Friday, July 18, 2008

What is Pseudo Terminal (PTY)?

Honestly, I did not know about the Pseudo Terminal before facing a problem. I had overwritten /etc/fstab in Fedora 8. As a result, I was not able to open either Terminal or Konsole. The error, I was getting, was:

Not enough permission for PTY device.

Then, I searched Internet for PTY device, there I found the full form of PTY, which is Pseudo Terminal.

Like the /dev directory, /dev/pts contains entries corresponding to devices. But unlike /dev, which is an ordinary directory, /dev/pts is a special directory that is created dynamically by the Linux kernel.The contents of the directory vary with time and reflect the state of the running system.

The entries in /dev/pts correspond to pseudo-terminals (or pseudo-TTYs, or PTYs). Linux creates a PTY for every new terminal window you open and displays a corresponding entry in /dev/pts.The PTY device acts like a terminal device—it accepts input from the keyboard and displays text output from the programs that run in it. PTYs are numbered, and the PTY number is the name of the corresponding entry in /dev/pts.

Then, I searched for how to open Pseudo Terminal with enough permissions.

Solution: Since I had overwritten the /etc/fstab, the entry to

mount devpts was not present. I then created the following entry in /etc/fstab file.

# file_system mount_point type options dump pass

none /dev/pts devpts (rw,mode=620) 0 0

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