Seems like a duplicate of: How to disable release upgrade notification emails?
While this is for 14.04 the general guideline should hold still, in particular - stopping that one job in cron
.
Top answer:
By default cron
sends mail to the email address mentioned in the MAILTO
environment variable on crontab
, presumably you have set the email address, so any STDOUT/STDERR from any cron
job will be sent to the email address.
The output is from /usr/lib/ubuntu-release-upgrader/release-upgrade-motd
script (run by the weekly job /etc/cron.weekly/update-notifier-common
) that checks for a new version, and dump the content of /var/lib/ubuntu-release-upgrader/release-upgrade-available file.
You have a few options:
Disable the job
Redirect STDOUT/STDERR
from the script to /dev/null
Set MAILTO=""
so that no mail will be sent. As /usr/sbin/anacron
exists the script will be run by anacron, so setting this in /etc/anacrontab
would do too.