Simple docker cron sidecar container based on alpine image

cronscript.sh

#!/usr/bin/env sh
echo "Job started: $(date)"
# Add additional instructions
echo "Job finished: $(date)"

Dockerfile

FROM alpine:3.8

# Alpine comes with built in cron schedules
# min   hour    day     month   weekday command
# */15    *       *       *       *       run-parts /etc/periodic/15min
# 0       *       *       *       *       run-parts /etc/periodic/hourly
# 0       2       *       *       *       run-parts /etc/periodic/daily
# 0       3       *       *       6       run-parts /etc/periodic/weekly
# 0       5       1       *       *       run-parts /etc/periodic/monthly

# Place script in appropriate folder
COPY cronscript.sh /etc/periodic/15min/backup

# bash-4.4# crond --help
# BusyBox v1.28.4 (2018-05-30 10:45:57 UTC) multi-call binary.
# Usage: crond -fbS -l N -d N -L LOGFILE -c DIR
#        -f      Foreground
#        -b      Background (default)
#        -S      Log to syslog (default)
#        -l N    Set log level. Most verbose 0, default 8
#        -d N    Set log level, log to stderr
#        -L FILE Log to FILE
#        -c DIR  Cron dir. Default:/var/spool/cron/crontabs 

# This runs cron in the foreground with loglevel 2
CMD [ "crond", "-l", "2", "-f" ]

How can we start the crond with non root user ?