Q:

The value you set has already been locked. To change the value, use the --lock-env option

I'm trying to do
php -f bin/magento config:set dev/js/enable_js_bundling 1

But I get:

The value you set has already been locked. To change the value, use the --lock-env option.

What does this mean and how can I achieve what I want?

A:

It seems you have locked the admin / configuration changes using the app:config:set command. Now the only option you have is to make necessary changes in your config.php.
Entries would be like:
 'js' => [
                'merge_files' => '0',
                'minify_files' => '0',
                'minify_exclude' => '
                /tiny_mce/',
                'session_storage_logging' => '0',
                'translate_strategy' => 'dictionary',
                'enable_js_bundling' => '0',
            ],
            'css' => [
                'minify_files' => '0',
                'minify_exclude' => '
                /tiny_mce/
            ',
                'merge_css_files' => '0',
            ],

Set values to 1 where you want to enable minification / merging and save this file. After saving run the php bin/magento app:config:dump command. 

