Ubuntu 18.04 の tomcat8 を ユーザ指定して実行する [Run tomcat 8 of Ubuntu 18.04 as specific user]

www として実行する。
run as www user.

sudo vi /etc/default/tomcat8

# Run Tomcat as this user ID. Not setting this or leaving it blank will use the
# default of tomcat8.
TOMCAT8_USER=www

# Run Tomcat as this group ID. Not setting this or leaving it blank will use
# the default of tomcat8.
TOMCAT8_GROUP=www

# change log dir's owner
sudo chown www.adm /var/log/tomcat8
# clean up log dir
sudo rm /var/log/tomcat8/*

# change conf dir's owner
cd /etc/tomcat8
sudo chown -R root.www ./*

# change work dir's owner
cd /var/cache
sudo chown -R www.www tomcat8

# clean up tmp dir
sudo rm -r /tmp/tomcat8-tomcat8-tmp

sudo vi /etc/init.d/tomcat8

TOMCAT8_USER=www
TOMCAT8_GROUP=www