Permission Denied ttyS0

Configuration
1

Home Assistant (5.11) Supervisor (2021.02.6) NUT (0.6.2) running on NUC
Eaton Powerwave 9130 ran excellent until last major upgrade, I receive this error in NUT addon when starting:

Network UPS Tools - BCMXCP UPS driver 0.31 (2.7.4)
RS-232 communication subdriver 0.20
Unable to open /dev/ttyS0: Operation not permitted
Current user id: root (0)
Serial port owner: root (0)
Mode of port: 0660
Things to try:

  • Use another port (with the right permissions)
  • Fix the port owner/group or permissions on this port
  • Run this driver as another user (upsdrvctl -u or ‘user=…’ in ups.conf).
    See upsdrvctl(8) and ups.conf(5).

ls -la /dev/ttyS0
crw-rw---- 1 root audio 4, 64 Feb 12 12:58 /dev/ttyS0

groups root
root bin daemon sys adm disk wheel floppy dialout tape video

I think the serial port needs to be in the dialout group for my NUT addon to access my UPS via serial cable.

How can I fix this permissions error?

Any help is appreciated.

2

what is the linux OS username your HA supervised is running under? I haven’t used that flavour since “hassio” and the username was homeassistant , but that might of all changed now.

anyway, get a login or ssh, as root

usermod -a -G audio,dialout <username>

e.g.

usermod -a -G audio,dialout homeassistant

but if root is the username, then it’s not permissions because root has full access to /dev/ttyS0 , more likely that is the wrong device name/doesn’t exist/kernel modules not loaded.

3

These commands are not available to me AFAIK.

4

I’m having similar issue after upgrading hassio host from 5.10 to 5.11, hassio addons can’t access serial ports. Example from SSH addon:

~ $ ls /dev/ttyS0  -la
crw-rw----    1 root     audio       4,  64 Feb 18 18:42 /dev/ttyS0
~ $ whoami
root
~ $ cat /dev/ttyS0
cat: can't open '/dev/ttyS0': Operation not permitted
~ $
5

This could be why.

6

The Upgrade to Supervisor 2021.03.3 fixed my issue.