On Mar 5, 2009, at 2:56 PM, Nigel Kersten wrote:
>
> :maximum_uid => [4294967290, "The maximum allowed UID. Some
> platforms use negative UIDs
> but then ship with tools that do not know how to handle
> signed ints, so the UIDs show up as
> huge numbers that can then not be fed back into the
> system. This is a hackish way to fail in a
> slightly more useful way when that happens."],
>
> So this is a problem on OS X, and I only just noticed it.
>
> $ dscl . read /groups/nobody PrimaryGroupID
> PrimaryGroupID: -2
>
> $ ruby -e "require 'etc'; puts Etc.getgrnam('nobody').gid"
> 4294967294
>
> $ id nobody
> uid=4294967294(nobody) gid=4294967294(nobody)
> groups=4294967294(nobody)
>
> Obviously we can work around this by increasing maximum_uid, but I'm
> wondering why we have this setting at all? Is there some other problem
> it solves that I'm not aware of?
>
> At least on OS X, the reverse process works fine.
>
> # ls -l /tmp/foo
> -rw-r--r-- 1 nigelk wheel 13 Mar 4 14:36 /tmp/foo
>
> # chgrp 4294967294 /tmp/foo
>
> # ls -l /tmp/foo
> -rw-r--r-- 1 nigelk nobody 13 Mar 4 14:36 /tmp/foo
The problem is that some tools give -2 as the UID and other tools
gives 4 quadrillion as the UID, so we always consider them out of sync
and do stupid things.
Most likely, the right approach here is to use dscl for both reading
and writing, rather than relying on any Ruby tools.
Here's a good demonstration of where it all goes to hell in a
handbasket. This code:
#!/usr/bin/ruby
require 'etc'
File.open("/tmp/testing", "w") { |f| f.puts "eh" }
uid = Etc.getpwnam("nobody").uid
File.chown(uid, nil, "/tmp/testing")
-----------------
Fails with:
l...@phage $ sudo test.rb
/Users/luke/bin/test.rb:8:in `chown': bignum too big to convert into
`long' (RangeError)
from /Users/luke/bin/test.rb:8
l...@phage $
So you can't use the same value end to end.
Yes, (I assume) we could build a complicated system to switch between
signed and unsigned ints. Or, we could just stick our fingers in our
ears, say "nyah nyah" a hundred times, and act like it's not a real
problem.
At this point, it happens so rarely that the latter has been at least
acceptable.
--
To my embarrassment I was born in bed with a lady.
--Wilson Mizner
---------------------------------------------------------------------
Luke Kanies | http://reductivelabs.com | http://madstop.com
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