npty.5 (2010 09)

n
npty(5) npty(5)
(Tunable Kernel Parameters)
NAME
npty - maximum number of BSD pseudo terminals (ptys)
VALUES
Default
npty =
60
Allowed Values
Minimum : 1
Maximum : System memory size
DESCRIPTION
npty is the number of pseudo terminal (pty) drivers that a system can support. The pty driver provides
support for a device-pair called a pseudo terminal. A pseudo terminal is a pair of character devices, a
master device, and a slave device. These allow communication between an application process and a
server process. When sending data to pty devices (such as windows), a pty device must exist for every
window that is open at any given time.
Using a parameter value significantly larger than the number of ptys is not recommended. An exces-
sively large value wastes kernel memory space.
Who Is Expected to Change This Tunable?
Users with the SYSATTR privilege. See privileges (5) for more information about privileged access on sys-
tems that support fine-grained privileges.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
This tunable value needs to be raised when the system runs out of ptys.
What Are the Side Effects of Raising the Value?
More system memory is used.
When Should the Value of This Tunable Be Lowered?
This value should be lowered when a minimal system is being created.
What Are the Side Effects of Lowering the Value?
The system may run out of ptys.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at
http://www.hp.com/go/hpux-core-docs
.
AUTHOR
npty was developed by HP.
SEE ALSO
kctune(1M), privileges(5), pty(7).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1