I've been getting some suggestions on how to figure out why my serial port is busy. Specifically, when I try to start gammu-smsd, it refuses to start on /dev/ttyS0 because it says that port is busy:
sudo /etc/init.d/gammu-smsd start
Sep 30 16:16:51 porkypig gammu-smsd[25355]: Starting phone communication...
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Gammu - 1.26.1 built 21:46:06 Nov 24 2009 using GCC 4.4]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Connection - "at115200"]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Connection index - 0]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Model type - ""]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Device - "/dev/ttyS0"]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [Runing on - Linux, kernel 2.6.32-42-server (#95-Ubuntu SMP Wed Jul 25 16:10:49 UTC 2012)]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: [System error - open in serial_open, 16, "Device or resource busy"]
Sep 30 16:16:51 porkypig gammu-smsd[25355]: gammu: Init:GSM_TryGetModel failed with error DEVICEOPENERROR[2]: Error opening device. Unknown, busy or no permissions.
Sep 30 16:16:51 porkypig gammu-smsd[25355]: Can't open device (Error opening device. Unknown, busy or no permissions.:2)
Sep 30 16:16:51 porkypig gammu-smsd[25355]: Using PGSQL service
Sep 30 16:16:51 porkypig gammu-smsd[25355]: Disconnecting from PostgreSQL
I used two different commands. Both of them find different processes culpable. First I try fuser:
fuser -m -u /dev/ttyS0
/dev/ttyS0: 21624(guarddoggps)
cd /proc/21624
cat status
Name: dropbox
State: S (sleeping)
Tgid: 21624
Pid: 21624
PPid: 1
TracerPid: 0
Uid: 1001 1001 1001 1001
Gid: 1001 1001 1001 1001
FDSize: 64
Groups: 5 27 1001 5004
VmPeak: 873732 kB
VmSize: 806040 kB
VmLck: 0 kB
VmHWM: 207668 kB
VmRSS: 131864 kB
VmData: 547820 kB
VmStk: 160 kB
VmExe: 3524 kB
VmLib: 29660 kB
VmPTE: 1244 kB
Threads: 21
SigQ: 0/16382
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000001001000
SigCgt: 00000001800004c8
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
Cpus_allowed: ff
Cpus_allowed_list: 0-7
Mems_allowed: 00000000,00000001
Mems_allowed_list: 0
voluntary_ctxt_switches: 202
nonvoluntary_ctxt_switches: 1
So fuser says dropbox is using it.
Then I use lsof:
sudo lsof | grep ttyS0
screen 23520 root 6u CHR 4,64 0t0 1421 /dev/ttyS0
lsof says screen (rather than dropbox) is using it.
So which of these programs (dropbox or screen) is really causing gammu-smsd to refuse to start because of the resourcing being "busy"?
Best Answer
The short answer is:
screen
.The slightly longer answer is that the
-m
flag tofuser
tells it to list everything using the mountpoint. Depending on your setup, that probably means all of/dev
, but it could also be/
. Clearly not what you intended. You'll get a very long list if you dofuser -vm /dev/ttyS0
, over 60 lines on my system.Take off the
-m
and it'll probably give you the same answer aslsof
did.