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I recently did a factory reset to my phone and to my surprise, the operating system remained to the last updated version (6.0.0) and not the version I had when I bought the phone (5.0.0).

Why does this happen? Doesn't a factory reset reset the operating system too?

papakias
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1 Answers1

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System updates overwrite /system. Factory reset wipes /data and /cache but doesn't touch /system. Simple as that.

Andy Yan
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  • can you backup /system to revert to an older version of android? Or is it more complicated than that? – LateralTerminal Oct 31 '17 at 16:37
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    If you have a TWRP backup of an OS older version, it can work - emphasis on "can" because it might not be compatible with the newer baseband, vendor, etc. partitions if the versions are too far apart. – Andy Yan Nov 01 '17 at 00:20