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

[Galen Seitz]

Hi,

When I connect a Prolific-based USB serial adapter to my CentOS 7
machine, the corresponding ttyUSB device has dialout group ownership.

[***@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.

[***@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.

[***@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

[Ben Koenig]

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.

Post by Galen Seitz
Hi,
When I connect a Prolific-based USB serial adapter to my CentOS 7
machine, the corresponding ttyUSB device has dialout group ownership.
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.
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.
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
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