Howto update Debian

apt-get update && apt-get upgrade
apt-get dist-upgrade
apt-get autoremove && apt-get clean
apt-get install qemu-guest-agent
ddsize=$(( $(df -m / | tail -n 1 | awk '{print $4}')-100 )) && dd if=/dev/zero of=/tmpdelme.blob bs=1M count=$ddsize && rm /tmpdelme.blob && cat /etc/debian_version
cat /etc/passwd | grep <username>
find / -user <username> 2>/dev/null && find / -group <groupname> 2>/dev/null 
usermod -u 2000 <username>
groupmod -g 2000 <groupname>
find / -user 1000 -exec chown -h 2000 {} \;
find / -group 1000 -exec chgrp -h 2000 {} \;
usermod -g 2000 <username>