I can't create a character device inside of /dev/pts/ even as root

Question

sudo mknod /dev/pts/mytty c 0 9

mknod: /dev/pts/mytty: Operation not permitted

How come I cannot create a character device file in this directory?

The filesystem (devpts) doesn't support creating any files. Even if you're root, you can't do something that's impossible. Theoretically, it would be possible to overlay-mount that directory with another dir from a fs where you can create files, but that will break /dev/ptmx and any programs which create pseudo-ttys (screen, xterm, ssh, etc) — user313992
– user313992, Commented Dec 6, 2021 at 6:56
if programmatically, there's an example in the manual gnu.org/software/libc/manual/html_node/Allocation.html — jyz
– jyz, Commented Jan 11, 2024 at 16:30

jyz · Accepted Answer · 2024-01-11 16:20:39Z

You can create a pseudo-terminal programmatically or using (already created) tools. As an example, here you create /tmp/mypty using socat:

socat pty,link=/tmp/mypty,waitslave -

Then you can read from / write to this file.

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