[Nix-dev] Why is the /nix/store location hardcoded?

[Jeff Johnson]

On Apr 21, 2010, at 6:51 PM, David Soergel wrote:

> Is there some compelling reason why the location of the nix store is fixed at compile time, and why nix-push/nix-pull can only work among machines that agree on the location of the store?
> 

Sure -- FHS and "Have it your own way!" paths lead to complexity
for no important gain. Go read D.J. Bernsteion's reasoning with
(the very in your face, ymmv) the restrictive qmail licensing.

If you read through http://cr.yp.to you will also find djb's
package management proposal based on "/package" hardwired much like "/nix/store"
is hard-wired. No instances, and no "functional package management", but
the same basic idea:
	Path prefixing breaks software needlessly.

> I'm guessing the trouble is that the .drv files contain absolute paths, so the closure hash is sensitive to the store location.  But all of the paths begin with the store path anyway, so why not just keep them relative?  Then the store location could be provided at runtime, could be in a user's home directory (not requiring root access as "/nix/store" does), and channels would work anyway, since the derivation hashes would be consistent.
> 

Yep. But because there's _ALWAYS_ a Nix instance attached to
all data in "/nix/store", there's literally no reason why the
"/nix/store" prefix matters much. Its the instance hash, not the
path prefix, that is essential.

(aside, total guesstimate)
You likely (untested, I haven't yet looked) can achieve "/nix/store" prefix
independence by generating your nix instances slightly differently,
without the "/nix/store/" prefix, or substituting any token for "/nix/store"
everywhere you try to generate a Nix instance. I doubt the plain test
hashes generated by nix-hash care too much. The hack to substitute
a token for the literal "/nix/store" prefix is very not hard, but
there's likely some deeper reasons why "/nix/store" _MUST_ be
used as a prefix. But I digress, there's simply no reason imho
to substitute a token for the literal "/nix/store" prefix token, it adds a huge
amount of complexity for no demonstrable gain.

Disclaimer(s):
	I am a djb (and increasingly, Nix+Eelco ;-) fan-boy.
	JMHO, YMMV, everyone's does.

> That seems to me like the conventional way to do things-- what am I missing?  Thanks for any insights,
> 

hth

73 de Jeff