1Each mount of the devpts filesystem is now distinct such that ptys
   2and their indicies allocated in one mount are independent from ptys
   3and their indicies in all other mounts.
   5All mounts of the devpts filesystem now create a /dev/pts/ptmx node
   6with permissions 0000.
   8To retain backwards compatibility the a ptmx device node (aka any node
   9created with "mknod name c 5 2") when opened will look for an instance
  10of devpts under the name "pts" in the same directory as the ptmx device
  13As an option instead of placing a /dev/ptmx device node at /dev/ptmx
  14it is possible to place a symlink to /dev/pts/ptmx at /dev/ptmx or
  15to bind mount /dev/ptx/ptmx to /dev/ptmx.  If you opt for using
  16the devpts filesystem in this manner devpts should be mounted with
  17the ptmxmode=0666, or chmod 0666 /dev/pts/ptmx should be called.
  19Total count of pty pairs in all instances is limited by sysctls:
  20kernel.pty.max = 4096           - global limit
  21kernel.pty.reserve = 1024       - reserved for filesystems mounted from the initial mount namespace                   - current count of ptys
  24Per-instance limit could be set by adding mount option "max=<count>".
  25This feature was added in kernel 3.4 together with sysctl kernel.pty.reserve.
  26In kernels older than 3.4 sysctl kernel.pty.max works as per-instance limit.
  27 kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.