How to reinstall os without losing data?

sylvain198 wrote:

Hi, how to reinstall os without erasing Hard Drive and losing data, as Time Machine doesn't work, I have no backup. Thanks

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

You have choices here— choose wisely.

Do not wait for a catastrophic failure to 'get' the backup religion if you value your user data.

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

—Boot clone https://discussions.apple.com/docs/DOC-10081

—How to use Time Machine to back up or restore your Mac: https://support.apple.com/en-us/HT201250

—Use DiskUtility Restore feature https://support.apple.com/guide/disk-utility/restore-a-disk-dskutl14062/mac

note: >System Preferences>Security & Privacy >Privacy>Full Disk Access

unlock the padlock, press the + button and add Disk Utility

There is always the risk of losing data when doing a major operation like reinstalling an operating system. Something could go wrong. Follow the instructions provided and you should be OK, but there is no safer way that by performing a backup regularly and often.

From Cold Boot ( Off ) power up and immediately Hold Command + R keys. Will need a good internet connection. Once booted to Recovery Mode will be offer several options. Choose Reinstall macOS.