How to solve the disk cannot be used to startup your computer

please use this command to download catalina
softwareupdate --fetch-full-installer --full-installer-version 10.15.7

[@theadventurer7259]

I updating to Big sur and the same thing happened. Can I use this method

[@RasKalevthesouljourner]

Uhh what if it’s El Captain does the code change?

[@naveedshah4914]

Will this wipe all the data in my hard drive? Will I lose all my files on my current hard drive?

[@JinusTechVideos]

Yes.u r changing the file system

[@Khadolkacha]

Thank you!