2

When running who I can see two "sessions" (it is the correct wording ?) from two remote servers:

pts/0
pts/1

I went to /dev/pts and I can see 0 1

Does that mean that I can have two simultaneous remote connections to the Linux host? Is it a similar concept to CISCO's vty lines?

  • A comment about English: “tty's number” = the number of a particular tty (“this terminal is on /dev/pts/3, the tty's number is 3”); “number of ttys” = the total number of ttys (“there are four entries in /dev/pts, the number of ttys is 4”). – Gilles Aug 25 '16 at 22:18
5

Entries are added to /dev/pts dynamically, so you're not limited by the number of entries already present. The kernel uses character devices with majors from 136 to 143 (see devices.txt; thanks to sourcejedi for the pointer!), so you can have up to 2048 entries (256 × (143 ‑ 136 + 1)).

LWN recently published an article on the topic which has a ton of details; you'll also find relevant answers on this site: What is stored in /dev/pts files and can we open them? and What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'? for example.

The underlying concept is known as Unix98 ptys, and appears to be similar to Cisco vtys (from what I've understood of the latter).

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