PLEASE HELP I missed with the build.prop file but I made a copy of it before.Then I deleted the edited build.prop file and restore the old one then rebooted the phone(Samsung S3 lineage 14.1) but not working!IT shows the Samsung logo then black screen appear.I can access the TWRP so I checked that the old build.prop file is in /system but nothing.What should I do? pls help
If you can access TWRP and you're on lineage. That means that you flashed a custom OS on the phone.
Same way you can get a fresh copy of build prop from the extracted firmware that you flashed because TWRP mainly flashes zip files. Zip files are generally easily extractable by programs like WinRAR.
After getting the build prop from the zip. Copy it to the phones internal storage using a PC while still on TWRP. Then use TWRP native file manager to copy the build.prop to /system/ so that the file address is /system/build.prop and use TWRP chmod option to set the permission of the file to 0644. Reboot the phone and enjoy.
Alternatively you can try to edit the current build.prop if you have the ability to interpret build.prop commands. And then copy it to the phone as similarly as above.
If nothing works here. Just reflash the Lineage OS, clear user data and cache and it will boot as freshly as it once was
Talking about permission 0644, this is a permission that means the owner of the file can read and write the file but, group and others can only read information from it.
When you want to calculate the number, you should understand that this is a 3-digit number for Owner + Group + Everybody respectively (each digit of the number)
The highest value of each digit totals to is 7 to mean all permissions are granted and it can be calculated as 4 (read) + 2 (write) + 1 (execute). 644 means owner has read write access, while others read only
The file is not executable and that's why owner has 6 (4 read + 2 write ) instead of 7 ( 4 read + 2 write + 1 execute)
The leading digit is "always" 0 and it is used for special permissions only
Even though other firmwares can read without this permissions, that is if the permission is less restrictive like 0755, it's safe to set the permission manually to ensure that when the file was written to system, it doesn't have a restrictive permission like 0000 where nothing not even the file owner can read from it