Re: Contemplating drastic change to mount handling

[Earnie Boyd <earnie_boyd at yahoo dot com>]

Christopher Faylor wrote:
> 
> I'm thinking of making a drastic change to mount handling.
> 
> Basically, I'd like to eliminate most of the registry and move mount
> handling into two files: /etc/fstab and /etc/mtab.
> 

Seems familiar.  I seem to remember discussing this with you in the
previous century.

> /etc/fstab would be the same as it is on linux.  /etc/mtab would be a
> binary (trie) representation of the mount table which could be mapped
> into cygwin on the fly, eliminating the need to parse any options.
> 

I need educated on "trie".  Do you mean tree or is it something else?

> We'd still use the registry as a method for finding /etc but that would
> be it.
> 

You could take the approach I did for MSYS and base the root / mount
point on the parent of the directory containing the cygwin1.dll.  It
eliminates the need for the registry entry.  The /bin mount point is the
directory containing the cygwin1.dll.  Both / and /bin and noumount. 
And while you're at it, /bin should be cygexec.  With MSYS I also made
/usr equivalent to / but that could be debatable for Cygwin and don't
have preconceived advice for it's usefulness for Cygwin.

> In this scheme, /etc/mtab would be different than it usually is on unix,
> so maybe it should actually be called something like /etc/bmtab.  It
> would be manipulated only by mount.
> 

Well, you could instead use /proc/mtab.  This protects it from being
modified by some outside source.

-8<-

> I'd also like to get rid of the cygwin method of doing things where if
> you type "mount c:\foo /foo" then the mount is permanent.  I'd like to
> make the mount only exist until the next umount or reboot, like UNIX.
> That doesn't necessarily fall out of this scheme but I have a half
> formed idea of how to handle this, too.
> 
> So, basically the "permanent" mounts would be whatever existed in
> /etc/fstab, maybe with an auto field turned on.
> 

Yep.  Sounds good.

> I don't have this fully fleshed out in my mind yet but I thought I'd
> type out my thoughts here.  This will undoubtedly cause a lot of
> confusion since it is a drastic change.  I would feel a little uneasy
> about making 'mount' impermanent but changing the registry keys doesn't
> bother me at all.  I've been telling people not to directly manipulate
> the registry for years.
> 

Changes are always interesting.  There will always be the extraneous
existing documentation, especially those not controlled by Cygwin that
will cause much grief.

> Oh, and the other thing that would be nice to come out of all this would
> be a generic library that could be linked into other applications (like
> cygcheck and setup) which could manipulate the mount table.
> 

That obviously would be good, would it be mtab it reads or fstab?

You haven't mentioned though the /cygdrive implementation.  For MSYS I
removed the /cygdrive and added automounts for each drive letter.

> Obviously not something for 1.3.13...
> 

Yea, more like something for 2.0.0 even though the ABI is still backward
compatible.  If the ABI remains backward compatible then `cp cygwin2.dll
cygwin1.dll' on installation allows existing cygwin1.dll dependent
binaries to continue to operate.

Earnie.