Date: Mon, 13 Apr 1998 00:30:45 +0800 (SGT) From: chas <panda@peace.com.my> To: rotel@indigo.ie, Steve Hovey <shovey@buffnet.net>, freebsd-questions@FreeBSD.ORG Subject: Re: more than 32k users Message-ID: <3.0.32.19980413005259.011936b0@peace.com.my>
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Sorry, this just makes me wonder : If yahoo is using FreeBSD for its services (and I presume that that is its free email service), how could they ramp up to millions of users all supposedly on the same machine (since everyone has the email address : user@yahoo.com). I'm sure they're using IMAPd (beats DB programming for managing folders etc) so they would have had to get around any limit on the number of users on a machine. As for disk-space, my mind boggles. chas >On Apr 11, 8:56pm, Steve Hovey wrote: >} Subject: more than 32k users >> >> I know this has been asked before, but Ill be dipped if I can find the >> answer. >> >> Is it possible to increase the maximum number of unix ids over 32k so that >> one can have over 32k users in /etc/passwd? > >>From looking at the header files I see that uid_t (the data type >used to represent the UID in the kernel and elsewhere) is an unsigned >32 bit integer meaning that this is possible in theory as long as >no programs have assumed anything about the size of uid_t. pwd_mkdb >doesn't like UID's > USHRT_MAX, but will allow you to use them. > >I have created a user with UID = 100000, and it certainly doesn't >break anything instaneously :) > >[root@ginseng /etc]# tail -1 /etc/passwd >foo:*:100000:100000:Niall Smart,Somewhere Someplace:/home/nsmart:/usr/local/bin/zsh >[root@ginseng /etc]# su foo >[foo@ginseng /etc]$ id >uid=100000(foo) gid=100000 groups=100000 > >You might like to ask in -hackers about this, if you're in an >environment where you can experiment with this then I'd so go ahead >and try it. > >Beware that any programs which do not use uid_t portably (i.e. >assume it can only go up to 65536) will probably have security >problems if you use uid's > 65536 because the variable they >store the UID in will wrap around. > >So, in summary, there is nothing preventing this on the kernel >side and correctly written programs should handle it, but be >careful - try and find someone else who is doing this! :) > >Niall > >-- >Niall Smart. Microsoft Suck. See www.freebsd.org for details. >echo "#define if(x) if(!(x))" >> /usr/include/stdio.h > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-questions" in the body of the message > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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