i have a dilemma. I have live rhel system running which I can login through after enabling serial console redirection.
basically root + password.

however i am automating the login process using pythin pexpect interactive module which can emulate the login process. it essentially works except the login is always denied. I double checked everything in the code and can find any fault, it always sends the username when prompted and sends correct password when prompted.

that means i need to do some debugging. is there any way i can sniff the value of password being received from the linux side? as always the login is over the ssh protocol?

as i said the serial console redirection is done through ssh connection that redirects the whole display terminal not just linux and the automation module uses this out-of-band terminal to interact with the linux.

so I can not use this terminal to do debugging. if i manage to login through host os IP and do some sniffing, what options available? Thanks.,

Creds sniffing is frowned upon (for good reason) and a questionable tactic if you have not exhausted your other options. On top of that root logins are (rightfully so) subject to restrictions and its not clear from your case (not having seen you check system configs, securetty, PAM, system logs etc, etc) if that's what's blocking what you try to do. I strongly suggest you first test your process with an unprivileged user account to be able to validate the login process, run your code in debug mode and post code snippets / output to support your case.

Going SSH why not use key login instead of password?

i figured out thanks.
i was sending password and ENTER char in a separate line. That obviously introduced some char in between. I had to send password+enter char in one line.