mount.posixovl [-FH] [-S source_dir] target_dir [-- fuse_opts]
posixovl provides a filesystem view that supports various POSIX opera‐
tions while using an otherwise incapable lower filesystem. Filesystems
of various degrees of POSIXness can be utilitzed. VFAT is a common
denominator when it comes to cross-compatibility, though NTFS — its
features are unused in Linux — would be another possibility. Secondly,
potent native POSIX-style filesystems can also be used, though the
actual use of doing that remains to be discovered.
If no source directory is given, the target directory specifies both
source and target (mountpoint), yielding an "overmount".
-F Disable permission and ownership checks on the lower filesystem.
Normally these would be used to check for POSIX filesystems
mounted inside a non-POSIX tree. (For example, where /vfat is
vfat, and /vfat/xfs is a POSIX-behaving filesystem.)
-H When this option is enabled and a hardlink in the posixovl
namespace is created, the contents of the file will be repli‐
cated in the lower filesystem rather than using zero-sized
placeholder files. Note that the replicas will not be updated
later on when editing the inode through posixovl.
posixovl will emulate the following calls if the lower filesystem is
incapable of supporting these operations:
· chmod
· chown
· hard links
· mkfifo
· mknod
· symbolic links
The following currently only work in passthrough mode (when using a
lower filesystem that already supports these):
· Linux ACLs/xattrs
Missing suppot:
· Case-sensitivity
Using posixovl on an already POSIX-behaving filesystem (e.g. XFS)
incurs some issues, since detecting whether a path is POSIX behaving or
not is difficult. Hence, the following decision was made:
· permissions will be set to the default permissions (see below)
unless a HCB (hidden control block, the metadata files for
posixovl) is found that can override these
· all lower-level files will be operated on/created with the user who
inititated the mount
If no HCB exists for a file or directory, the default permissions are
rw-r--r-- or rwxr-xr-x, respectively. The owner and group of the inode
will be the owner/group of the real file.
Each non-regular, non-directory virtual file will have a zero-size real
file. (Simplifies handling, and makes it apprarent the object exists
when using other operating systems.)
`df` will show:
$ df -Tah
Filesystem 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
In general, posixovl does not handle case-insensitivity of the underly‐
ing filesystem (in case of vfat, for example). If you create a file
"X0" on vfat, it is 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/hda1 /windows/D -o check=s,shortname=mixed
posixovl and this manpage were written by Jan Engelhardt.
Development of posixovl was sponsored by Slax (http://www.slax.org/).
This github repository is a fork of
https://sourceforge.net/p/posixovl/posixovl