SSH_Getting do_exec_no_pty error !

[Bala_Unix]

Team

We are getting this error do_exec_no_pty: command = date  while  establishing concurrent ssh connections from Linux to HP-UX . Initiated 30 concurrent sessions but established only 19 connections and 11 connections were failed with this error code error do_exec_no_pty: command = *** 

This is FYI

- Linux OS info - RHEL 7.3

- HPUX : 11.31

- Password less ssh configured between these hosts

Please help me on this case .

Thanks

Bala.

[Bill Hassell]

There are two places to adjust the maximum number of pty device files that can be used.

First, check the two kernel parameters nstrpty and npty.

# kctune npty nstrtel nstrpty
Tunable Value Expression
npty 60 Default
nstrpty 60 Default
nstrtel 60 Default

These should be much larger than you will need in the future. 
Set them all to 200, or more if you'll need more simultaneous connections in the future.
You can set all 3 on one line.
But it does require a reboot to complete the change.

# kctune -h npty=200 nstrtel=200 nstrpty=200
     ==> Update the automatic 'backup' configuration first? y
       * The automatic 'backup' configuration has been updated.
       * Future operations will update the backup without prompting.
       * The requested changes have been saved, and will take effect at
         next boot.
Tunable               Value  Expression
npty     (now)           60  Default
         (next boot)    200  200
nstrpty  (now)           60  Default
         (next boot)    200  200
nstrtel  (now)           60  Default
         (next boot)    200  200

After rebooting, you need to create the additional device files
Use insf to add the device files.

# insf -d pts -s 200

This will create the needed ptys device files for SSH.

[RajUX]

It is possible that some of the pty devices are not released by some processes.

Increasing the terminal devices as suggested by Bill would be a possible workaround.

You could contact HPE if the workaround does not help and if you need more troubleshooting of the issue.

[Bala_Unix]

Thanks for your time and input on this case Bill .

Yes, we have increased these npty nstrtel nstrpty value  to 2000 and after reboot additional pty device also added  .

But , Still no luck . Getting same error 

This is FYI

# kctune npty nstrtel nstrpty
Tunable Value Expression
npty 2000 2000
nstrpty 2000 2000
nstrtel 2000 2000