Do I need to know Linux to administer CiviCRM?
The question is tricky because it's a bit imprecise -- different people may interpret "know Linux" and "administer CiviCRM" a bit differently.

It might be clearer to rephrase the issue this way:


To administer the data model, profiles, contacts, events, mailings, etc, you need an analytic mindset and a general understanding of data-management, but you do not need sysadmin skills.
To administer the installation, backup, or upgrade, you do need sysadmin skills (for HTTP/MySQL/PHP on your chosen platform). For a general GNU/Linux hosting platform with Ubuntu/Redhat/etc, general GNU/Linux skills should do. For Windows or cloud platforms, you probably need more advanced/niche skills.


Additionally, there are the wildcards -- adding new features or perfecting the appearance within your site or debugging hard problems. These are wildcards because the required skills vary widely. Sometimes basic point-and-click will do; sometimes you need robust skills in a dozen systems.

As others have mentioned, a good model is to partner with someone more experienced. You can handle a lot of administration yourself -- and when/if a task comes up which needs more skills, reach out to them.