unlocking a serial device

Posted on 1998-02-22
Last Modified: 2012-08-13
Heya all!

Sometimes after i reboot my linux box a serial port or two
are locked for some reason.. and a file LCK..ttySx is created in /var/lock

Is there anyway to unlock this device so it's useable again ?

unlock /var/lock/LCK..ttySx doesn't work..  makes the computer THINK it's unlocked, but still doesn't work.

Is there another way I should be doing this?

Question by:Q010797
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Expert Comment

ID: 1636271
Delete the LCK file

Author Comment

ID: 1636272
that's the same as unlock /var/lock/{lock file}

no go.  I need some correct way of doing it

Expert Comment

ID: 1636273
Which daemons are running??
Do a 'ps -ax' and post it.
Learn by Doing. Anytime. Anywhere.

Do you like to learn by doing?
Our labs and exercises give you the chance to do just that: Learn by performing actions on real environments.

Hands-on, scenario-based labs give you experience on real environments provided by us so you don't have to worry about breaking anything.


Author Comment

ID: 1636274
I have to wait till the problem occurs again (only ever after a reboot) and I will paste the ps -ax here . .

Have just rebooted.. if I don't have locked tty's in an hour.. I won't have them at all . . makes sense right ? :)

Author Comment

ID: 1636275
at the moment . .ttyR7 is locked but it shouldn't be

120  ?  S    0:00 /usr/local/sbin/mgetty ttyR6 -n 1 -D -x2 -m "" ATZ OK
  121  ?  D    0:00 /usr/local/sbin/mgetty ttyR7 -n 1 -D -x2 -m "" ATZ OK
  122  ?  S    0:00 /usr/local/sbin/mgetty ttyS0 -n 1 -D -x2 -m "" ATZ OK
  123  ?  S    0:00 /usr/local/sbin/mgetty ttyS1 -n 1 -D -x2 -m "" ATZ OK
  124  ?  S    0:00 /usr/local/sbin/mgetty ttyS2 -n 1 -D -x2 -m "" ATZ OK
  125  ?  S    0:00 /usr/local/sbin/mgetty ttyS3 -n 1 -D -x2 -m "" ATZ OK

it has a D instead of an S next to it... this help anyone fix my problem?

Expert Comment

ID: 1636276
The only way to get a lock-file is to start a deamon which uses that port. The problem can, with other words, be a hanging process or a process with crashed.

If it only occurs during/after a reboot check your boot scripts for such kind of daemons.

Author Comment

ID: 1636277
Thing is... straight after the boot there will be no lock file for upto 30minutes..  and I assume it's mgetty that is hanging.  Why does it only do it sometimes? and why only after a reboot?  I don't usually have to reboot more than twice for it to go away.

Accepted Solution

luteijn earned 50 total points
ID: 1636278
Perhaps rebooting somehow upsets your modems, and some of them
start to babble endlessly with the getty, after a while confusing
eachother so much that they keep at it forever...
See if anything interesting is in your syslog (getty complaining
about what is send to it by the modem for instance)
Sometimes my modem does things like this when used for dialin,
I then just killed all the stuff interacting with it: kill -9 `ps |grep S2 |grep -v grep|awk '{printf $1}' `
removed the lock file: rm /var/spool/uucp/LCK..cua2, and reset the whole thing: stty crtscts < /dev/cua2 ; printf "+++at&Y0s0=4\n\r" >/dev/cua2

Featured Post

Don't Cry: How Liquid Web is Ensuring Security

WannaCry is just the start. Read how Liquid Web is protecting itself and its customers against new threats.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Network Interface Card (NIC) bonding, also known as link aggregation, NIC teaming and trunking, is an important concept to understand and implement in any environment where high availability is of concern. Using this feature, a server administrator …
How many times have you wanted to quickly do the same thing to a list but found yourself typing it again and again? I first figured out a small time saver with the up arrow to recall the last command but that can only get you so far if you have a bi…
Learn how to find files with the shell using the find and locate commands. Use locate to find a needle in a haystack.: With locate, check if the file still exists.: Use find to get the actual location of the file.:
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…

724 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question