pseudo terminals: /dev/ptmx and similar

/dev/ptmx <-> /dev/pts/ vs. /dev/ptyp <-> /dev/ttyp

Here it goes:

I remember that quite some time ago I could pair 2 programs like “screen” or “minicom” using /dev/ptyp master and a corresponding /dev/ttyp slave device. These devices are gone for some time now.

Nowadays I think I have to start one of these accessing /dev/ptmx and a slave device is automatically created as /dev/pts/<something>. This auto-create seems to work.

The problem I have is that although I have rw permissions on the devices, no data is going through and I get an error.


  • screen /dev/ptmx
  • /dev/pts/X is created with proper perms
  • screen /dev/pts/X

→ “I/O error, no pty found” or similar.

Help :wink: