SUMMARY: Re: Q. Relation btwn pts, pty and tty?

From: Stephanie Lam (MIS) (
Date: Mon Aug 09 1999 - 12:26:56 CDT


Thanks for the replies from Casper, Sean, Robert and Nickolai. Appreciate

Found other info from various docs:

To find out how many ptys are being used:

root@abba >crash
dumpfile = /dev/mem, namelist = /dev/ksyms, outfile = stdout
> pty
ptms_tty TABLE SIZE = 48
   0 605d7dd8 60536a70 604e9248 103 mopen sopen
   1 60630b78 60630988 604e8e88 465 mopen sopen
   2 60655a08 60655818 604e88e8 103 mopen sopen
   3 60654898 606546a8 6067c348 103 mopen sopen

To find out what processes are using the pts:
fuser /dev/pts/*

To extend the number of ptys allowed:
increase "pt_cnt" in /etc/system and "boot -r".

I think pty and pts are the same (based on the replies). Tty is the terminal

I am still a little uncertain about the relationships among them - how they
relate to each other but I will keep on looking.

Thanks for your time!

- Stephanie

>What is the relation among pts, pty and tty? How many pts,pty,tty does a
>user take up when he/she telnets/logins into a system?

He will use one /dev/pts/* entry for each telnet, one for each login and
one for each xterm/dtterm window.

To get more ptys, increase "pt_cnt" in /etc/system and "boot -r".

(You cannot change them on the fly an dyou do not have to change anything
but pt_cnt)

First, telnet requires 1 pts per telnet. rlogin requires 2 pts' per

pts=pseudo terminal (alt login/window device). Solaris gives 48 by
default. When they're all in use, no more logins or windows allowed.
pty=same BSD-style
tty=terminal type (aka teletype), also, a command that returns the terminal
name (eg: /dev/pts/4).

Hope this helps.

Sean Quaint, CSA, CSNA
A tty is a physical serial connection.
On the back of your machine, you'll see
two 25 pin rs232 connections labelled
ttya and ttyb. You can add physical tty's
with specilized hardware.

pttys are "psuedo" tty's, created by telnet
sessions. there is a limit to the number
of pttys' that a system will support. That
limit is controlled out of /etc/system.

Metcalf, Robert
I _think_ in most configurations users just use one pts.


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