[CentOS] USB Serial ports (ttyACMn) CentOS 6.7 (64-bit) vs. CentOS 6.7 (64-bit)

Sat Feb 13 15:14:30 UTC 2016
Robert Heller <heller at deepsoft.com>

I sent this out about a week or so ago, but I have heard nothing. I am
*thinking* it is a SELINUX problem, but I cannot figure out what. The SELINUX
settings for both machines are *exactly* the same (the stock defaults for a
standard CentOS 6 install).  The *only* difference is that the desktop 
(sauron) has a few VMs setup (under KVM) and the laptop (gollum) does not. The 
desktop has an AMD processor and a nVidia video chipset and the laptop has an 
Intel processor and an Intel graphic controller.  Although I can't see how 
either the processor or video chipset would have anything to to with the USB 
or USB serial port-type devices.  The desktop also has a PCI quad serial port 
card and includes the 8250.nr_uarts=8 kernel option and is set up to use an 
analog dialup modem to make PPP connections (again, I don't see that as having 
anything to do with anything).

Both machines are running the same kernel: 2.6.32-573.12.1.el6.x86_64

At Thu, 4 Feb 2016 16:13:33 -0500 Robert Heller <heller at deepsoft.com> wrote:

> I have two computers: both running CentOS 6.7, 64-bit, with 
> kernel 2.6.32-573.12.1.el6.x86_64.  One is a laptop with an 2 core Intel 
> processor and the other is a desktop machine with a 4 core AMD processor. Both 
> with selinux enabled.
> I have a USB serial port device (a RR-CirKits LCC-Buffer USB).  On the desktop 
> I am getting this error:
> sauron.deepsoft.com% sudo minicom
> Device /dev/ttyACM0 access failed: No such file or directory.
> sauron.deepsoft.com% dir -lZ /dev/ttyACM0
> crw-rw----. root dialout system_u:object_r:tty_device_t:s0 /dev/ttyACM0
> But it is working on the laptop!
> gollum.deepsoft.com% dir -lZ /dev/ttyACM1
> crw-rw----. root dialout system_u:object_r:tty_device_t:s0 /dev/ttyACM1
> Same kernel, same device (except it is showing up as ttyACM1 on the laptop).
> What is going on here?

Robert Heller             -- 978-544-6933
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