[lug] ssh login error

D. Stimits stimits at comcast.net
Tue Jan 9 20:25:08 MST 2007

Lee Woodworth wrote:

> D. Stimits wrote:
>> Steve Webb wrote:
>>> I had a similar experience on a hosted server (vmware-type 
>>> situation) where they limited the number of PTYs that I had (I was 
>>> running GNU 'screen' and ran out of PTYs pretty quickly).  I asked 
>>> the hosting company to adjust the number of PTYs so I could spawn 
>>> more 'screen' sessions and it kind of went away.
>> Everything seems to center on this, but I know the CentOS kernel is 
>> not a dumbed-down kernel, so I can't imagine I have to recompile for 
>> pty's. 
> The kernel has an option for legacy unix ptys (probably not the exact 
> name).
> This enables /dev/ptys. It doesn't have to be enabled. I don't have any
> /dev/ptys on my systems, they use the newer device names and the 
> devpts file
> system.
> Check for the character device /dev/ptmx (c 5 2) root, root 0666
> and the /dev/pts dir. These are signs you have the newer pseudo
> terminal setup. Also a plain mount command would show this line:
>    devpts on /dev/pts type devpts (rw)
> The newer setup creates the /dev/pts/<n> dir entries as needed.
> They will have the ownership of the login using the pty.
This indicates the system is entirely non-legacy via the ptmx and 
/dev/pts/<number>. Why it would fail to be able to get a pty is a 
mystery, the /dev/pts/ only has a couple of entries when it fails...and 
of course sometimes it works and has a couple dozen entries.

> Don't know why you are having issues. There are consoles, virtual 
> terminals, and
> pseudo terminals that one can use for login. I think gettys manage the
> console and the virtual terminals ctl-alt-fn<1....7>. Net daemons like
> ssh use pseudo terminals for the I/O.

Is there some sort of adjustable limit like accounting that would cause 
it to not produce more pty's in /dev/pts/ when there are only 2 or 3 there?

D. Stimits, stimits AT comcast DOT net

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