Messages in this thread | | | Subject | Re: uids | Date | Wed, 16 Jun 1999 15:40:22 -0700 | From | Jim Dennis <> |
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> Jim Dennis <jimd@starshine.org> writes:
[... does Linux support 32-bit UIDs and GIDs ? ...]
>> So I don't think that large UIDs are supported on any >> port of Linux; nor by glibc 2.0 nor 2.1.
>> I've copied Ulrich Drepper <drepper@cygnus.com>, current >> maintainer of glibc, on this reply in the hopes that he'll >> set me straight if I'm wrong. Ulrich?
> drepper@myware glibc-devel-19990613$ egrep > '[gu]id_t' /usr/include/bits/types.h > typedef __u_int __uid_t; /* Type of user identifications. */ > typedef __u_int __gid_t; /* Type of group identifications. */
> Glibc never used 16 bits values.
It's getting the type from the OS header files (in this case the Linux types.h), right?
This suggests that one could make a kernel with 32-bit UIDs and GIDs, rebuild glibc on it (and possibly have to fix bugs some applications that were linked against glibc) and build a Linux system with support for the larger UID space.
I'll ask on the kernel list regarding the size/scope of such a change. Would it require changes to various filesystems? (I presume so, since they are storing UIDs and GIDs in all of the inodes which seem to be a pretty densely packed struct. I guess that shifting things around in the inode my cause sector/cluster alignment problems).
Obviously any statically linked utilities the depended on these structures would also have to be rebuilt.
I discussed this at least once before (on a mailing list newsgroup or somewhere) and came away with the impression that it is a pretty big project.
I've moved this discussion to the kernel list (moving Ulrich and M off to a Bcc: line so they will not be inundated with responses therefrom). I'll summarize any fruits of that thread back to both of them.
So, LKern-at-large:
How big a project would this be? Are larger UIDs supported under any version of Linux? How much would be break if we tried it? Why do we currently use only 16-bits? Do the UID/GIDs pack into some other struct better that way? Does it have to do with real UID vs effective UID?
TIA for any comments.
-- Jim Dennis jdennis@linuxcare.com Linuxcare: Linux Corporate Support Team: http://www.linuxcare.com
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