Ubuntu sudden reboot

Внезапная и неожиданная перезагрузка Ubuntu

Может быть виноват unattended-upgrades

dpkg-reconfigure unattended-upgrades

nano /etc/apt/apt.conf.d/20auto-upgrades

APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";
APT::Periodic::Update-Package-Lists "0";
APT::Periodic::Unattended-Upgrade "0";

Или вообще снести его

sudo apt-get -y remove unattended-upgrades 
sudo systemctl stop apt-daily.timer 
sudo systemctl disable apt-daily.timer 
sudo systemctl stop apt-daily-upgrade.timer
sudo systemctl disable apt-daily-upgrade.timer
sudo systemctl disable apt-daily.service 
sudo systemctl daemon-reload