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I have several questions about linux groups

  1. Is there a limit to the number of groups a user can create?
  2. Is there a limit to the total number of groups in a system?
  3. Is there a limit to the number of groups a user may be a member of?
  4. Do large numbers of groups (and users as well) degrade performance? Will 1000 users with 1000 groups each be substantially slower than 1 user and no groups (discluding system generated users/groups)

I'm trying to come up with a website that bridges the gap between SQL user databses and actual linux users.

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up vote 5 down vote accepted
  1. Users can't create groups, only the superuser can. And the superuser can create up to the system maximum minus existing groups.

  2. Modern Linuxes have a 32-bit gid_t, so just short of 4.3e9.

  3. Depends completely on the NSS being used. I don't think the files NSS has a limit.

  4. Again, depends on the NSS. Using something like LDAP would be faster than files obviously.

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How do I find out what my 'system maximum' is. I read here it is 16 or 32...that is pitiful if it's the case. – puk Nov 4 '11 at 5:00
Why are you reading Solaris documentation when you've tagged the question "linux"? – Ignacio Vazquez-Abrams Nov 4 '11 at 5:07
that's a relief, but the article says You simply cannot have more than 16 groups and use AUTH_SYS. It seems the problem is more complicated than at first glance. – puk Nov 4 '11 at 5:10
I got linked to that page from another linux site. – puk Nov 4 '11 at 5:11
So then don't use NFSv2 or v3. – Ignacio Vazquez-Abrams Nov 4 '11 at 5:13

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