[SOLVED] Tar archiving via cron does not work

taru.tarak · 04-13-2017, 04:38 AM

Hello,

I am facing an issue with tar archiving, the execution of tar in the command line works fine without problems:

tar -czf /backup/test/bkp_`date +%d%b%Y_%H%M%S`.tar.gz -P /var/www/html/tarak

However, when I schedule the command for a daily backup (let's say at 13.15) in crontab -e, it is not executing, i.e. the backup does not update using the following command:

15 13 * * * tar -czf /backup/test/bkp_`date +%d%b%Y_%H%M%S`.tar.gz -P /var/www/html/tarak
=======================

CentOS Version: 6.8 (Final)

Is there a way how I can get this running? What is the recommended ?

Any suggestion would be appreciated.

Regards,
Tarak Nath

r3sistance · 04-13-2017, 04:42 AM

Is cron finding tar, that'd be my first question, when it comes to cron jobs, I always make sure to use absolute links to programs since cron does not invoke /etc/bashrc and so will not have the same settings for PATH

To confirm where tar is.

Code:

# which tar
/bin/tar

A quick example of how PATH can differ

Code:

# echo $PATH
/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
# crontab -l
* * * * * echo $PATH > /root/cronpath
# cat /root/cronpath
/usr/bin:/bin

Turbocapitalist · 04-13-2017, 05:00 AM

Yes, and look for path to date as well. But here the problem is most likely the unescaped percent signs.

Code:

tar -czf /backup/test/bkp_$(date +\%d\%b\%Y_\%H\%M\%S).tar.gz -P /var/www/html/tarak

See the crontab manual page for the details.

Code:

man 5 crontab

taru.tarak · 04-13-2017, 05:02 AM

Thank you for the quick reply.
I have checked the tar path and its /bin/tar
Now I have modified the cronjob as below:

18 15 * * * /bin/tar -czf /backup/test/bkp_`date +%d%b%Y_%H%M%S`.tar.gz -P /var/www/html/tarak

But it's still not executing.

michaelk · 04-13-2017, 05:06 AM

Welcome to LinuxQuestions.

cron uses % as a special character and needs to be escaped.

Code:

15 13 * * * tar -czf /backup/test/bkp_`date +\%d\%b\%Y_%H\%M\%S`.tar.gz -P /var/www/html/tarak

Due to how sorting works I always suggest file naming using Year first.

Too late...

taru.tarak · 04-13-2017, 06:03 AM

Thank you very much. I have again modified the cron as below:

25 16 * * * /bin/tar -czf /backup/test/bkp_`date +"\%Y\%b\%d_\%H\%M\%S"`.tar.gz -P /var/www/html/tarak

And its executing perfectly without any problem. What a quick solution !

Habitual · 04-13-2017, 06:31 AM

echo is a good tool for this type of debugging, IMO.
That and the cron's mail service.

Code:

echo $(which tar) -czf /backup/test/bkp_$(date +"%d%b%Y_%H%M%S").tar.gz -P /var/www/html/tarak

I removed the will-be-deprecated back ticks in favor of new styple $(sub_shell). This keeps me and my
quotes nice and happy.

Just sayin'

taru.tarak · 04-13-2017, 09:19 AM

Thank you again !