Maximum number of legacy PTY in use


Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Maximum number of legacy PTY in use
In linux kernel since version 2.6.12  
The maximum number of legacy PTYs that can be used at any one time.
The default is 256, and should be more than enough. Embedded
systems may want to reduce this to save memory.

When not in use, each legacy PTY occupies 12 bytes on 32-bit
architectures and 24 bytes on 64-bit architectures.