"cannot set user id: Resource temporarily unavailable" while trying to login or su as a local user.
In CentOS 6, the reason for this error is that the the user’s the number of executing threads has reached the nproc resource limit. You can solve the issues
You can edit /etc/security/limits.d/90-nproc.conf which is
# Default limit for number of user's processes to prevent # accidental fork bombs. # See rhbz #432903 for reasoning. * soft nproc 1024 user1 soft nproc 10240