Cronjob can not execute smartctl?

Question

I have a cronjob installed (Ubuntu 16) that runs with the root user. So in

sudo crontab -e

I have the following entry:

10 5 * * mon /home/userA/raidchecker.sh

And the script raidchecker.sh does this:

#!/bin/sh
mail=`which mail`
rec="[email protected] [email protected]"
now=$( date +%Y%m%d-%H%M-%S )
mdstat=$( cat /proc/mdstat )
details=$( /sbin/mdadm --detail /dev/md2 )
diskusg=$( df -kh )
disk1=$( smartctl -A /dev/sda | grep Realloc | grep Sector )
disk2=$( smartctl -A /dev/sdb | grep Realloc | grep Sector )
disk1f=$( smartctl -A /dev/sda )
disk2f=$( smartctl -A /dev/sdb )
buddyinfo=$( cat /proc/buddyinfo | grep Normal )

echo "Check from $now\n\n=================\nMemory Fragmentation:\n$buddyinfo\n\nAll partitions:\n\n$mdstat\n\n=================\nData Partition:\n\n$details\n\n=================\nDisk Usage:\n$diskusg\n\n=================\nSMARTCTL:\n\nData Disk /dev/sda and sdb:\n$disk1\n$disk2\n\nFull Reports:\nDisk1:\n$disk1f\n\nDisk2:\n$disk2f" | $mail -s "Check from $now" $rec

When I execute the script manually from the shell ./raidchecker.sh the email contains all infos as expected.

When the cronjob executes the script, the parameters disk1, disk2, disk1f and disk2f are empty (do not contain any data).

Why?

Answer 1

The solution was to use /usr/sbin/smartctl instead of smartctl in the script, only this way the cronjob could execute this command.

Answer 2

Using a crontab, most of the usual environment set for a regular user login is absent or reduced (unless you set it), when the script is run automatically by cron.

To be sure, it's better to either provide a relevant PATH, or give the absolute path to all commands.

Always test a crontab (setting a time a couple minutes after the current time).

• If you want to receive (by email) the standard and also error output, only add 2>&1 to the command in the crontab
• If you do not want to receive any of the output of the crontab command (by email), add > /dev/null 2>&1