Again ... I have never regretted taking the time to do backups AND test with a clone - however long cloning takes!
The cloning can be made while production site is being used ... at least the archive of code directory and moodledata. Unless moodledata is TB range ... and if it is, then rsync it! There would be a pause in DB when you do a DB dump - the dump would take the longest.
"No I understand the "sodium" part. Is that a extension for Moodle?"
Sodium is a PHP extension - doesn't come with Moodle code.
https://moodledev.io/general/releases/4.1
says
Server requirements
These are just the minimum supported versions. We recommend keeping all of your software and operating systems up-to-date.
* PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x and 8.1.x are supported too. See PHP for details.
** PHP extension sodium is recommended. It will be required in Moodle 4.2. For further details, see Environment - PHP extension sodium.
* PHP extension exif is recommended.
* PHP setting max_input_vars is recommended to be >= 5000 for PHP 7.x installations. It's a requirement for PHP 8.x installations. For further details, see Environment - max input vars.
Your destination version 4.2
https://moodledev.io/general/releases/4.2
Server requirements
These are just the minimum supported versions. We recommend keeping all of your software and operating systems up-to-date.
* PHP version: minimum PHP 8.0.0 Note: minimum PHP version has increased since Moodle 4.1. * PHP 8.1.x is supported too. See PHP for details.
** PHP extension sodium is required. See Environment - PHP extension sodium.
* PHP extension exif is recommended.
* PHP setting max_input_vars must be >= 5000. For further details, see Environment - max input vars.
* PHP variants: Only 64-bit versions of PHP are supported. Note: Changed since 4.1.
says
Server requirements
These are just the minimum supported versions. We recommend keeping all of your software and operating systems up-to-date.
* PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x and 8.1.x are supported too. See PHP for details.
** PHP extension sodium is recommended. It will be required in Moodle 4.2. For further details, see Environment - PHP extension sodium.
* PHP extension exif is recommended.
* PHP setting max_input_vars is recommended to be >= 5000 for PHP 7.x installations. It's a requirement for PHP 8.x installations. For further details, see Environment - max input vars.
Your destination version 4.2
https://moodledev.io/general/releases/4.2
Server requirements
These are just the minimum supported versions. We recommend keeping all of your software and operating systems up-to-date.
* PHP version: minimum PHP 8.0.0 Note: minimum PHP version has increased since Moodle 4.1. * PHP 8.1.x is supported too. See PHP for details.
** PHP extension sodium is required. See Environment - PHP extension sodium.
* PHP extension exif is recommended.
* PHP setting max_input_vars must be >= 5000. For further details, see Environment - max input vars.
* PHP variants: Only 64-bit versions of PHP are supported. Note: Changed since 4.1.
Pretty much the same things should be listed when you go to Server Environment, update the component, then set drop down moodle version pick list to 4.2. Did you do that?
Above also will not interrupt students - or shouldn't ... and if it does, you have an under-powered server!
Guess I have to ask ... why are you NOT staying with long term support version 4.1?
Version Initial release date General support ends Security support ends
4.1 (LTS) 28 November 2022 11 December 2023. 8 December 2025
4.2 24 April 2023. 22 April 2024. 7 October 2024
4.1 (LTS) 28 November 2022 11 December 2023. 8 December 2025
4.2 24 April 2023. 22 April 2024. 7 October 2024
'SoS', Ken