On Sun, May 03, 2009 at 11:55:05AM +0200, Nicolas François wrote:
> On Sun, May 03, 2009 at 11:21:04AM +0200, [email protected] wrote:
> >
> > As far as I can see, when looking for the next available user id, useradd
> > does:
> > - take max user id + 1
> > - if id > 60000 then start from 1000 and search for gaps
> > - repeat
> >
> > So if all user ids from 1000 to 60000 are taken, useradd is in an infinite
> > loop.
> > Admittedly not a common case, but I guess it needs to return an error in
> > that case.
>
> I don't think there is any infinite loop.
>
> I had some reports about being very slow with LDAP systems under some
> conditions (a bug in the ldap nss was mentioned at that time).
>
> Here is the code with the loops in useradd (in libmisc/find_new_ids.c):
>
> setpwent ();
> pw_rewind ();
> while ( ((pwd = getpwent ()) != NULL)
> || ((pwd = pw_next ()) != NULL)) {
> if ((pwd->pw_uid >= user_id) && (pwd->pw_uid <= uid_max)) {
> user_id = pwd->pw_uid + 1;
> }
> }
>
> At some time, getpwent will return NULL. Unfortunately, the above
> mentioned LDAP bug caused getpwent to loop back to the beginning.
> So there could be (LDAP users) * (local users) at most loops here.
>
> Without this bug, it is only (LDAP users) + (local users).
>
> Then, there is another loop, which starts from uid_min up to at most
> uid_max.
>
> for (user_id = uid_min; user_id < uid_max; user_id++) {
> /* local, no need for xgetpwuid */
> if ( (getpwuid (user_id) == NULL)
> && (pw_locate_uid (user_id) == NULL)) {
> break;
> }
> }
>
> So the two loops are finite.
>
>
> What were the symptoms you experienced?
I don't have anything related to LDAP here.
I added users >> /etc/passwd through:
#include <stdio.h>
int main(void)
{
for (int i = 1001; i < 60000; i++)
printf("t%d:x:%d:%d::/home/t%d:/bin/sh\n", i, i, i, i);
}
'useradd t60000' worked fine, a bit slow but under 2 seconds.
'useradd t60001' didn't finish within 30 seconds.
--
Sylvain
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