➥ Where is the cron / crontab log? / Enable Cron Log in Ubuntu 16.04

1. modify rsyslog config: open /etc/rsyslog.d/50-default.conf,remove # before cron.*
pico /etc/rsyslog.d/50-default.conf

# Default rules for rsyslog.
# For more information see rsyslog.conf(5) and /etc/rsyslog.conf

# First some standard log files. Log by facility.
auth,authpriv.* /var/log/auth.log
*.*;auth,authpriv.none -/var/log/syslog
cron.* /var/log/cron.log
#daemon.* -/var/log/daemon.log
kern.* -/var/log/kern.log
#lpr.* -/var/log/lpr.log
mail.* -/var/log/mail.log
#user.* -/var/log/user.log

2. chown syslog:admin cron.log
3. restart rsyslog service: sudo service rsyslog restart
sudo service rsyslog restart

4. restart cron service: service cron restart
service cron restart

Now you can check cron log from file cat /var/log/cron.log
if you have problems please reboot the server!