ttys -- System Administration

Describe terminal ports
/etc/ttys

File /etc/ttys describes the terminals in the COHERENT system.  The process
init reads this file when it brings up the system in multi-user mode.

/etc/ttys contains  one line for each terminal.  Each  line consists of the
following four fields:

1. The first  field is one character  long, and indicates if  the device is
   enabled for  logins: `0' indicates  that the device is  not enabled, and
   `1' (one) indicates that logins are enabled for the device.

2. The second field is one character long, and indicates whether the device
   is local  (i.e., a  terminal) or remote  (i.e., a modem):  `r' indicates
   remote, and `l' (lower-case L) indicates local.

   If the port is named in file /etc/dialups, then the command login checks
   the file  /etc/d_passwd to see  if the program  the user is  invoking is
   protected by a password.  If so, it prompts the user for that additional
   password before  allowing her to  log in.  For details,  see the Lexicon
   entries for login, dialups, and d_passwd.

3. The third  field is one character  long, and sets the  baud rate for the
   device.  Note  that a  device can  have either a  fixed baud rate,  or a
   variable baud rate.  The following  table gives the codes for fixed baud
   rates:

   C      110
   G      300
   I     1200
   L     2400
   N     4800
   P     9600
   Q    19200
   S    38400

   The common variable-speed codes terminal types are as follows:

   0   300, 1200, 150, 110
   3   2400, 1200, 300

   When a user  dials into a variable-speed line, a  message is sent to the
   terminal   using  the   first   speed  listed.    If   the  message   is
   unintelligible, the user hits the <break> key and the system tries
   the next speed; and so on, until the correct speed is selected.

4. The fourth field  names the port that this device  is plugged into.  The
   following table names the ports that COHERENT recognizes:

   console      The console device
   colorN       Virtual console device N, color console
   monoN        Virtual console device N, monochrome console
   comNl        Serial port comN, local device
   comNr        Serial port comN, remote device
   comNfl       Serial port comN, local device, flow control
   comNfr       Serial port comN, remote device, flow control
   comNpl       Serial port comN, local polled device
   comNpr       Serial port comN, remote polled device

   Note that if field 2 (described above) says that this is a local device,
   then you must use a port descriptor that ends in `l'; likewise, if field
   2 states that  this is a remote device, the  port descriptor must end in
   `r'.  Doing otherwise will result in trouble.  See Lexicon entry asy for
   details.   Note also  that  you must  use  a device  with hardware  flow
   control (i.e.,  a device  whose suffix includes  the letter `f')  if you
   wish to use a high-speed modem (e.g., 14.4bis).

Do not leave  trailing spaces at the end of  an entry in /etc/ttys. Leaving
blanks at  the end of  a line usually  results in errors that  state that a
device could not be found.

After you  have edited /etc/ttys, the following  command forces COHERENT to
re-read the file and use the new descriptions:

    kill quit 1

Examples

Consider the following ttys entry:

    1lPconsole

Field  1 is  the  first character.   Here  it is  set to  `1' (one),  which
indicates that  the device is  enabled for logins.   Field 2 is  the second
character.  Here it is set to `l' (lower-case L), which indicates that this
is a  local device.  Field  3 is the  third character.  Here, it  is set to
`P', which  indicates that the  device operates at  the fixed baud  rate of
9600 baud.   This field is ignored  by the console device  driver since the
console is not  a serial device.  Finally, field 4  is the remainder of the
line.  Here, it indicates that the device in question is the console.

Now, consider another example:

    1r3com3r

Field  1 is  the  first character.   Here  it is  set to  `1' (one),  which
indicates that  the device is  enabled for logins.   Field 2 is  the second
character.  Here  it is set to  `r', which indicates that  this is a remote
device, i.e., a modem.  Field 3 is the third character.  Here, it is set to
`3', which  indicates that  the device operates  at variable baud  rates of
2400, 1200, and 300.  By hitting the <break> key on the terminal, the
user can select from among those three baud rates, in that order.  Finally,
field 4 is  the remainder of the line.  Here,  it indicates that the device
in question  is plugged into  port com3, and  is accessed via  special file
/dev/com3r.

Files

/etc/ttys

See Also

Administering COHERENT,
asy,
d_passwd,
dialups,
getty,
init,
login,
stty,
terminal,
tty

Notes

If  you wish  to enable  logins on  a COM  port on which  you will  also be
dialing  out, you  must edit  file  /etc/ttys and  add a  line for  the raw
device.  For example, if you have a modem plugged into COM1 and you wish to
dial out  on that port,  you must have  an entry for both  com1l and com1r.
Note that the  entry for com1r must precede the  entry for com1l. If you do
not do  this, the commands cu  and uucico cannot disable  com1r before they
dial out on com1l.

cu  also  requires  that  the  device  /dev/console  appear  last  in  file
/etc/ttys. If  this is not  so, cu refuses  to disable the  enabled port or
dial out.

© 2012 by Stephen A. Ness