Solving 'too many open files' problem on NetBSD

When you see 'too many open files' message in the log of any userspace program, you have to tweak a couple of things to eliminate.

1. Check how many files are open parallel

$ fstat | wc -l

2. Check what is the limitation of the user

$ ulimit -n

3. Check what parameters have the system as soft and hard limits

# sysctl | grep kern.maxfiles
# sysctl | grep proc.curproc.rlimit.descriptors.hard
# sysctl | grep proc.curproc.rlimit.descriptors.soft

4. Set those sysctl parameters according to your needs

# sysctl -w kern.maxfiles=65535
# sysctl -w proc.curproc.rlimit.descriptors.hard=unlimited
# sysctl -w proc.curproc.rlimit.descriptors.soft=13196

The above example assumes that you would not exceed 13196 open files/process. If you need more, just try. If everything works well, write your own values into /etc/sysctl.conf.  

5. Set the ulimit for the user

Edit the file /etc/login.conf after reading how to. Set openfiles-cur to your soft sysctl limit.
Restart the system, and check  all parameters as described in 2^nd and 3^rd section. If parameters are ok, try your program again. If not, read on, because your kernel limits the resources.

6. Build a new kernel

Read how to build a kernel for NetBSD. See the attached link. Set the parameter maxusers higher then the current (GENERIC kernel is set up to 64). I have tried with 256, the config script warned, but compilation and run of the new kernel was perfect, so it's up to you.

After building a good working new kernel you should be able to hack parameters as described in 4. 5. sections.

Good luck!