Perhaps useful for others because this question was asked a long time ago.
In your configuration file add the following lines:
# Logging
log_handler = werkzeug:WARNING, :INFO
log_level = info
logfile = /var/log/odoo/odoo.log
logrotate = True
(Change settings as you seem fit. The following URL provides a list of command line parameters which can be used in the configuration file as well: https://odoo-development.readthedocs.io/en/latest/admin/log-handler.html)
It's important that the user under which odoo runs has write permissions to the directory where the log files are stored. In my case it runs as user odoo16 member of group odoo16. So using sudo or as root create a log directory for odoo as follows:
# mkdir /var/log/odoo
# chown root:odoo16 /var/log/odoo
# chmod 775 /var/log/odoo
# ls -l /var/log
drwxrwxr-x 2 root odoo16 4096 Oct 28 16:54 odoo
The result should be as above. Next restart your odoo service, odoo16 in my case.
# systemctl restart odoo16
Why Odoo Config file: http://learnopenerp.blogspot.com/2019/10/odoo-configuration-file.html