Limits on open filehandles

• Any Unix: the limits set by ulimit or setrlimit.
• FreeBSD:
  Edit /boot/loader.conf, add the line

  set kern.maxfiles=XXXX

  where XXXX is the desired system limit on file descriptors, and reboot. Thanks to an anonymous reader, who wrote in to say he'd achieved far more than 10000 connections on FreeBSD 4.3, and says

  "FWIW: You can't actually tune the maximum number of connections in FreeBSD trivially, via sysctl.... You have to do it in the /boot/loader.conf file.
  The reason for this is that the zalloci() calls for initializing the sockets and tcpcb structures zones occurs very early in system startup, in order that the zone be both type stable and that it be swappable.
  You will also need to set the number of mbufs much higher, since you will (on an unmodified kernel) chew up one mbuf per connection for tcptempl structures, which are used to implement keepalive."

  
  
• Linux: See Bodo Bauer's /proc documentation. On 2.4 kernels:

  echo 32768 > /proc/sys/fs/file-max

  increases the system limit on open files, and

  ulimit -n 32768

  increases the current process' limit.

  On 2.2.x kernels,

  echo 32768 > /proc/sys/fs/file-maxecho 65536 > /proc/sys/fs/inode-max

  increases the system limit on open files, and

  ulimit -n 32768

  increases the current process' limit.