[PLUG] centos/rhel 7 ttyUSB group ownership with FTDI adapter

[Johnathan Mantey]

You may want to add something like this to a udev rule:

KERNEL=="ttyUSB[0-9]*",GROUP="dialout",MODE="0660"

You may also like to do something like this (probably won't work for FTDI
knockoffs):
SUBSYSTEM=="tty", ENV{ID_SERIAL}=="FTDI_TTL232R-3V3_FTF89IVR",
SYMLINK+="myCoolUSBDevName"

You can add yourself to the "dialout" group in /etc/groups.  Logout, and
login, and check your group access via 'id'.

Use 'udevadm' magic to get the FTDI serial string.  I leave that research
to your favorite search engine.

Once all of this is done you can use '/dev/myCoolUSBDevName' to refer to
the USB device.

On Wed, Nov 28, 2018 at 3:45 PM Ben Koenig <techkoenig at gmail.com> wrote:

> Even if you removed your custom rules, there might still be a default rule
> that triggers for that device.
> Maybe try searching through the config files in rules.d for the
> vendor:product IDs of that particular adapter.
>
> On Mon, Nov 26, 2018 at 2:32 PM Galen Seitz <galens at seitzassoc.com> wrote:
>
> > Hi,
> >
> > When I connect a Prolific-based USB serial adapter to my CentOS 7
> > machine, the corresponding ttyUSB device has dialout group ownership.
> >
> > [root at toto ~]# ls -l /dev/ttyUSB*
> > crw-rw----. 1 root dialout 188, 0 Nov 26 14:15 /dev/ttyUSB0
> >
> > However, when I connect an FTDI-based serial adapter, the device has
> > root group ownership.
> >
> > [root at toto ~]# ls -l /dev/ttyUSB*
> > crw-rw----. 1 root dialout 188, 0 Nov 26 14:15 /dev/ttyUSB0
> > crw-rw----+ 1 root root    188, 1 Nov 26 14:16 /dev/ttyUSB1
> >
> > Note the trailing '+' on the permissions.  It appears something is
> > setting up an ACL, but only for the FTDI.
> >
> > [root at toto ~]# getfacl /dev/ttyUSB1
> > getfacl: Removing leading '/' from absolute path names
> > # file: dev/ttyUSB1
> > # owner: root
> > # group: root
> > user::rw-
> > user:galens:rw-
> > group::rw-
> > mask::rw-
> > other::---
> >
> > The ACL suggests that I should have rw access, but kermit can't open the
> > port.
> >
> > Note that I removed all of my custom udev rules and ran udevadm control
> > --reload-rules before performing this test.
> >
> > I can sudo to workaround the problem, but I shouldn't have to.  Any
> > ideas as to what is going on?
> >
> >
> > thanks,
> > galen
> > --
> > Galen Seitz
> > galens at seitzassoc.com
> > _______________________________________________
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> >
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