I understand that writing a Linux Mint image to a USB drive usually erases the drive's existing contents. I want to use an NVMe SSD in an enclosure as the drive where I install and run Linux. Will the initial installation or flashing process erase everything on that SSD, or can I install Linux while preserving files that are already stored on it?
3 Answers
Linux will erase whatever you tell the installer to erase. If you select the full-disk or automatic installation option, the SSD's existing partitions and files will usually be removed. To keep data, back it up elsewhere and use manual partitioning only if you’re confident identifying the correct drive and partitions.
If you’re new to Linux, try it in a virtual machine first using software such as VirtualBox or Hyper-V. It lets you learn the basics without risking your files. When you’re ready to install it on the external SSD, double-check the selected disk and choose a manual or custom partitioning setup if you need to preserve existing data.
Assume the installation can erase the entire SSD. The installer may offer options for dual booting, manual partitioning, or using only available space, but choosing the default automatic setup can wipe the whole target disk. Back up anything important before starting.

That makes sense—I’ll make a backup first rather than relying on the installer to preserve anything.