When provisioning a new machine in Google Compute Engine with Vagrant, I spotted the following error messages when updating the system:

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Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable)
E: Unable to lock directory /var/lib/apt/lists/

It appears to be that I was just behind on the race to grab the lock on the APT update. Without getting the latest index, I am not able to upgrade the packages. An simple solution is to wait it out:

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#!/usr/bin/env bash
#
# System Update
# =============
apt-get update
while [ "$?" != "0" ]; do
  sleep 5
  apt-get update
done
apt-get -y dist-upgrade

This is for Debian/Ubuntu flavored systems.

Keep a single server up to date is easy, but updating multiple servers at once, you need tools like Ansible. For each server, here is a list of basic steps:

1. Check if there are packages available to be upgraded
2. Upgrade all packages to the latest version
3. Check if a reboot is required
4. Reboot the server

When we log into the remote server, we might see the message showing the number of packages can be updated. The message is generated by:

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$ sudo /usr/lib/update-notifier/update-motd-updates-available 
25 packages can be updated.
18 updates are security updates.

And it is available at:

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$ cat /var/lib/update-notifier/updates-available                                       
25 packages can be updated.
18 updates are security updates.

We don’t need that detailed information, we just simply want to know if there are update available.

Shell script /usr/lib/update-notifier/apt-check shows any pending updates:

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$ /usr/lib/update-notifier/apt-check
25;18

To list all the packages instead of simple packages;security format:

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$ /usr/lib/update-notifier/apt-check --package-names

--package-names option will write data to stderr instead of stdout. If there are no packages needed to be installed, then the stderr should be empty.

If there are packages to be installed or upgraded. Ansible has the apt module to manage them in Debian/Ubuntu based systems.

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- name: Check if there are packages available to be installed/upgraded
  command: /usr/lib/update-notifier/apt-check --package-names
  register: packages
- name: Upgrade all packages to the latest version
  apt: update_cache=yes upgrade=dist
  when: packages.stderr != ""