MSDOS Filesystem question related to "read-only" files

Karl Denninger karl at
Mon Nov 20 15:37:37 UTC 2017

I'm running into an interesting issue here and wondering if there's a
way to do this under FreeBSD.

MSDOS filesystems have a "primitive" permission capability;
specifically, they can have a "Read-only" attribute on a file.  It looks
like OpenBSD supports this from reading their man pages.

FreeBSD doesn't appear to.  When you mount a msdos filesystem (e.g. a
USB stick) whoever owns the parent directory where you mount it gives
you the permissions and "ownership" of files on said filesystem.  All
good so far.  But attempting to chmod a file to remove write permission
"succeeds" (returns success) but does nothing.

Is this capability simply not present on FreeBSD?  I'm interested in
using it as a means of "flagging" files on a USB stick in an application
that I do not want to remove if the stick fills (basically, to "protect"
them from being aged off) and it appears there's no way to do it, other
than to use something unique in the filename that I would then have to
pay attention to.

Karl Denninger
karl at <mailto:karl at>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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