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1994-09-02
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The compressed tar file fss.tar.Z contains a few examples and comments that
pertain to the File System Switch facilities in SCO UNIX. Remember,
this is unsupported, and probably dangerous stuff. Use at your
own risk.
File System Switch (FSS) is an interface which allows
custom file systems to be added to a UNIX System V release 3
system.
In order to implement a custom filesystem, you must write
a number of filesystem dependent routines which interface
with a filesyetem independent layer in the UNIX kernel.
The custom filesystem module itself is linked into the
UNIX kernel in a manner similar to a hardware device driver.
A detailed description of the installation of a custom
filesystem is outside the scope of this document, however
here is a summary of the necessary configuration files.
(For the purposes of this discussion it will be assumed
that the file system to be added is the "XYZ" filesytem
and that the names of all of the filesystem dependent
routines have the prefix "xyz".
The following files and directories have to be supplied:
/etc/conf/pack.d/xyz/Driver.o - the XYZ filesystem support
module itself
/etc/conf/pack.d/xyz/space.c - space.c file for the XYZ
filesystem
/etc/conf/mfsys.d/xyz - XYZ filesystem master configuration
file
/etc/conf/sfsys.d/xyz - XYZ filesystem system configuration
file
The format of the mfsys and sfsys files is documented in
the manual pages for MFSYS(F) and SFSYS(F) respectively.
The function of the mfsys file is to declare the name of
the filesystem, the prefix which is added to the name of
each filesystem dependent routine, two sets of flags and
a bitmask of ones and zeroes which defines which filesysytem
dependent routines are actually implemented in this particular
filesystem.
The sfsys file is used to indicate whether the filesystem
should actually be configured into the kernel.
Typically the space.c file will be used to define storage
for filesystem dependent data structures such as the
filesytem "super-block" (or equivalent) and filesystem
dependent "inode" structures or equivalent.