16.04 Xenial

APT automatic update check: enabled

APT automatic update download & install: disabled

No cron jobs listed below,

$ for user in $(cut -f1 -d: /etc/passwd); do sudo crontab -u $user -l; done

The system suddenly topped by heavy load pertaining to both CPU and Network IO from the aroused unattended-upgrade for several minutes.

Why could it happen when automatic update download & install were totally disabled?

  • 2
    A better question is why does it hammer the CPU. Disabling it is just a work-around for a bigger issue. I'm getting this on 18.04 VM this morning. Running 100% for about 10 mins when booted. Now at about 25% for last 20 mins. Reminds me of Windows updates. – bshea Sep 22 '19 at 12:12
  • @bshea Its actually worse than Windows updates. – Rolf Mar 1 at 10:02

The functionality on unattended-upgrades is automatically enabled after the installation of 16.04 Xenial Server. I mistakenly didn't really disable it so observed the unexpected behaviors above. Method Two here I had followed is unlikely effective.

To properly disable the automatic updates, we need change the configuation on /etc/apt/apt.conf.d/20auto-upgrades from:

APT::Periodic::Unattended-Upgrade "1";


APT::Periodic::Unattended-Upgrade "0"; 

If your OS uses systemd then:

sudo systemctl mask unattended-upgrade.service

would also stop it from automatically running.

The main issue I have is: why is it taking up 100% CPU for downloading some files?

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