apt update && apt upgrade && apt dist-upgrade && apt --purge autoremove
apt full-upgrade

sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list
#sed -i 's/non-free/non-free non-free-firmware/g' /etc/apt/sources.list

apt update
apt autoremove
apt clean
apt upgrade
apt dist-upgrade
apt full-upgrade
apt autoremove

#apt install nvidia-driver firmware-misc-nonfree

reboot

$ cat /etc/debian_version
12.1

apt update && apt upgrade
#apt dist-upgrade
apt full-upgrade

sed -i 's/buster/bullseye/g' /etc/apt/sources.list
sed -i 's/bullseye\/updates/bullseye-security/g' /etc/apt/sources.list

apt update
apt upgrade
apt dist-upgrade

reboot

$ cat /etc/debian_version
11.2

apt-get update && apt-get upgrade
#apt-get dist-upgrade
apt-get full-upgrade

sed -i 's/stretch/buster/g' /etc/apt/sources.list

apt-get update
apt-get upgrade
apt-get dist-upgrade

#Restart services during package upgrades without asking? Yes.

reboot

$ cat /etc/debian_version
10.1

touch /etc/rc.local
vi /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

exit 0

vi /etc/systemd/system/rc-local.service

[Unit]
Description=/etc/rc.local Compatibility
ConditionPathExists=/etc/rc.local

[Service]
Type=forking
ExecStart=/etc/rc.local start
TimeoutSec=0
StandardOutput=tty
RemainAfterExit=yes
SysVStartPriority=99

[Install]
WantedBy=multi-user.target

chmod +x /etc/rc.local

systemctl enable rc-local

systemctl start rc-local.service

# Изменение настроек разрешения подключений пользователя root по tcp/ip
(меняем plugin с 'unix_socket' на '')

root@www:~# mysql -uroot -p mysql

Enter password:
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 2289137
Server version: 10.1.26-MariaDB-0+deb9u1 Debian 9.1

Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [mysql]> update user set plugin='' where user='root';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

MariaDB [mysql]> flush privileges;
Query OK, 0 rows affected (0.00 sec)

MariaDB [mysql]> exit
Bye

root@www:~# apt-get install -t back...

apt-get update && apt-get upgrade
apt-get dist-upgrade

sed -i 's/jessie/stretch/g' /etc/apt/sources.list

apt-get update
apt-get upgrade
apt-get dist-upgrade

# Restart services during package upgrades without asking

reboot

$ cat /etc/debian_version
9.1

nano /etc/network/interfaces
reboot