Serial port permission denied for non-root user with dialout group privileges
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Ubuntu |
New
|
Undecided
|
Unassigned |
Bug Description
lsb_release:
Description: Ubuntu 18.04 LTS
Release: 18.04
I write systemd services that launch with root privileges and de-privilege themselves to a system account (called mxdaemon). These services require access to the physical serial port (/dev/ttyS0) on the PC.
Serial port: crw-rw---- 1 root dialout 4, 64 Jun 13 22:00 /dev/ttyS0
When run as root, the service has no problem communicating via the serial port.
When the service is configured to de-privilege to mxdaemon, I get a permission denied error when attempting to access /dev/ttyS0.
mxdaemon is a member of both the dialout & tty groups: mxdaemon : mxdaemon dialout tty
Even after rebooting the PC, I still get permission denied for any user besides root.
Hours of scouring the Internet suggest that everything is configured correctly.
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