If you are working on a web application that runs in a browser, you don't have to know much about Linux administration, but chances are there will be some configuration (setting up virtual hosts) that needs to be done on the server. So some knowledge of Linux administration is useful but not essential.
For most backend developer jobs, you don't need to know much about Linux beyond installing software packages using apt-get or yum and editing config files like httpd.conf or my.ini.
You must have a good hold over the command line because you will run git commands at the command line and install pip packages. You will also be using your IDE from the command line and deploying applications to staging and production systems using scripts that you run from the command line.
If you are not used to working at the command line, it can be an intimidating experience. But it's one of those skills which improves with practice and once you get past the initial "I'm not used to this" stage, you'll find that being comfortable with the shell is actually quite useful.
The biggest thing that you need to know about backend developer jobs is how to avoid the obvious security pitfalls, especially if you are working with sensitive data. If you work with AWS, it's good to know how to set up security groups and IAM roles,
There are some basic things you need to know just to get going
How to navigate the filesystem
How to edit files (I recommend nano for beginners)
How to perform basic file operations such as cat, rm, cp, mkdir, rmdir
How to operate with environment variables (PATH and friends)
How to download files using curl or wget
How to install software using your distro's package manager
Read more: https://eiliana.com/blogitem/plenty-of-automation-testing-jobs-are-you-ready-to-get-the-best