I have a MBP with a 1 terabyte SSD. If I look at the storage tab of about this mac, it looks like I would expect, but if I run df -h from the terminal, I get:

Filesystem       Size    Used   Avail   Capacity   iused       ifree         %iused  Mounted on
/dev/disk1s1s1   932Gi   14Gi   83Gi    15%        568975      9767409185    0%   /

Is this a bug in df on Big Sur, or should I be worried that something is up with my MBP? On my old computer (which never get past Mojave) the numbers added up and looked right.


You should not be worried. There is no bug.

You should show all the output from df -h | grep disk1s. The line with disk1s1s1 refers to the currently used snapshot of the read-only boot volume. In which case the 14Gi is the expected used.

  • Thanks! Is that new in Big Sur (or perhaps in something after Mojave)? – Ben Holness Feb 16 at 3:57
  • Catalina did some of it and Big Sur has done more. The system/boot volume is now divided into two - a readonly part (~14GB) and a read/write part. The readonly part can only be modified by a macOS install - or the user with a great deal of difficulty. There are now more Volumes in the APFS Container. 'diskutil list' shows all these. The boot process has become more complex and has differences between Intel without T2 chip, Intel with T2 and Apple Silicon (M1). – Gilby Feb 16 at 4:23

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