linux limits

Posted on 1999-01-09
Last Modified: 2013-12-15
I would need to know how many user linux may accomodate and if the usernumber in passwd must absolutely be in sequence or without gaps and if there is a limit to its value (can it be a figure over 32xxx)? In other words may I use a user number from an external registration database to build passwd files for several linux machine ? (I do not use add).
Question by:toulon
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Author Comment

ID: 1632095
Edited text of question
LVL 51

Expert Comment

ID: 1632096
theoretically the number of users is limited to the ushort (whatever this range is on your hardware).
But in practice its limited to 65536, which is the max. UID to be assigned in passwd. Keep in mind that some UIDs are reserved for system usage (all <1000).
Yes it may have gaps, and no need for sequence (without gaps).
Yes you may use a number from externbal registration (for example LDAP), just take care that you don't get duplicates.

Author Comment

ID: 1632097
Great! But I have not the option to grade it. Is there a bug with
the system?
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Expert Comment

ID: 1632098
ahoffmann is correct, most systems are using a unsigned shot to UID, but you can use the same UID to external users ( to dial-in authentications for exemple)....
LVL 51

Expert Comment

ID: 1632099
well I think toulon want's to grade my comment, cox.
toulon, please reject cox's answer (sorry), and I'll post another one.

Anyway, cox, did you mean that I can use duplicate UID if I assign them to users
which cannot login (for example because of /usr/bin/false in passwd), or is it just
because your system only allows one dial-in connection?

Author Comment

ID: 1632100
Response goes to ahoffman.
However I did not understand the remark of cox, nor the comment of ahoffman, while it rises interest. Would you be so kind as to explain to a low IQ Frenchy somewhat lost with cryptic English.
LVL 51

Accepted Solution

ahoffmann earned 100 total points
ID: 1632101
answer is my very first comment.

Author Comment

ID: 1632102
ahoffman. I agreed the question. Now I see it rated 10 only. Did you get the 100 ?
LVL 51

Expert Comment

ID: 1632103
got it, thanks
(10 is what others have to "pay" for it now)

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