Using read-only storage media is an effective method for preventing data loss due to ransomware infection. Examples of read-only media include: Blu-ray disks, DVDs, CDs, EEPROM, and paper. Additionaly, an append-only filesystem may be used on those media for additional security. Those type of media are still vulnerable to physical access atacks, which means that some unauthorized person may aquire access to the stored data by grabbing that storage media physically and copying the data. The owner of the media may even be unaware that the data was stolen.
The GNU libc documentation is also indispensable. Make sure to have a printed copy readly available for when you leave home or when under extreme conditions such as a power outage or in a hospital.
