Group of /dev/ttyAMA0

[elektronist]

I want to change the group of /dev/ttyAMA0 from tty to dialout permanently, but couldn't find any entry in udev rules.

Where is the group of /dev/ttyAMA0 defined by udev ? Or any other system...

[jojopi]

The device should be root:dialout unless/until you log in on that terminal, when it is correctly changed to pi:tty. Is that not the behaviour you are seeing, and in what distro image?

[elektronist]

For both graphical and nongraphical pi user:

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pi@raspberrypi ~ $ ls -la /dev/ttyAMA0
crw-rw---- 1 root tty 204, 64 Ara 28 12:59 /dev/ttyAMA0

raspbian wheezy 2012-10-28 fully updated.

So, it looks like with raspbian this device's group is tty not dialout. My goal is to use my serial programs as simple user in dialout group. Of course

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sudo chgrp dialout /dev/ttyAMA0

works. But for a standalone/headless device this is not very practical nor 'nice'.

[elektronist]

Also tried with Bodhi. Result is the same.

With a usb-rs232 dongle:

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pi@raspberrypi ~ $ ls -l /dev/ttyUSB0
crw-rw---T 1 root dialout 188, 0 Dec 29 05:00 /dev/ttyUSB0

[jojopi]

The device should be root:dialout unless/until you log in on that terminal, when it is correctly changed to pi:tty.

Ok, that was misleading. udev sets the device to root:dialout, but getty sets it to root:tty immediately, and login changes it to pi:tty. (There may be some race condition or trigger that can make udev chgrp the device after getty, because I still have some pies where getty is running and the group is dialout.)

Still if you disable getty, which you need to do anyway for most outbound uses of the port, the permissions should stay as you want. Remove or comment out this line from /etc/inittab:

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T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

[elektronist]

The device should be root:dialout unless/until you log in on that terminal, when it is correctly changed to pi:tty.

Ok, that was misleading. udev sets the device to root:dialout, but getty sets it to root:tty immediately, and login changes it to pi:tty. (There may be some race condition or trigger that can make udev chgrp the device after getty, because I still have some pies where getty is running and the group is dialout.)

Still if you disable getty, which you need to do anyway for most outbound uses of the port, the permissions should stay as you want. Remove or comment out this line from /etc/inittab:

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T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

Thanks! That was the solution. Sorry for my belated message.