[ale] help please getting script file to work

[Ron Frazier (ALE)]

Hi Andrew and others,

Thanks for the replies on this thread.  I actually have my script mostly 
working now in the incarnation directly below when I double click it 
from the desktop.  I haven't gotten around to trying to auto boot it 
yet.  I could have posted this question on the NTP questions list at 
ntp.org, however it was more of a Linux specific thing so I posted it 
here.  I've been throwing a bunch of other questions at them anyway.

Two things were keeping my script from not working at all, which are now 
fixed:

The absence of this line: #!/bin/bash, which I'll probably change to 
#!/bin/sh - as Mike W. suggested.  I have no idea what this does!  Looks 
like a comment to me.

Also, I had quotes around all the commands, which the system didn't like.

I posted a thread with this subject yesterday: "how I did Ubuntu + NTPD 
+ GPS, but how do I keep it?"  All of my saga is described there.  In 
answer to your question, my GPS is a GlobalSat BU-353 and I'm running 
Ubuntu 11.04.

Like I said, the script is essentially working.  It's whole purpose is 
to stop NTPD, initialize the USB com port for the GPS, then restart 
NTPD.  I know that the GPS works once that's done.

Right now, I'm having a problem that's driving me insane.  Here's an 
NTPQ printout before running my script.  Notice that the computer is 
synchronized closely to the time servers and there is no GPS.  The top 
server is the current clock.

ron at asus-k52f-1:/etc$ ntpq -p
      remote           refid      st t when poll reach   delay   offset  
jitter
==============================================================================
*nist1-ny.ustimi .ACTS.           1 u  118  128  377   54.015   -3.923  
10.731
-216.119.63.113  .ACTS.           1 u   63  128  377   55.535   12.876   
3.762
+india.colorado. .ACTS.           1 u   61  128  377   60.914   -7.932   
2.995
+ping-audit-207- .ACTS.           1 u  126  128  277   84.008   -6.617   
5.344

Then, I run the script.  Here is the NTPQ printout shortly after running 
the script:

ron at asus-k52f-1:/etc$ ntpq -p
      remote           refid      st t when poll reach   delay   offset  
jitter
==============================================================================
*GPS_NMEA(5)     .GPS1.           0 l    3    8  377    0.000  595.804  
88.950
  nist1-ny.ustimi .ACTS.           1 u    8   64    7   55.065  570.579  
52.070
  216.119.63.113  .ACTS.           1 u    6   64    7   55.089  594.824  
44.885
  india.colorado. .ACTS.           1 u    7   64    7   60.848  633.795  
63.543
  ping-audit-207- .ACTS.           1 u   10   64    7   85.777  576.470  
45.730

Now, the GPS has appeared, so I know the USB com port is working.  
However, now my clock is ~ 500 ms off from ALL the servers including the 
GPS.  I have the time coming from the GPS fudged so it closely matches 
the NIST servers.  So, I don't really think this is related to the GPS, 
per se, but NTPD is going bonkers or NTPQ is going bonkers.  All I know 
is I'm going bonkers and I cannot figure out where this instant offset 
is coming from.

On Windows, using a recent version of the Windows port of NTPD from Dave 
Hart's website, I can stop the service with it closely synchronized with 
either the GPS or the internet servers, tinker with the configuration, 
and restart NTPD and it picks up right where it left off, with almost no 
additional offset at all.  I MAY have seen it do this once or twice in 
Windows, but I can't remember for sure.  The restart sequence at the 
bottom of my script is supposed to clear up the problem, and that seems 
to work sometimes when I do it manually.

I don't know what's going on here.  Anybody have any clues?  Thanks for 
all the help.

By the way, I'd also like to know how to make my script print things on 
the screen as it progresses through.  In DOS, I'd use ECHO, but I don't 
know the command here.

Sincerely,

Ron


---------------------------

Current version of my script file.

#!/bin/bash

# script file to stop ntpd, initialize the usb gps, then restart ntpd
# Ron Frazier - 2012-02-15

# stop ntpd
sudo /etc/init.d/ntp stop

# set up the com port
log_daemon_msg "Setting /dev/ttyUSB0 comm parameters."
sudo stty -F /dev/ttyUSB0 57600 igncr clocal -echo -ixon

# set up link to /dev/gps5
log_daemon_msg "Creating link to /dev/gps5."
sudo ln -T /dev/ttyUSB0 /dev/gps5

# set the clock
sudo ntpdate -b nist1-ny.ustiming.org

# start ntpd
sudo /etc/init.d/ntp start

# wait 5 seconds
sleep 5

# ---- cycle ntpd again

# stop and restart ntpd
sudo /etc/init.d/ntp restart

# wait 5 seconds
sleep 5



On 02/15/2012 07:43 PM, Andrew Wade wrote:
> Can you tell us the model of the USB GPS device?  I see some other 
> posts about that same command:  stty -F /dev/ttyUSB0 57600 igncr 
> clocal -echo -ixon
>
> I want to understand which commands you are using are working or not 
> (or if you just grabbed them from another source and tried to do the 
> same thing in a different Linux OS with no luck)
>
> Also, what Linux are you using?
>
> On Wed, Feb 15, 2012 at 5:08 PM, Michael H. Warfield <mhw at wittsend.com 
> <mailto:mhw at wittsend.com>> wrote:
>
>     On Wed, 2012-02-15 at 14:24 -0500, Jim Kinney wrote:
>     > add a line at the very beginning of the file as below:
>
>     > #!/bin/bash
>
>     #!/bin/sh -
>
>     If you're not specifically using incompatible bashisms, go with
>     /bin/sh
>     (which is bash anyways) just as a matter of good practice.  Ends up
>     doing the same thing, just better practice.
>
>     The following dash ('-') is not NEARLY as important on Linux
>     systems as
>     it is on other flavors of *NIX because SUID scripts are not
>     allowed, but
>     it's generally a good idea (BCP) to include that '-' and is
>     generally a
>     standard practice in most "sh/bash/as/ksh" scripts.  There use to be
>     some old security vulnerabilities on SunOS with SUID scripts where the
>     '-' was not included, which is where that practice originated.
>
>     > better choice to have it start automagically is to write a
>     script modeled
>     > after the ones in /etc/init.d to set up the gps modem and have
>     that process
>     > run before the ntpd is started.
>
>     Concur.  Create yourself a nice gps-setup script and link it to
>     99-gps-setup to take care of those things.  Pouring it into
>     rc.local is
>     an option but not nearly as elegant.
>
>     Mike
>


-- 

(PS - If you email me and don't get a quick response, you might want to
call on the phone.  I get about 300 emails per day from alternate energy
mailing lists and such.  I don't always see new messages very quickly.)

Ron Frazier

770-205-9422 (O)   Leave a message.
linuxdude AT c3energy.com

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