To effectively manage and stagger automated upgrades across multiple groups of Ubuntu servers, scheduling upgrades on specific days for different server groups offers a structured and reliable method. This approach ensures that upgrades are rolled out in a controlled manner, reducing the risk of potential disruptions.

Here's an example Ansible playbook that illustrates how to set this up. It installs unattended-upgrades and configures systemd timers to manage upgrades on specific weekdays for three distinct groups of servers.

  ---
  - hosts: all
    become: yes
    vars:
      unattended_upgrade_groups:
        - name: staging_batch1
          schedule: "Mon *-*-* 02:00:00"  # Updates on Monday
        - name: staging_batch2
          schedule: "Wed *-*-* 02:00:00"  # Updates on Wednesday
        - name: staging_batch3
          schedule: "Fri *-*-* 02:00:00"  # Updates on Friday

    tasks:
      - name: Install unattended-upgrades
        apt:
          name: unattended-upgrades
          state: present

      - name: Disable automatic updates to control manually
        copy:
          dest: /etc/apt/apt.conf.d/20auto-upgrades
          content: |
            APT::Periodic::Update-Package-Lists "1";
            APT::Periodic::Download-Upgradeable-Packages "0";
            APT::Periodic::AutocleanInterval "7";
            APT::Periodic::Unattended-Upgrade "0";
          mode: '0644'

      - name: Setup systemd service and timer for each group
        loop: "{{ unattended_upgrade_groups }}"
        block:
          - name: Create systemd service for unattended-upgrades for {{ item.name }}
            copy:
              dest: "/etc/systemd/system/unattended-upgrades-{{ item.name }}.service"
              content: |
                [Unit]
                Description=Run unattended upgrades for {{ item.name }}

                [Service]
                Type=oneshot
                ExecStart=/usr/bin/unattended-upgrade
              mode: '0644'

          - name: Create systemd timer for {{ item.name }}
            copy:
              dest: "/etc/systemd/system/unattended-upgrades-{{ item.name }}.timer"
              content: |
                [Unit]
                Description=Timer for unattended upgrades on {{ item.schedule }} for {{ item.name }}

                [Timer]
                OnCalendar={{ item.schedule }}
                Persistent=true

                [Install]
                WantedBy=timers.target
              mode: '0644'

          - name: Enable the timer for {{ item.name }}
            systemd:
              name: "unattended-upgrades-{{ item.name }}.timer"
              enabled: yes

          - name: Start the timer for {{ item.name }}
            systemd:
              name: "unattended-upgrades-{{ item.name }}.timer"
              state: started

Ubuntu only does security updates, no? So that seems like a bad idea.

If you still want to do that, I guess you'd probably need to run your own package mirror, update that on Monday, and then point all the machines to use that in the sources.list and run unattended-upgrades on different days of the week.

In an ideal world, there should be 3 separated environments of the same app/service:
devel → staging → production.

Devel = playground, stagging = near identical to the production.

So you can test the updates before fixing production.

A cron job that runs when you want it to instead of the unattended updates metapackage.

Maybe you could switch to an image based distro which is easy to roll back and won't boot into a broken image.

Small number of machines?

Disable unattended-upgrades and use crontab to schedule this on the days of the week you want.

Eg, Monday each week at 4 am - every combination of dates and days is possible with crontab. 2nd Tuesdays in a month? No problem.

0 4 * * MON apt-get update && apt-get upgrade && reboot

(You can also be more subtle by calling a script that does the above, and also does things like check whether a reboot is needed first)

Dozens, hundreds or thousands of machines? Use a scheduling automation system like Uyuni. That way you can put machines into System Groups and set patching schedule like that. And you can also define groups of machines, either ad-hoc or with System Groups, to do emergency patching like that day's openssh critical vuln by sending a remote command like the above to a batch at a time.

All of that is pretty normal SME/Enterprise sysadminning, so there's some good tools. I like Uyuni, but others have their preference.

However - Crowdstrike on Linux operates much like CS on Windows - they will push out updates, and you have little or no control over when or what. They aren't unique in this - pretty much every AV needs to be able to push updates to clients when new malware is detected. But! In the example of Crowdstrike breaking EL 9.4 a few months ago when it took exception to a new kernel and refused to boot, then yes, scheduled group patching would have minimised the damage. It did so for us, but we only have CS installed on a handful of Linux machines.

Cron with the -y option on apt commands.