Device ttyS0 is locked

When I use the sudo pon command I get this output.

pppd options in effect:
debug # (from /etc/ppp/peers/provider)
updetach # (from /etc/ppp/peers/provider)
dump # (from /etc/ppp/peers/provider)
noauth # (from /etc/ppp/peers/provider)
remotename 3gppp # (from /etc/ppp/peers/provider)
/dev/ttyS0 # (from /etc/ppp/peers/provider)
115200 # (from /etc/ppp/peers/provider)
lock # (from /etc/ppp/peers/provider)
connect chat -s -v -f /etc/chatscripts/chat-connect -T # (from /etc/ppp/peers/provider)
disconnect chat -s -v -f /etc/chatscripts/chat-disconnect # (from /etc/ppp/peers/provider)
nocrtscts # (from /etc/ppp/peers/provider)
modem # (from /etc/ppp/peers/provider)
asyncmap 0 # (from /etc/ppp/options)
lcp-echo-failure 4 # (from /etc/ppp/options)
lcp-echo-interval 30 # (from /etc/ppp/options)
hide-password # (from /etc/ppp/peers/provider)
novj # (from /etc/ppp/peers/provider)
novjccomp # (from /etc/ppp/peers/provider)
ipcp-accept-local # (from /etc/ppp/peers/provider)
ipcp-accept-remote # (from /etc/ppp/peers/provider)
ipparam 3gppp # (from /etc/ppp/peers/provider)
noipdefault # (from /etc/ppp/peers/provider)
ipcp-max-failure 30 # (from /etc/ppp/peers/provider)
defaultroute # (from /etc/ppp/peers/provider)
usepeerdns # (from /etc/ppp/peers/provider)
noccp # (from /etc/ppp/peers/provider)
noipx # (from /etc/ppp/options)
Device ttyS0 is locked by pid 2855

How do I get the ttys0 device to be unlocked thanks.

Do you have enabled the Serial port hardware and disabled login shell over serial?
It looks like ttys0 is being used by other services. You are getting this error because it is busy.


I do have the same issue.

  • Fresh install of Rasberry
  • I have enabled the Serial port hardware and disabled login shell over serial.
  • Did the SW install as described in the docs
  • get the error Device ttyS0 is locked by pid in sudo pon

Any other suggestion?

Hi @bart-9287,

You might have installed the reconnect service. For the time being, you can stop it till rebooting RPi or restarting the service manually: sudo systemctl stop reconnect.service

Now try sudo pon

Check, that gave me some more options, thanx
going to continue to setup


Sorry, no modem seen with modem manager

sudo mmcli -L
No modems were found


Hello, I hope you are well, I have seen this message and it has reminded me that I have a problem and I don’t know how to set up and create the service so that the connect script runs on my BBB, which is very similar to an RPi, could you show me the description of your *.service and in the 3G startup script, you put all the commands to turn on the modem and the call to put telephone company.
It would be very helpful and a little light, I’ve been fighting for days.
A smile