want to su without password inside shell script

Question

I have written a script which will run a script for a backup before:

# cat backup-before-shutdown
#Scritp to take backup before shutdown
#Author Ashish Karpe

echo "Taking backup to s3"
su ubuntu /bin/sh /home/ubuntu/backup.sh
/bin/sh /home/ubuntu/backup-to-s3.sh

Normally when I switch the user from root to ubuntu it doesn't ask password as its switching from root to ubuntu but it's asking while running the script. So what should I do to avoid the password in my script?

Answer 1

If the script is running as the root user, this sudo command string should execute the command without requiring a password.

sudo -H -u ubuntu /bin/sh /home/ubuntu/backup.sh