Ubuntu seems to disable this by default in their packages with the following comment:

```
# netgroup caching is known-broken, so disable it in the default config,
# see: https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/1068889
enable-cache            netgroup        no
```

According to the bug the fix has been released but I still see the above in 13.04s nscd package.