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Re: merged-/usr vs. partially-symlink-farmed-root



* Ansgar <ansgar@43-1.org> [210822 05:08]:
> Hi Guillem,
> 
> On Sun, 2021-08-22 at 00:11 +0200, Guillem Jover wrote:
> > There was talk about the huge amount of symlinks required in a
> > symlink farm setting, but that might have been true for a scenario
> > where those symlinks would have been handled automatically and
> > transparently.
> 
> To get a filesystem layout equivalent to merged-/usr via symlinks
> farming *every* package shipping files in at least /usr/bin, /usr/sbin
> and possibly some of /usr/lib would need to include symlinks in /bin,
> /sbin, /lib.  This would affect far more packages than updating the
> packages currently shipping files in /bin, /sbin and /lib* to ship
> these under /usr instead.

It is true that for a symlink-farm-usr-merge system to be strictly
equivalent to a symlink-dir-usr-merge system, many packages that never
had /bin/foo but had /usr/bin/foo would have to add a symlink /bin/foo,
however this is clearly unnecessary.  The problem that the symlink farm
is solving is that scripts (distributed or user-written) that depend on
/bin/foo need to continue to work on a partially merged system.  A
previous message (already deleted, so I'm not sure from whom) clearly
identified 240 packages (number pulled from memory, so might be off)
that would have to put symlinks in /bin and /sbin for the
symlink-farm-usr-merge strategy to work.

The amount of work is orders of magnitude less than you are
representing.  There is no need for the symlink-farm to exactly match
the symlink-dir solution.  The union of systems during the symlink-farm
merge and systems after the merge is complete can _only_ count on
/bin/foo existing if it existed before the merge was started.  There is
no need for anything else (wrt /bin/foo existing).

...Marvin


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