As stated some time ago, I had the problem that users vanished after some time.

As I get a lot of e-mails regarding this problem, I therefore documentate here the details I've found out so far:

Ncsd works unreliable

Yes, indeed, switching off nscd removes the problem.

But there are more problems I experienced with nscd:

  • Sometimes it consumes 100% cpu (and does not stop that until being killed)
  • Sometimes it just crashes.
  • Sometimes it causes users to "vanish" (the original problem)
  • Sometimes it hangs and thus slows down the whole system

The alternatives

In D-INFK department in the ETH we're heavily dependent on the LDAP database, as most services are using it as its primary database. To overcome the problem, there are several solutions:

  • Dump the ldap database into standard /etc/passwd and /etc/shadow
  • Shutdown nscd and let the LDAP-Server handle the load
  • Install unscd

I'm going for the last one now.