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Full Discussion: kill the tty
Top Forums Shell Programming and Scripting kill the tty Post 49726 by Perderabo on Thursday 8th of April 2004 07:16:06 PM
Old 04-08-2004
Well what's happening there is a daggling utmp entry. How that happened depends on exactly how you logged in. In a typical scenario, telnetd is forked when someone connects via telnet. telnetd forks a login program which makes the utmp entry that you saw. The login program execs a shell. Eventually the shell exits. telnetd is the parent of that shell and notices the death of its child. So it cleans up that utmp entry and exits.

Now, consider what would happen if that telnetd instance was killed with a -9 signal. It dies immediately. It can't clean anything up.

I see you are still going straight for the -9 in your script. You might want to try the advice I gave in that first thread.

With all of this said, the telnetd instance does not normally acquire the terminal as a controlling terminal and so I would not expect this particular script to kill telnetd. And you may not be using telnet anyway. Still, somehow, the parent process of the shell is dying permaturely. And I would tend to suspect your -9 habit as the cause.

Also the contents of the utmp file is not really important. People can connect and not have a utmp entry. And, as you see, utmp can have garbage laying around. ps is the command to use to know what's happening on your system.
 

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telnetd(8c)															       telnetd(8c)

Name
       telnetd - DARPA TELNET protocol server

Syntax
       /etc/telnetd

Description
       The  server  supports the DARPA standard TELNET virtual terminal protocol.  The TELNET server is invoked when receives a connection request
       on the port indicated in the TELNET service description.

       The server operates by allocating a pseudo-terminal device for a client, then creating a login process which has  the  slave  side  of  the
       pseudo-terminal	as stdin, stdout, and stderr.  The server manipulates the master side of the pseudo terminal, implementing the TELNET pro-
       tocol and passing characters between the client and login process.

       When a TELNET session is started up, sends a TELNET option to the client side indicating a willingness to do remote echo of characters,	to
       suppress  go  ahead, and to receive terminal type information from the remote client.  If the remote client is willing, the remote terminal
       type is propagated in the environment of the created login process.  The pseudo terminal allocated to the client is configured  to  operate
       in cooked mode and with XTABS and CRMOD enabled.

       Aside  from  this  initial  setup, the only mode changes will carry out are those required for echoing characters at the client side of the
       connection.

       The server supports binary mode, suppress go ahead, echo, and timing mark.  It also allows a remote client to do binary, terminal type, and
       suppress go ahead.

Restrictions
       Some TELNET commands are only partially implemented.

       The TELNET protocol allows the exchange of the number of lines and columns on the user's terminal, but does not make use of them.

       The terminal type name received from the remote client is converted to lower case.

       The server never sends TELNET go ahead commands.

See Also
       telnet(1c), pty(4), tty(4), services(5), inetd(8c)

																       telnetd(8c)
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