I am running macOS High Sierra.
I was wondering how system services (e.g. Time Machine with the protected backup directories) could modify the directories that
root cannot access. I was trying to modify the backup directory premissions to allow Read/Write access to all users (with
root) and got this output (I had to replace my computer name with asterisks for privacy reasons):
*****:Time Machine root# chmod -R 0777 Backups.backupdb/ chmod: Unable to change file mode on Backups.backupdb//.RecoverySets/1/com.apple.recovery.boot/boot.efi: Operation not permitted chmod: Unable to change file mode on Backups.backupdb//*****: Operation not permitted [...]
However, Time Machine can tamper with the files even though
root can not.
I know that in the Get Info dialog is says that the user
system can have Read/Write access.
Is is even possible to have a user be able to access a file when
root can not or is is just Apple indicating that the system can access it?
UPDATE: I have been notified that Time Machine backups are a different story altogether with Time Machine Backup Protection. However, I still don’t know about how System Integrity Protection doesn’t block other things (e.g. Updates from the App Store).