SUMMARY: telnetd: open /dev/ptmx: No such device

From: Antonio Figueiredo (
Date: Thu Jul 02 1998 - 07:51:16 CDT

The original question was:

>Has anyone faced this problem, when I either telnet or
>rlogin to the machine "A" the following message appears.
>% telnet A
>Connected to
>Escape character is '^]'.
>telnetd: open /dev/ptmx: No such device
>Connection closed by foreign host.

Thanks to:
 Casper Dik
 Alfredo de Luca KELEMEN Peter Wim Olivier Amjad Zamil
 Vipin Gupta PITCHUMANI G Brett Lymn Bismark Espinoza
 Ginny Bolyard Benjamin Cline Tim Carlson Tunde.Adeyeri
 Oliver Hemming Aaron Lineberger Mike D. Kail Craig Gates

The answer is:

The solaris FAQ says:

3.40) How can I have more than 48 pseudo-ttys?

    Edit /etc/system and add the following line:

        * System V pseudo terminals

        set pt_cnt = <num>

    Halt the system and boot -r.

    You can essentially have as many as you like, but you'll probably
    run into some other limit somewhere. More than 3000 are supported.

    In the unlikely event that you run out of BSD-style ptys,
    you can increase them as well. The maximum here is currently
    176 for pty[p-z][0-9a-f]. This is somewhat less that the BSD
    maximum of 256 limited by 8 bit device minor numbers.

    BSD ttys are awkward to use and all programs I found support SYSV
    ptys without trouble.

        * You don't need this. Increasing this value too much usually
        * just wastes memory.
        * BSD application never support more than 256 ptys.
        * Solaris 2.x supports no more that 176 BSD ptys.

        set npty = <num>

    But you're not there yet, you also need to edit /etc/iu.ap and
    substitute the new value of "npty-1" for the "47" on the following
    line, in case you do increase the number of BSD style ptys.

                ptsl 0 47 ldterm ttcompat

    Halt the system and boot -r.

5.28) I get /dev/ptmx: No such device when attempting to telnet/rlogin in.

    You need to increase the number of pseudo ttys (See 3.40).

    --- end of excerpt from the FAQ

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Antonio Figueiredo
Computer Engineering & Ind. Automation
School of Electrical & Computer Engineering
State University of Campinas - Campinas, SP BRAZIL +55 19 788-3845
"UNIX *is* user-friendly. It's just selective about who its friends are."

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