Creating pty device files

[Rumen Ginev]

Hi!
When someone tries to telnet to the system (K260/HP-UX10.20) conection is
closed immediately. The message in syslog is:
telnetd[13420]: Cannot allocate pty
The kernel parameters related to ptys I found are:
npty - 800
nstrpty - 60
nclist - 12900
I think the problem is there are not enough pty (slave/master) device files.
If this is the problem, how to create more pty device files?

Thanks in advance,
Rumen

[Alex Glennie · Accepted solution]

i'd try increasing nstrpy value first ...
to increase the ptys :

insf -d pty0 -n 200
insf -d pty1 -n 200 etc ...

[Bruce Regittko_1]

Hi,

nstrpty is probably the culprit. This sets the maximum number of streams based PTYs allowed on the system. Use sam to change this configurable kernel parameter.

More information can be found at http://docs.hp.com/hpux/onlinedocs/os/KCparams.OverviewAll.html.

--Bruce

[Rumen Ginev]

Tanks again!

I increased pty device files by:

insf -d ptym -n 150
insf -d ptys -n 150

where ptym and ptys are kernel drivers (from lsdev). Now I have 150 device files under /dev/ptym/ and /dev/pty/ for master and slave parts of a pty respectively.

nstrpty kernel parameter is related to the number of device files under /dev/pts/, so I did not change it.

I do not know why, but this solved the problem.

Could someone send links to documents that clarify the things about the pseudo teminals and how telnetd works with them?

Rumen

[Bruce Regittko_1]

Hi again,

Sorry - I was thinking of dtterm, which uses pts device files.

For more information, check the man pages for pts(7), pty(7), and ptm(7).

--Bruce

[James R. Ferguson]

Hi Rumen:

Document #KBRC00000945 should help you. In part:

PTYs are used to open telnet sessions. On 10.x systems they use PTYs(pseudo-terminal) and 11.x systems use PTYs that are pseudo-terminal and Streams-Based.

To check the number of telnet sessions you have available, on the box refusing the connection do:

ls /dev/pty | wc -w
ls /dev/ptym | wc -w

To increase your telnet sessions, increase 'npty'.

1. Use SAM -> Kernel -> Configurable Parameters

npty (10.20 and 11.0)
nstrpty (11.0 only)

Set NPTY and NSTRPTY to 512 where NPTY and NSTRPTY are the desired number of telnet sessions.

2. Rebuild the special device files as follows:

# insf -d ptys -n 512

...(10.20 and 11.0).

# insf -d ptym -n 512
...(10.20 and 11.0)

# insf -d pts -s 512 -e -v
...(for 11.0 only)

...JRF...