mount.posixovl(8)

💖 mount.posixovl — the manual, but make it make sense

okay bestie, gather round, because we're talking about mount.posixovl(8) — a FUSE file system, a real one, and she's serving POSIX. 💅

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✨ NAME ✨

posixovl — a FUSE file system that provides POSIX functionality. yes that's the whole vibe. she makes non-POSIX things act POSIX. iconic behavior honestly.

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🎀 SYNOPSIS 🎀

mount.posixovl [-F] [-S SOURCE_DIR] TARGET_DIR [-- fuseopts]

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🦋 DESCRIPTION 🦋

so here's the tea 🍓 — if you don't give her a source directory, then TARGET_DIR is doing double duty and specifies both the source and the target (aka the mount point). that lil setup is called an "over mount". slay.

here's what she supports, no cap:

• chmod
• chown
• hardlink
• mkfifo
• mknod
• symlink/readlink
• ACLs/xattrs — but only in passthrough mode, there is no emulation. periodt.

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🔥 NOTES 🔥

okay this is the part where you actually pay attention, bestie. 👑

if you use posixovl on a file system that's already POSIX-behaving (looking at you, XFS), you're gonna get some issues, because telling whether a path is POSIX behaving or not is genuinely difficult. so here's the decision that was made:

• permissions will be set to the default permissions (see below) unless a HCB is found that can override these
• all lower-level files will be operated on/created with the user who initiated the mount

so if no HCB exists for a file or directory, the default permissions are 644 and 755, respectively. the owner and group of the inode will be the owner/group of the real file. that's just how it is 💅

also!! every non-regular, non-directory virtual file gets a zero-size real file. it simplifies handling, and it makes it apparent the object exists when using another operating system. lowkey genius.

and the command df(1) will show you this:

$ df -Tah
File System    Type    Size  Used Avail Use% Mounted on
/dev/hda5     vfat    5.9G  2.1G  3.9G  35% /windows/D
posix-overlay(/windows/D)
     fuse.posixovl    5.9G  2.1G  3.9G  35% /windows/D

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⭐ OPTIONS ⭐

• -F — option -F will disable permission and ownership checks that would be required in case you have a POSIX mount over VFAT. for example, where /vfat is vfat, and /vfat/xfs is a POSIX-behaving file system. (and yeah, the synopsis also shows -S SOURCE_DIR — that's the source dir situation we were yapping about in DESCRIPTION 🫶)

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🌸 EXAMPLES 🌸

in general, posixovl does not handle case-insensitivity of the underlying file system (in case of VFAT, for example). so if you create a file X0 on VFAT, it's usually lowercased to x0, which may break some software, namely X.org. 😭

in order to make VFAT behave more POSIX-like, the following mount options are recommended:

mount -t vfat /dev/sda5 /mnt/vfat -o check=s,shortname=mixed

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💜 ENVIRONMENT 💜

None. literally nothing. empty. she doesn't need env vars, she's self-sufficient 💅

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🧚 FILES 🧚

None. also nothing. we love a low-maintenance queen.

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🌈 SEE ALSO 🌈

mount(1) umount(1)

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👑 AUTHORS 👑

program was written by Jan Engelhardt <jengelh@users.sourceforge.net>. 🫶

this manual page was written by Jari Aalto <jari.aalto@cante.net>, for the Debian GNU system (but may be used by others). released under license GNU GPL version 2 or (at your option) any later version. for more information about license, visit <http://www.gnu.org/copyleft/gpl.html>.

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and that's the whole page, bestie — signed off from the mount.posixovl manual, dated 2026-01-20, no notes, only vibes. go mount something ✨💖