysqldump --user=root --password=XXX --all-databases | gzip > /backup/database_$(date '+%d-%m-%Y').sql.gz
   

or

2. provide the full path for the date command:

   15 2 * * * /usr/bin/mysqldump --user=root --password=XXX --all-databases | /bin/gzip > /backup/database_$(/bin/date '+%d-%m-%Y').sql.gz
   

I prefer the first option as the second method makes it too easy to make a mistake and forget to provide the full path for all commands (such as date in your question).

Answer 2

OK, I found what was not working for me:

By tail'ing the /var/log/syslog, I discovered that crontab has a line size limit! So, when reading the line, it was stopping there: ... $(date +' making the line "bug" at execution.

My solution was to move the job to a /root/backup.sh script and to edit the crontab using:

15 2 * * * /root/backup.sh

At least, now I can backup my data!!

I hope this solution will help others ;)