What is standard way to do this or just override files?
It's same as magento 1.9?
Whats care should be taken before and after upgrading?
Best Answer
I don't know exactly, what you want to do, so I'll try to guess. If it's not what you're asking about, please clarify your question.
Update an existing theme
If you did correct errors in the theme and you want to go live with the patched version.
Just override the files in app/design/frontend/[Theme Author/Vendor]/[Theme Name].
Tell Magento about the new files. This depends on your mode and cache settings:
Development mode: If your Magento cache is disabled, you don't have to do anything and the changes should be live instantly.
Otherwise, you have to clear all (affected) caches either via administration panel or with Magento CLI command ./magento cache:clean.
Production Mode: You only have to run ./magento deploy:mode:set production to set Magento into temporary maintenance, deploy all files, clear caches and reactivate production mode afterwards.
Profit!
Edit an existing theme
If you want to have some corrections on an already existing theme.
Create new folders in app/design/frontend, so that you have app/design/frontend/[Your Name]/[Theme Name]
Instead of overriding files in existing theme, just create/copy them with the same directory structure within your theme and apply the changes (you only have to copy the files you want to change).
As this is a very short guide on adding a new theme, please read the documentation linked above with all linked documents (the ones in the left sidebar, too) to understand Magento theming correctly.
Note: Magento CLI
You have to run all commands as your Magento file system owner! Otherwise, Magento won't/can't use them.
Best Answer
I don't know exactly, what you want to do, so I'll try to guess. If it's not what you're asking about, please clarify your question.
Update an existing theme
If you did correct errors in the theme and you want to go live with the patched version.
Just override the files in
app/design/frontend/[Theme Author/Vendor]/[Theme Name]
.Tell Magento about the new files. This depends on your mode and cache settings:
Development mode: If your Magento cache is disabled, you don't have to do anything and the changes should be live instantly.
Otherwise, you have to clear all (affected) caches either via administration panel or with Magento CLI command
./magento cache:clean
../magento deploy:mode:set production
to set Magento into temporary maintenance, deploy all files, clear caches and reactivate production mode afterwards.Edit an existing theme
If you want to have some corrections on an already existing theme.
app/design/frontend
, so that you haveapp/design/frontend/[Your Name]/[Theme Name]
As this is a very short guide on adding a new theme, please read the documentation linked above with all linked documents (the ones in the left sidebar, too) to understand Magento theming correctly.
Note: Magento CLI
You have to run all commands as your Magento file system owner! Otherwise, Magento won't/can't use them.