Raspberry Pi Forums

Posted: **Mon May 13, 2013 1:34 am**

I need to get this script up and running soon and need a hand.

#! /bin/sh
sudo gpsd /dev/ttyUSB0 -F /var/run/gpsd.sock
sleep 3
gpspipe -r | grep '^\$G' | tee $nmea

that's the script I need run when the machine boots. Any idea?

I keep getting

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May 12 21:21:45 raspberrypi gpsd[322]: gpsd:ERROR: read-only device open failed: Permission denied
May 12 21:21:45 raspberrypi gpsd[322]: gpsd:ERROR: /dev/ttyUSB0: device activation failed.

when I put it in RC.Local

Thanks for the help,
Alfa

Posted: **Mon May 13, 2013 2:27 am**

/dev/ttyUSB0 probably belongs to the "dialout" group or similar.

To confirm this post the output of

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ls -l /dev/ttyUSB0
groups gpsd

Add the gpsd user to this group

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sudo usermod --append --group dialout gpsd

to give it permission to change that device.

Posted: **Mon May 13, 2013 3:45 am**

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pi@raspberrypi ~ $ ls -l /dev/ttyUSB0
crw-rw---T 1 root dialout 188, 0 Dec 31  1969 /dev/ttyUSB0
pi@raspberrypi ~ $ groups gpsd
groups: gpsd: No such user

I'll try that 2nd piece you sent me. Thanks!

Edit:

It looks like it didn't work:

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pi@raspberrypi ~ $ sudo usermod --append --group dialout gpsd
usermod: user 'gpsd' does not exist
pi@raspberrypi ~ $

Posted: **Mon May 13, 2013 5:22 am**

alfa147x wrote:It looks like it didn't work:
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pi@raspberrypi ~ $ sudo usermod --append --group dialout gpsd
usermod: user 'gpsd' does not exist
pi@raspberrypi ~ $ 

I thought GPSD installed a new user (gpsd) which it drops privelege to after starting as root.

is there anything in the log file about changing UID? maybe to "nobody"?

can you add "pi" to the "dialout" group and pass "-u pi" to the gpsd command?
(from memory, don't have gpsd here right now, that should set UID to "pi" which should work)

Posted: **Mon May 13, 2013 1:05 pm**

Thanks for the help!

sprinkmeier wrote:
alfa147x wrote:It looks like it didn't work:
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pi@raspberrypi ~ $ sudo usermod --append --group dialout gpsd
usermod: user 'gpsd' does not exist
pi@raspberrypi ~ $ 
I thought GPSD installed a new user (gpsd) which it drops privelege to after starting as root.

is there anything in the log file about changing UID? maybe to "nobody"?

can you add "pi" to the "dialout" group and pass "-u pi" to the gpsd command?
(from memory, don't have gpsd here right now, that should set UID to "pi" which should work)

Hmm. I'll give that a try. If I reinstall GPSD would it try to create the missing user?

Posted: **Mon May 13, 2013 5:46 pm**

Someone on another forum sent me to this link. I'll be giving it a try tonight as well:
http://unix.stackexchange.com/questions ... tart#25263

Posted: **Mon May 13, 2013 9:10 pm**

alfa147x wrote:Thanks for the help!
Hmm. I'll give that a try. If I reinstall GPSD would it try to create the missing user?

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$ sudo apt-get install gpsd gpsd-clients
$ vi /etc/default/gpsd 
# change START_DAEMON to "true"
$ sudo vi /etc/default/gpsd 
$ sudo /etc/init.d/gpsd start
$ ps auxwww | grep gps
nobody    6796  0.2  0.3   4964  1572 ?        S<s  06:33   0:00 /usr/sbin/gpsd -F /var/run/gpsd.sock -P /var/run/gpsd.pid
pi        6800  0.0  0.1   3544   804 pts/2    S+   06:34   0:00 grep --color=auto gps

Looks like it uses "nobody" on the RasPi. The "gpsd" user might be a mis-remembering on my part or something from an earlier version/different platform.

Read the gpsd man page, esp. "SECURITY AND PERMISSIONS ISSUES".

Try the udev thing, it should work and it's a useful trick to know.

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Need help getting this script to run when the RPi starts.

Need help getting this script to run when the RPi starts.

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Re: Need help getting this script to run when the RPi starts

Re: Need help getting this script to run when the RPi starts

Re: Need help getting this script to run when the RPi starts

Re: Need help getting this script to run when the RPi starts