serial port (USB) permissions

[Johan Helsingius]

Hi,

Connecting a serial adapter to the USB port works otherwise
OK (shows up as /dev/ttyU0, but seems only root has access
to the port. I am used to some group like "dialout" having
access as well. Is there some setting for allowing ordinary
users access. or do I have to do a chmod every time I connect
the device?

Julf

[Marco Moock]

ls -la /dev/ttyU0

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Gruß
Marco

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[Johan Helsingius]

On 06/08/2025 17:02, Marco Moock wrote:
> ls -la /dev/ttyU0

crw------- 1 root wheel 0x19f Aug 6 16:24 /dev/ttyU0

(before I did chmod a+rx to get things to work)

Julf

[Arthur Chance]

Take a look at man devfs.rules (and maybe man devfs).

You want a local ruleset and a rule something like

add path /dev/ttyU* mode 0660 group dialer

You'll also need to set devfs_system_ruleset in /etc/rc.local to use the
new local ruleset.

--
We should have listened when the modems screamed at us.

[Carl Johnson]

Look at 'man devfs.conf'. It has similar examples that show how to
automate that. I have the following in my /etc/devfs.conf:
own ttyU0 root:dialer
perm ttyU0 660
I also have my user ID in the dialer group in /etc/group.

--
Carl Johnson ca...@peak.org

[Johan Helsingius]

On 06/08/2025 23:38, Carl Johnson wrote:
> Look at 'man devfs.conf'. It has similar examples that show how to
> automate that. I have the following in my /etc/devfs.conf:
> own ttyU0 root:dialer
> perm ttyU0 660
> I also have my user ID in the dialer group in /etc/group.

Great! Thanks!

Julf

[Arthur Chance]

devfs.conf only works for devices that are already attached at boot
time. The OP specifically talked about plugging in a USB adapter which
could happen after boot, which is what devfs.rules is for.

[Johan Helsingius]

On 07/08/2025 08:41, Arthur Chance wrote:
> devfs.conf only works for devices that are already attached at boot
> time. The OP specifically talked about plugging in a USB adapter which
> could happen after boot, which is what devfs.rules is for.

Thanks for the clarification/explanation!

Julf

[Tomek CEDRO]

***/etc/devfs.rules:
[localrules=10]
add path 'ugen*' mode 0660 group operator
add path 'usb/*' mode 0660 group operator
add path 'usb' mode 0770 group operator

***/etc/rc.conf:
devfs_system_ruleset="localrules"

+ add your user to the operator group or change the group name above
to match your needs :-)

+ # service devfs restart

all shoud work now as expected :-)

--
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info

[Johan Helsingius]

Thanks!

Julf