--one-file-system: add macOS apfs notes, fixes #4876

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Thomas Waldmann 2023-04-02 15:31:37 +02:00
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1 changed files with 7 additions and 7 deletions

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@ -635,13 +635,13 @@ class CreateMixIn:
The ``-x`` or ``--one-file-system`` option excludes directories, that are mountpoints (and everything in them).
It detects mountpoints by comparing the device number from the output of ``stat()`` of the directory and its
parent directory. Specifically, it excludes directories for which ``stat()`` reports a device number different
from the device number of their parent. Be aware that in Linux (and possibly elsewhere) there are directories
with device number different from their parent, which the kernel does not consider a mountpoint and also the
other way around. Examples are bind mounts (possibly same device number, but always a mountpoint) and ALL
subvolumes of a btrfs (different device number from parent but not necessarily a mountpoint). Therefore when
using ``--one-file-system``, one should make doubly sure that the backup works as intended especially when using
btrfs. This is even more important, if the btrfs layout was created by someone else, e.g. a distribution
installer.
from the device number of their parent.
In general: be aware that there are directories with device number different from their parent, which the kernel
does not consider a mountpoint and also the other way around.
Linux examples for this are bind mounts (possibly same device number, but always a mountpoint) and ALL
subvolumes of a btrfs (different device number from parent but not necessarily a mountpoint).
macOS examples are the apfs mounts of a typical macOS installation.
Therefore, when using ``--one-file-system``, you should double-check that the backup works as intended.
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