I know Linux supports multiple users being logged in at the same time.But what's the maximum number of users that can be logged into Linux at the same time?I see there are there are 69 tty files (ttyn or ttysn, where n is an integer, such as tty0, tty1, tty2... ) in my /dev directory.  I assume that these files are the shells.  So I am thinking that this Linux system will support only 69 user logged in simultaneously. Is my thinking correct?  If my assumption is wrong, please explain the users limit of Linux, including how it's implemented.Also, how do I access the details of already logged in users?  I know commands w, who, but I am looking for sophisticated tools.
How many users does Linux support being logged in at the same time via SSH?
linux;shell;ssh;login;limit
When logging in using SSH, you use a pseudo-terminal (a pty) allocated to the SSH daemon, not a real one (a tty). Pseudo-terminals are created and destroyed as needed. You can find the number of ptys allowed to be allocated at one time at /proc/sys/kernel/pty/max, and this value can be modified using the kernel.pty.max sysctl variable. Assuming that no other ptys are in use, that would be your limit.w, who, and users are the canonical tools for accessing information about logged in users. last and lastlog also contain historical data.